Maintained by: NLnet Labs
unbound.conf(5)                  unbound 1.6.2                 unbound.conf(5)



NAME
       unbound.conf - Unbound configuration file.

SYNOPSIS
       unbound.conf

DESCRIPTION
       unbound.conf  is  used  to  configure  unbound(8).  The file format has
       attributes and values. Some attributes  have  attributes  inside  them.
       The notation is: attribute: value.

       Comments  start  with  #  and  last to the end of line. Empty lines are
       ignored as is whitespace at the beginning of a line.

       The utility unbound-checkconf(8) can  be  used  to  check  unbound.conf
       prior to usage.

EXAMPLE
       An    example    config   file   is   shown   below.   Copy   this   to
       /etc/unbound/unbound.conf and start the server with:

            $ unbound -c /etc/unbound/unbound.conf

       Most settings are the defaults. Stop the server with:

            $ kill `cat /etc/unbound/unbound.pid`

       Below is a minimal config file. The  source  distribution  contains  an
       extensive example.conf file with all the options.

       # unbound.conf(5) config file for unbound(8).
       server:
            directory: "/etc/unbound"
            username: unbound
            # make sure unbound can access entropy from inside the chroot.
            # e.g. on linux the use these commands (on BSD, devfs(8) is used):
            #      mount --bind -n /dev/random /etc/unbound/dev/random
            # and  mount --bind -n /dev/log /etc/unbound/dev/log
            chroot: "/etc/unbound"
            # logfile: "/etc/unbound/unbound.log"  #uncomment to use logfile.
            pidfile: "/etc/unbound/unbound.pid"
            # verbosity: 1      # uncomment and increase to get more logging.
            # listen on all interfaces, answer queries from the local subnet.
            interface: 0.0.0.0
            interface: ::0
            access-control: 10.0.0.0/8 allow
            access-control: 2001:DB8::/64 allow

FILE FORMAT
       There  must be whitespace between keywords. Attribute keywords end with
       a colon ':'. An attribute is followed by its containing attributes,  or
       a value.

       Files  can be included using the include: directive. It can appear any-
       where, it accepts a single file name as argument.  Processing continues
       as  if  the text from the included file was copied into the config file
       at that point.  If also using chroot, using full  path  names  for  the
       included files works, relative pathnames for the included names work if
       the directory where the daemon is  started  equals  its  chroot/working
       directory  or is specified before the include statement with directory:
       dir.  Wildcards can be used to include multiple files, see glob(7).

   Server Options
       These options are part of the server: clause.

       verbosity: <number>
              The verbosity number, level 0 means no verbosity,  only  errors.
              Level  1  gives  operational information. Level 2 gives detailed
              operational information. Level 3 gives query level  information,
              output  per  query.   Level 4 gives algorithm level information.
              Level 5 logs client identification for cache misses.  Default is
              level  1.  The verbosity can also be increased from the command-
              line, see unbound(8).

       statistics-interval: <seconds>
              The number of seconds between printing statistics to the log for
              every  thread.  Disable with value 0 or "". Default is disabled.
              The histogram statistics are only printed if replies  were  sent
              during  the  statistics  interval,  requestlist  statistics  are
              printed for every interval (but can be 0).  This is because  the
              median calculation requires data to be present.

       statistics-cumulative: <yes or no>
              If  enabled,  statistics  are cumulative since starting unbound,
              without clearing the statistics counters after logging the  sta-
              tistics. Default is no.

       extended-statistics: <yes or no>
              If  enabled,  extended  statistics are printed from unbound-con-
              trol(8).  Default is off, because keeping track of more  statis-
              tics takes time.  The counters are listed in unbound-control(8).

       num-threads: <number>
              The  number  of threads to create to serve clients. Use 1 for no
              threading.

       port: <port number>
              The port number, default 53, on which  the  server  responds  to
              queries.

       interface: <ip address[@port]>
              Interface  to  use  to connect to the network. This interface is
              listened to for queries from clients, and answers to clients are
              given  from  it.  Can be given multiple times to work on several
              interfaces. If none are given the default is to listen to local-
              host.   The  interfaces  are not changed on a reload (kill -HUP)
              but only on restart.  A port number can be specified with  @port
              (without spaces between interface and port number), if not spec-
              ified the default port (from port) is used.

       ip-address: <ip address[@port]>
              Same as interface: (for easy of compatibility with nsd.conf).

       interface-automatic: <yes or no>
              Detect source interface on UDP queries and copy them to replies.
              This  feature  is experimental, and needs support in your OS for
              particular socket options.  Default value is no.

       outgoing-interface: <ip address or ip6 netblock>
              Interface to use to connect to the network.  This  interface  is
              used  to send queries to authoritative servers and receive their
              replies. Can be given multiple times to work on  several  inter-
              faces.  If  none  are  given  the default (all) is used. You can
              specify the same interfaces in  interface:  and  outgoing-inter-
              face:  lines,  the  interfaces  are then used for both purposes.
              Outgoing queries are sent via a  random  outgoing  interface  to
              counter spoofing.

              If  an  IPv6 netblock is specified instead of an individual IPv6
              address, outgoing UDP  queries  will  use  a  randomised  source
              address  taken  from  the netblock to counter spoofing. Requires
              the IPv6 netblock to be routed to the host running unbound,  and
              requires  OS support for unprivileged non-local binds (currently
              only supported on Linux). Several  netblocks  may  be  specified
              with  multiple  outgoing-interface:  options, but do not specify
              both an individual IPv6 address and an  IPv6  netblock,  or  the
              randomisation will be compromised.  Consider combining with pre-
              fer-ip6: yes to increase  the  likelihood  of  IPv6  nameservers
              being  selected  for  queries.  On Linux you need these two com-
              mands to be able to use the freebind socket  option  to  receive
              traffic  for  the ip6 netblock: ip -6 addr add mynetblock/64 dev
              lo && ip -6 route add local mynetblock/64 dev lo

       outgoing-range: <number>
              Number of ports to open. This number of file descriptors can  be
              opened  per  thread. Must be at least 1. Default depends on com-
              pile options. Larger numbers need extra resources from the oper-
              ating  system.   For performance a very large value is best, use
              libevent to make this possible.

       outgoing-port-permit: <port number or range>
              Permit unbound to open this port or range of ports  for  use  to
              send  queries.   A  larger  number  of  permitted outgoing ports
              increases resilience against spoofing attempts. Make sure  these
              ports  are  not  needed by other daemons.  By default only ports
              above 1024 that have not been assigned by IANA are used.  Give a
              port number or a range of the form "low-high", without spaces.

              The  outgoing-port-permit and outgoing-port-avoid statements are
              processed in the line order of the config file, adding the  per-
              mitted  ports  and subtracting the avoided ports from the set of
              allowed ports.  The processing starts with the  non  IANA  allo-
              cated ports above 1024 in the set of allowed ports.

       outgoing-port-avoid: <port number or range>
              Do  not  permit  unbound to open this port or range of ports for
              use to send queries. Use this to make sure unbound does not grab
              a  port  that  another  daemon needs. The port is avoided on all
              outgoing interfaces, both IP4 and IP6.  By  default  only  ports
              above 1024 that have not been assigned by IANA are used.  Give a
              port number or a range of the form "low-high", without spaces.

       outgoing-num-tcp: <number>
              Number of outgoing TCP buffers to allocate per  thread.  Default
              is  10.  If  set  to  0, or if do-tcp is "no", no TCP queries to
              authoritative  servers  are  done.   For  larger   installations
              increasing this value is a good idea.

       incoming-num-tcp: <number>
              Number  of  incoming TCP buffers to allocate per thread. Default
              is 10. If set to 0, or if do-tcp is "no", no  TCP  queries  from
              clients  are  accepted. For larger installations increasing this
              value is a good idea.

       edns-buffer-size: <number>
              Number of bytes size to advertise as the EDNS reassembly  buffer
              size.   This  is  the  value put into datagrams over UDP towards
              peers.  The actual buffer size is determined by  msg-buffer-size
              (both  for  TCP  and  UDP).   Do not set higher than that value.
              Default is 4096 which is RFC recommended.  If you have  fragmen-
              tation  reassembly  problems,  usually  seen as timeouts, then a
              value of 1480 can fix it.  Setting to 512 bypasses even the most
              stringent  path  MTU problems, but is seen as extreme, since the
              amount of TCP fallback generated is excessive (probably also for
              this resolver, consider tuning the outgoing tcp number).

       max-udp-size: <number>
              Maximum  UDP response size (not applied to TCP response).  65536
              disables the udp response size maximum, and uses the choice from
              the  client,  always.  Suggested values are 512 to 4096. Default
              is 4096.

       msg-buffer-size: <number>
              Number of bytes size of the message buffers.  Default  is  65552
              bytes,  enough  for 64 Kb packets, the maximum DNS message size.
              No message larger than this can be  sent  or  received.  Can  be
              reduced to use less memory, but some requests for DNS data, such
              as for huge resource records, will result in a SERVFAIL reply to
              the client.

       msg-cache-size: <number>
              Number  of  bytes  size  of  the  message  cache.  Default  is 4
              megabytes.  A plain number is in bytes, append 'k', 'm'  or  'g'
              for  kilobytes,  megabytes  or  gigabytes  (1024*1024 bytes in a
              megabyte).

       msg-cache-slabs: <number>
              Number of slabs in the message cache.  Slabs  reduce  lock  con-
              tention  by  threads.   Must  be  set  to  a power of 2. Setting
              (close) to the number of cpus is a reasonable guess.

       num-queries-per-thread: <number>
              The number of queries that every thread will service  simultane-
              ously.   If  more  queries  arrive  that  need servicing, and no
              queries can  be  jostled  out  (see  jostle-timeout),  then  the
              queries  are  dropped.  This forces the client to resend after a
              timeout; allowing the  server  time  to  work  on  the  existing
              queries. Default depends on compile options, 512 or 1024.

       jostle-timeout: <msec>
              Timeout  used when the server is very busy.  Set to a value that
              usually results in one roundtrip to the authority  servers.   If
              too  many queries arrive, then 50% of the queries are allowed to
              run to completion, and the other 50% are replaced with  the  new
              incoming  query  if  they  have  already  spent  more than their
              allowed time.  This protects against denial of service  by  slow
              queries  or  high  query  rates.  Default 200 milliseconds.  The
              effect is that the qps for long-lasting queries is  about  (num-
              queriesperthread  /  2)  /  (average time for such long queries)
              qps.  The qps  for  short  queries  can  be  about  (numqueries-
              perthread  /  2)  /  (jostletimeout  in  whole  seconds) qps per
              thread, about (1024/2)*5 = 2560 qps by default.

       delay-close: <msec>
              Extra delay for timeouted UDP ports before they are  closed,  in
              msec.   Default  is 0, and that disables it.  This prevents very
              delayed answer packets from  the  upstream  (recursive)  servers
              from  bouncing  against closed ports and setting off all sort of
              close-port counters, with eg. 1500 msec.  When  timeouts  happen
              you  need extra sockets, it checks the ID and remote IP of pack-
              ets, and unwanted packets  are  added  to  the  unwanted  packet
              counter.

       so-rcvbuf: <number>
              If  not 0, then set the SO_RCVBUF socket option to get more buf-
              fer space on UDP port 53 incoming queries.  So that short spikes
              on  busy  servers  do  not  drop packets (see counter in netstat
              -su).  Default is 0 (use system value).  Otherwise,  the  number
              of  bytes to ask for, try "4m" on a busy server.  The OS caps it
              at a maximum, on linux unbound needs root permission  to  bypass
              the  limit,  or  the admin can use sysctl net.core.rmem_max.  On
              BSD change kern.ipc.maxsockbuf in /etc/sysctl.conf.  On  OpenBSD
              change header and recompile kernel. On Solaris ndd -set /dev/udp
              udp_max_buf 8388608.

       so-sndbuf: <number>
              If not 0, then set the SO_SNDBUF socket option to get more  buf-
              fer  space  on UDP port 53 outgoing queries.  This for very busy
              servers handles  spikes  in  answer  traffic,  otherwise  'send:
              resource  temporarily  unavailable'  can  get logged, the buffer
              overrun is also visible by netstat -su.  Default is 0 (use  sys-
              tem value).  Specify the number of bytes to ask for, try "4m" on
              a very busy server.  The OS caps  it  at  a  maximum,  on  linux
              unbound  needs root permission to bypass the limit, or the admin
              can use sysctl net.core.wmem_max.  On BSD, Solaris  changes  are
              similar to so-rcvbuf.

       so-reuseport: <yes or no>
              If  yes,  then  open  dedicated  listening  sockets for incoming
              queries for each thread and try to set the  SO_REUSEPORT  socket
              option  on  each  socket.   May  distribute  incoming queries to
              threads more evenly.  Default is no.  On Linux it  is  supported
              in  kernels  >= 3.9.  On other systems, FreeBSD, OSX it may also
              work.  You can enable it (on any platform and kernel),  it  then
              attempts to open the port and passes the option if it was avail-
              able at compile time, if that works it is used, if it fails,  it
              continues silently (unless verbosity 3) without the option.

       ip-transparent: <yes or no>
              If  yes,  then use IP_TRANSPARENT socket option on sockets where
              unbound is listening for incoming traffic.  Default no.   Allows
              you  to bind to non-local interfaces.  For example for non-exis-
              tant IP addresses that are going to exist later  on,  with  host
              failover configuration.  This is a lot like interface-automatic,
              but that one services all interfaces and with  this  option  you
              can  select  which  (future) interfaces unbound provides service
              on.  This option needs unbound to be started with  root  permis-
              sions  on  some  systems.  The option uses IP_BINDANY on FreeBSD
              systems.

       ip-freebind: <yes or no>
              If yes, then use IP_FREEBIND  socket  option  on  sockets  where
              unbound  is  listening to incoming traffic.  Default no.  Allows
              you to bind to IP addresses that are nonlocal or do  not  exist,
              like  when  the network interface or IP address is down.  Exists
              only on Linux, where the similar ip-transparent option  is  also
              available.

       rrset-cache-size: <number>
              Number of bytes size of the RRset cache. Default is 4 megabytes.
              A plain number is in bytes, append 'k', 'm'  or  'g'  for  kilo-
              bytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).

       rrset-cache-slabs: <number>
              Number of slabs in the RRset cache. Slabs reduce lock contention
              by threads.  Must be set to a power of 2.

       cache-max-ttl: <seconds>
              Time to live maximum for  RRsets  and  messages  in  the  cache.
              Default  is  86400  seconds  (1  day).  If the maximum kicks in,
              responses to clients still get decrementing TTLs  based  on  the
              original  (larger)  values.   When the internal TTL expires, the
              cache item has expired.  Can be set lower to force the  resolver
              to query for data often, and not trust (very large) TTL values.

       cache-min-ttl: <seconds>
              Time  to  live  minimum  for  RRsets  and messages in the cache.
              Default is 0.  If the minimum kicks in, the data is  cached  for
              longer than the domain owner intended, and thus less queries are
              made to look up the data.  Zero makes sure the data in the cache
              is  as the domain owner intended, higher values, especially more
              than an hour or so, can lead to trouble as the data in the cache
              does not match up with the actual data any more.

       cache-max-negative-ttl: <seconds>
              Time to live maximum for negative responses, these have a SOA in
              the authority section that is limited in time.  Default is 3600.

       infra-host-ttl: <seconds>
              Time to live for entries in the host cache. The host cache  con-
              tains  roundtrip  timing, lameness and EDNS support information.
              Default is 900.

       infra-cache-slabs: <number>
              Number of slabs in the infrastructure cache. Slabs  reduce  lock
              contention by threads. Must be set to a power of 2.

       infra-cache-numhosts: <number>
              Number  of  hosts  for  which  information is cached. Default is
              10000.

       infra-cache-min-rtt: <msec>
              Lower limit for dynamic retransmit timeout calculation in infra-
              structure cache. Default is 50 milliseconds. Increase this value
              if using forwarders needing more time to do recursive name reso-
              lution.

       define-tag: <"list of tags">
              Define the tags that can be used with local-zone and access-con-
              trol.  Enclose the list  between  quotes  ("")  and  put  spaces
              between tags.

       do-ip4: <yes or no>
              Enable  or  disable  whether ip4 queries are answered or issued.
              Default is yes.

       do-ip6: <yes or no>
              Enable or disable whether ip6 queries are  answered  or  issued.
              Default  is yes.  If disabled, queries are not answered on IPv6,
              and queries are not sent on IPv6 to  the  internet  nameservers.
              With  this option you can disable the ipv6 transport for sending
              DNS traffic, it does not impact the contents of the DNS traffic,
              which may have ip4 and ip6 addresses in it.

       prefer-ip6: <yes or no>
              If  enabled,  prefer  IPv6  transport for sending DNS queries to
              internet nameservers. Default is no.

       do-udp: <yes or no>
              Enable or disable whether UDP queries are  answered  or  issued.
              Default is yes.

       do-tcp: <yes or no>
              Enable  or  disable  whether TCP queries are answered or issued.
              Default is yes.

       tcp-mss: <number>
              Maximum segment size (MSS) of TCP socket  on  which  the  server
              responds  to  queries.  Value  lower than common MSS on Ethernet
              (1220 for example) will address path MTU problem.  Note that not
              all  platform  supports  socket  option to set MSS (TCP_MAXSEG).
              Default is system default MSS determined by  interface  MTU  and
              negotiation between server and client.

       outgoing-tcp-mss: <number>
              Maximum  segment  size  (MSS) of TCP socket for outgoing queries
              (from Unbound to other servers). Value lower than common MSS  on
              Ethernet (1220 for example) will address path MTU problem.  Note
              that  not  all  platform  supports  socket  option  to  set  MSS
              (TCP_MAXSEG).   Default  is  system  default  MSS  determined by
              interface MTU and negotiation between Unbound and other servers.

       tcp-upstream: <yes or no>
              Enable or disable whether the upstream queries use TCP only  for
              transport.  Default is no.  Useful in tunneling scenarios.

       ssl-upstream: <yes or no>
              Enabled or disable whether the upstream queries use SSL only for
              transport.  Default is no.  Useful in tunneling scenarios.   The
              SSL contains plain DNS in TCP wireformat.  The other server must
              support this (see ssl-service-key).

       ssl-service-key: <file>
              If enabled, the server provider SSL service on its TCP  sockets.
              The clients have to use ssl-upstream: yes.  The file is the pri-
              vate key for the TLS session.  The public certificate is in  the
              ssl-service-pem  file.   Default  is "", turned off.  Requires a
              restart (a reload is not enough) if changed, because the private
              key  is  read  while root permissions are held and before chroot
              (if any).  Normal DNS TCP service  is  not  provided  and  gives
              errors,  this  service is best run with a different port: config
              or @port suffixes in the interface config.

       ssl-service-pem: <file>
              The public  key  certificate  pem  file  for  the  ssl  service.
              Default is "", turned off.

       ssl-port: <number>
              The  port  number  on  which to provide TCP SSL service, default
              853, only interfaces configured with that port number as @number
              get the SSL service.

       use-systemd: <yes or no>
              Enable or disable systemd socket activation.  Default is no.

       do-daemonize: <yes or no>
              Enable  or  disable  whether  the  unbound server forks into the
              background as a daemon.  Set the value to no when  unbound  runs
              as systemd service.  Default is yes.

       access-control: <IP netblock> <action>
              The  netblock  is  given  as  an  IP4  or IP6 address with /size
              appended for a classless network block. The action can be  deny,
              refuse,  allow, allow_snoop, deny_non_local or refuse_non_local.
              The most specific netblock match is used, if none match deny  is
              used.

              The action deny stops queries from hosts from that netblock.

              The  action  refuse  stops  queries  too,  but sends a DNS rcode
              REFUSED error message back.

              The action allow gives access to clients from that netblock.  It
              gives  only  access  for recursion clients (which is what almost
              all clients need).  Nonrecursive queries are refused.

              The allow action does allow nonrecursive queries to  access  the
              local-data that is configured.  The reason is that this does not
              involve the  unbound  server  recursive  lookup  algorithm,  and
              static data is served in the reply.  This supports normal opera-
              tions where nonrecursive queries are made for the  authoritative
              data.   For  nonrecursive  queries  any replies from the dynamic
              cache are refused.

              The action allow_snoop gives nonrecursive access too.  This give
              both  recursive  and non recursive access.  The name allow_snoop
              refers to  cache  snooping,  a  technique  to  use  nonrecursive
              queries  to  examine  the  cache  contents (for malicious acts).
              However, nonrecursive queries can also be a  valuable  debugging
              tool (when you want to examine the cache contents). In that case
              use allow_snoop for your administration host.

              By default only localhost is allowed, the rest is refused.   The
              default  is  refused, because that is protocol-friendly. The DNS
              protocol is not designed to handle dropped packets due  to  pol-
              icy,  and  dropping  may  result in (possibly excessive) retried
              queries.

              The deny_non_local and refuse_non_local settings are  for  hosts
              that are only allowed to query for the authoritative local-data,
              they are not allowed full recursion but only  the  static  data.
              With  deny_non_local,  messages that are disallowed are dropped,
              with refuse_non_local they receive error code REFUSED.

       access-control-tag: <IP netblock> <"list of tags">
              Assign tags  to  access-control  elements.  Clients  using  this
              access  control  element use localzones that are tagged with one
              of these tags. Tags must be  defined  in  define-tags.   Enclose
              list  of  tags  in  quotes  ("") and put spaces between tags. If
              access-control-tag is configured for a netblock  that  does  not
              have  an  access-control,  an access-control element with action
              allow is configured for this netblock.

       access-control-tag-action: <IP netblock> <tag> <action>
              Set action for particular tag for given access control  element.
              If  you  have  multiple  tag  values, the tag used to lookup the
              action is the first tag  match  between  access-control-tag  and
              local-zone-tag where "first" comes from the order of the define-
              tag values.

       access-control-tag-data: <IP netblock> <tag> <"resource record string">
              Set redirect data for particular tag for  given  access  control
              element.

       access-control-view: <IP netblock> <view name>
              Set view for given access control element.

       chroot: <directory>
              If  chroot  is enabled, you should pass the configfile (from the
              commandline) as a full path from the original  root.  After  the
              chroot  has been performed the now defunct portion of the config
              file path is removed to be able to reread  the  config  after  a
              reload.

              All  other  file paths (working dir, logfile, roothints, and key
              files) can be specified in several ways:  as  an  absolute  path
              relative  to  the  new  root,  as a relative path to the working
              directory, or as an absolute path relative to the original root.
              In  the last case the path is adjusted to remove the unused por-
              tion.

              The pidfile can be either a relative path to the working  direc-
              tory,  or  an absolute path relative to the original root. It is
              written just prior to  chroot  and  dropping  permissions.  This
              allows  the pidfile to be /var/run/unbound.pid and the chroot to
              be /var/unbound, for example.

              Additionally,  unbound  may  need  to  access  /dev/random  (for
              entropy) from inside the chroot.

              If given a chroot is done to the given directory. The default is
              "/usr/local/etc/unbound". If you give "" no chroot is performed.

       username: <name>
              If given,  after  binding  the  port  the  user  privileges  are
              dropped.  Default is "unbound". If you give username: "" no user
              change is performed.

              If this user is not capable of binding  the  port,  reloads  (by
              signal  HUP)  will still retain the opened ports.  If you change
              the port number in the config file, and  that  new  port  number
              requires  privileges,  then  a  reload  will  fail; a restart is
              needed.

       directory: <directory>
              Sets  the  working  directory  for  the  program.   Default   is
              "/usr/local/etc/unbound".   On Windows the string "%EXECUTABLE%"
              tries to change to the directory that  unbound.exe  resides  in.
              If you give a server: directory: dir before include: file state-
              ments then those includes can be relative to the working  direc-
              tory.

       logfile: <filename>
              If  ""  is given, logging goes to stderr, or nowhere once daemo-
              nized.  The logfile is appended to, in the following format:
              [seconds since 1970] unbound[pid:tid]: type: message.
              If this option is given, the use-syslog  is  option  is  set  to
              "no".  The logfile is reopened (for append) when the config file
              is reread, on SIGHUP.

       use-syslog: <yes or no>
              Sets unbound to send log messages to  the  syslogd,  using  sys-
              log(3).   The  log  facility  LOG_DAEMON  is used, with identity
              "unbound".  The logfile setting is overridden when use-syslog is
              turned on.  The default is to log to syslog.

       log-identity: <string>
              If  "" is given (default), then the name of the executable, usu-
              ally "unbound" is used to report to the log.  Enter a string  to
              override  it with that, which is useful on systems that run more
              than one instance of unbound, with different configurations,  so
              that the logs can be easily distinguished against.

       log-time-ascii: <yes or no>
              Sets  logfile  lines to use a timestamp in UTC ascii. Default is
              no, which prints the seconds since 1970 in brackets.  No  effect
              if  using  syslog,  in  that  case  syslog formats the timestamp
              printed into the log files.

       log-queries: <yes or no>
              Prints one line per query to the log, with the log timestamp and
              IP  address, name, type and class.  Default is no.  Note that it
              takes time to print these lines which makes the server (signifi-
              cantly)  slower.   Odd  (nonprintable)  characters  in names are
              printed as '?'.

       log-replies: <yes or no>
              Prints one line per reply to the log, with the log timestamp and
              IP  address,  name,  type,  class, return code, time to resolve,
              from cache and response size.  Default  is  no.   Note  that  it
              takes time to print these lines which makes the server (signifi-
              cantly) slower.  Odd  (nonprintable)  characters  in  names  are
              printed as '?'.

       pidfile: <filename>
              The   process   id   is   written   to   the  file.  Default  is
              "/usr/local/etc/unbound/unbound.pid".  So,
              kill -HUP `cat /usr/local/etc/unbound/unbound.pid`
              triggers a reload,
              kill -TERM `cat /usr/local/etc/unbound/unbound.pid`
              gracefully terminates.

       root-hints: <filename>
              Read the root hints from this file. Default  is  nothing,  using
              builtin  hints for the IN class. The file has the format of zone
              files, with  root  nameserver  names  and  addresses  only.  The
              default  may  become outdated, when servers change, therefore it
              is good practice to use a root-hints file.

       hide-identity: <yes or no>
              If enabled id.server and hostname.bind queries are refused.

       identity: <string>
              Set the identity to report. If set to "", the default, then  the
              hostname of the server is returned.

       hide-version: <yes or no>
              If enabled version.server and version.bind queries are refused.

       version: <string>
              Set  the  version to report. If set to "", the default, then the
              package version is returned.

       hide-trustanchor: <yes or no>
              If enabled trustanchor.unbound queries are refused.

       target-fetch-policy: <"list of numbers">
              Set the target fetch policy used by unbound to determine  if  it
              should  fetch nameserver target addresses opportunistically. The
              policy is described per dependency depth.

              The number of values determines  the  maximum  dependency  depth
              that  unbound  will  pursue in answering a query.  A value of -1
              means to fetch all targets opportunistically for that dependency
              depth.  A  value  of 0 means to fetch on demand only. A positive
              value fetches that many targets opportunistically.

              Enclose the list between quotes ("") and put spaces between num-
              bers.   The default is "3 2 1 0 0". Setting all zeroes, "0 0 0 0
              0" gives behaviour closer to that of BIND 9, while  setting  "-1
              -1  -1  -1  -1" gives behaviour rumoured to be closer to that of
              BIND 8.

       harden-short-bufsize: <yes or no>
              Very small EDNS buffer sizes from queries are  ignored.  Default
              is  off,  since  it  is  legal  protocol wise to send these, and
              unbound tries to give very small answers to these queries, where
              possible.

       harden-large-queries: <yes or no>
              Very  large  queries  are  ignored.  Default is off, since it is
              legal protocol wise to send these, and could  be  necessary  for
              operation if TSIG or EDNS payload is very large.

       harden-glue: <yes or no>
              Will  trust  glue  only  if  it is within the servers authority.
              Default is on.

       harden-dnssec-stripped: <yes or no>
              Require DNSSEC data for trust-anchored zones, if  such  data  is
              absent,  the  zone  becomes  bogus. If turned off, and no DNSSEC
              data is received (or the DNSKEY data fails  to  validate),  then
              the  zone  is made insecure, this behaves like there is no trust
              anchor. You could turn this off if you are sometimes  behind  an
              intrusive  firewall (of some sort) that removes DNSSEC data from
              packets, or a zone changes from  signed  to  unsigned  to  badly
              signed  often.  If  turned  off  you run the risk of a downgrade
              attack that disables security for a zone. Default is on.

       harden-below-nxdomain: <yes or no>
              From RFC 8020 (with title "NXDOMAIN:  There  Really  Is  Nothing
              Underneath"),  returns  nxdomain  to  queries  for  a name below
              another name that is already known to be nxdomain.  DNSSEC  man-
              dates  noerror  for  empty nonterminals, hence this is possible.
              Very old software might return nxdomain for  empty  nonterminals
              (that  usually  happen for reverse IP address lookups), and thus
              may be incompatible with  this.   To  try  to  avoid  this  only
              DNSSEC-secure  nxdomains are used, because the old software does
              not have DNSSEC.  Default is off.  The nxdomain must be  secure,
              this means nsec3 with optout is insufficient.

       harden-referral-path: <yes or no>
              Harden  the  referral  path by performing additional queries for
              infrastructure data.  Validates the replies if trust anchors are
              configured and the zones are signed.  This enforces DNSSEC vali-
              dation on nameserver NS sets and the nameserver  addresses  that
              are  encountered  on  the  referral path to the answer.  Default
              off, because it burdens the authority servers, and it is not RFC
              standard,  and could lead to performance problems because of the
              extra query load that is generated.   Experimental  option.   If
              you  enable  it  consider  adding  more  numbers  after the tar-
              get-fetch-policy to increase the max depth that is checked to.

       harden-algo-downgrade: <yes or no>
              Harden against algorithm downgrade when multiple algorithms  are
              advertised  in  the  DS record.  If no, allows the weakest algo-
              rithm to validate the zone.  Default is no.  Zone  signers  must
              produce  zones  that  allow  this feature to work, but sometimes
              they do not, and turning this option off avoids that  validation
              failure.

       use-caps-for-id: <yes or no>
              Use  0x20-encoded  random  bits  in  the  query  to  foil  spoof
              attempts.  This perturbs the lowercase and  uppercase  of  query
              names  sent  to  authority servers and checks if the reply still
              has the correct casing.  Disabled by default.  This  feature  is
              an experimental implementation of draft dns-0x20.

       caps-whitelist: <domain>
              Whitelist  the  domain  so  that it does not receive caps-for-id
              perturbed queries.  For domains that do  not  support  0x20  and
              also  fail  with  fallback  because  they keep sending different
              answers, like some load balancers.  Can be given multiple times,
              for different domains.

       qname-minimisation: <yes or no>
              Send  minimum  amount  of  information  to  upstream  servers to
              enhance privacy.  Only sent minimum required labels of the QNAME
              and  set  QTYPE  to NS when possible. Best effort approach; full
              QNAME and original QTYPE will be sent when upstream replies with
              a  RCODE other than NOERROR, except when receiving NXDOMAIN from
              a DNSSEC signed zone. Default is off.

       qname-minimisation-strict: <yes or no>
              QNAME minimisation in strict mode. Do not fall-back  to  sending
              full  QNAME  to potentially broken nameservers. A lot of domains
              will not be resolvable when this option in enabled. Only use  if
              you  know  what you are doing.  This option only has effect when
              qname-minimisation is enabled. Default is off.

       private-address: <IP address or subnet>
              Give IPv4 of IPv6 addresses  or  classless  subnets.  These  are
              addresses  on  your  private  network, and are not allowed to be
              returned for public internet  names.   Any  occurrence  of  such
              addresses are removed from DNS answers. Additionally, the DNSSEC
              validator may mark the  answers  bogus.  This  protects  against
              so-called  DNS  Rebinding, where a user browser is turned into a
              network proxy, allowing remote access  through  the  browser  to
              other  parts of your private network.  Some names can be allowed
              to contain your private addresses, by default all the local-data
              that  you  configured  is  allowed to, and you can specify addi-
              tional names using private-domain.   No  private  addresses  are
              enabled  by default.  We consider to enable this for the RFC1918
              private IP address space by  default  in  later  releases.  That
              would  enable  private  addresses  for  10.0.0.0/8 172.16.0.0/12
              192.168.0.0/16 169.254.0.0/16 fd00::/8 and fe80::/10, since  the
              RFC  standards  say these addresses should not be visible on the
              public internet.  Turning on 127.0.0.0/8 would hinder many spam-
              blocklists   as  they  use  that.   Adding  ::ffff:0:0/96  stops
              IPv4-mapped IPv6 addresses from bypassing the filter.

       private-domain: <domain name>
              Allow this domain, and all its  subdomains  to  contain  private
              addresses.   Give  multiple times to allow multiple domain names
              to contain private addresses. Default is none.

       unwanted-reply-threshold: <number>
              If set, a total number of unwanted replies is kept track  of  in
              every thread.  When it reaches the threshold, a defensive action
              is taken and a warning is printed to  the  log.   The  defensive
              action  is  to  clear  the  rrset  and message caches, hopefully
              flushing away any poison.  A value of 10 million  is  suggested.
              Default is 0 (turned off).

       do-not-query-address: <IP address>
              Do  not  query  the  given IP address. Can be IP4 or IP6. Append
              /num to indicate a classless delegation  netblock,  for  example
              like 10.2.3.4/24 or 2001::11/64.

       do-not-query-localhost: <yes or no>
              If  yes, localhost is added to the do-not-query-address entries,
              both IP6 ::1 and IP4 127.0.0.1/8. If no, then localhost  can  be
              used to send queries to. Default is yes.

       prefetch: <yes or no>
              If yes, message cache elements are prefetched before they expire
              to keep the cache up to date.  Default is  no.   Turning  it  on
              gives about 10 percent more traffic and load on the machine, but
              popular items do not expire from the cache.

       prefetch-key: <yes or no>
              If yes, fetch the DNSKEYs earlier  in  the  validation  process,
              when  a  DS  record  is encountered.  This lowers the latency of
              requests.  It does use a little more CPU.  Also if the cache  is
              set to 0, it is no use. Default is no.

       rrset-roundrobin: <yes or no>
              If yes, Unbound rotates RRSet order in response (the random num-
              ber is taken from the query ID, for speed  and  thread  safety).
              Default is no.

       minimal-responses: <yes or no>
              If  yes,  Unbound  doesn't  insert authority/additional sections
              into response messages when those  sections  are  not  required.
              This  reduces  response  size  significantly,  and may avoid TCP
              fallback for some responses.  This may cause a  slight  speedup.
              The  default  is no, because the DNS protocol RFCs mandate these
              sections, and the additional content could be of  use  and  save
              roundtrips for clients.

       disable-dnssec-lame-check: <yes or no>
              If  true,  disables  the  DNSSEC lameness check in the iterator.
              This check sees if RRSIGs are present in the answer, when dnssec
              is  expected,  and retries another authority if RRSIGs are unex-
              pectedly missing.  The  validator  will  insist  in  RRSIGs  for
              DNSSEC  signed  domains  regardless  of this setting, if a trust
              anchor is loaded.

       module-config: <"module names">
              Module configuration, a list of module names separated  by  spa-
              ces,  surround  the  string with quotes (""). The modules can be
              validator, iterator.  Setting this to "iterator" will result  in
              a  non-validating  server.  Setting this to "validator iterator"
              will turn on DNSSEC validation.  The ordering of the modules  is
              important.  You must also set trust-anchors for validation to be
              useful.

       trust-anchor-file: <filename>
              File with trusted  keys  for  validation.  Both  DS  and  DNSKEY
              entries  can  appear  in the file. The format of the file is the
              standard DNS Zone file format.   Default  is  "",  or  no  trust
              anchor file.

       auto-trust-anchor-file: <filename>
              File  with  trust  anchor  for  one  zone, which is tracked with
              RFC5011 probes.  The probes are several times  per  month,  thus
              the  machine must be online frequently.  The initial file can be
              one with contents as described in trust-anchor-file.   The  file
              is  written  to  when the anchor is updated, so the unbound user
              must have write permission.  Write permission to the  file,  but
              also  to  the  directory  it  is in (to create a temporary file,
              which is necessary to deal with filesystem full events), it must
              also be inside the chroot (if that is used).

       trust-anchor: <"Resource Record">
              A  DS  or  DNSKEY  RR  for a key to use for validation. Multiple
              entries can be given to specify multiple trusted keys, in  addi-
              tion  to the trust-anchor-files.  The resource record is entered
              in the same format as 'dig' or 'drill'  prints  them,  the  same
              format  as in the zone file. Has to be on a single line, with ""
              around it. A TTL can be specified for ease of cut and paste, but
              is ignored.  A class can be specified, but class IN is default.

       trusted-keys-file: <filename>
              File  with  trusted  keys  for validation. Specify more than one
              file  with  several  entries,   one   file   per   entry.   Like
              trust-anchor-file  but  has  a  different file format. Format is
              BIND-9 style format, the trusted-keys {  name  flag  proto  algo
              "key";  };  clauses  are  read.  It is possible to use wildcards
              with this statement, the wildcard is expanded on  start  and  on
              reload.

       dlv-anchor-file: <filename>
              This option was used during early days DNSSEC deployment when no
              parent-side  DS  record  registrations  were  easily  available.
              Nowadays, it is best to have DS records registered with the par-
              ent zone (many top level zones are signed).  File  with  trusted
              keys  for  DLV (DNSSEC Lookaside Validation). Both DS and DNSKEY
              entries can be used in the file,  in  the  same  format  as  for
              trust-anchor-file:  statements.  Only one DLV can be configured,
              more would be slow. The DLV configured is used as a root trusted
              DLV,  this means that it is a lookaside for the root. Default is
              "", or no dlv anchor file.  DLV is going to  be  decommissioned.
              Please do not use it any more.

       dlv-anchor: <"Resource Record">
              Much  like  trust-anchor,  this  is  a DLV anchor with the DS or
              DNSKEY inline.  DLV is going to be  decommissioned.   Please  do
              not use it any more.

       domain-insecure: <domain name>
              Sets  domain  name  to  be  insecure,  DNSSEC  chain of trust is
              ignored towards the domain name.  So a trust  anchor  above  the
              domain  name  can  not  make the domain secure with a DS record,
              such a DS record is  then  ignored.   Also  keys  from  DLV  are
              ignored  for the domain.  Can be given multiple times to specify
              multiple domains that are treated as if unsigned.   If  you  set
              trust anchors for the domain they override this setting (and the
              domain is secured).

              This can be useful if you want to make sure a trust  anchor  for
              external  lookups does not affect an (unsigned) internal domain.
              A DS record externally can create validation failures  for  that
              internal domain.

       val-override-date: <rrsig-style date spec>
              Default  is "" or "0", which disables this debugging feature. If
              enabled by giving a RRSIG style date, that date is used for ver-
              ifying RRSIG inception and expiration dates, instead of the cur-
              rent date. Do not set this unless you  are  debugging  signature
              inception  and  expiration.  The value -1 ignores the date alto-
              gether, useful for some special applications.

       val-sig-skew-min: <seconds>
              Minimum number of seconds of clock skew to  apply  to  validated
              signatures.   A  value of 10% of the signature lifetime (expira-
              tion - inception) is used, capped by this setting.   Default  is
              3600  (1  hour)  which  allows for daylight savings differences.
              Lower this value for more strict checking of short lived  signa-
              tures.

       val-sig-skew-max: <seconds>
              Maximum  number  of  seconds of clock skew to apply to validated
              signatures.  A value of 10% of the signature  lifetime  (expira-
              tion  -  inception) is used, capped by this setting.  Default is
              86400 (24 hours) which allows for timezone setting  problems  in
              stable  domains.  Setting both min and max very low disables the
              clock skew allowances.  Setting both min and max very high makes
              the validator check the signature timestamps less strictly.

       val-bogus-ttl: <number>
              The  time  to  live for bogus data. This is data that has failed
              validation; due to invalid signatures or other checks.  The  TTL
              from  that  data  cannot  be  trusted,  and  this  value is used
              instead. The value is in seconds, default 60.  The time interval
              prevents repeated revalidation of bogus data.

       val-clean-additional: <yes or no>
              Instruct  the  validator to remove data from the additional sec-
              tion of secure messages that are not signed  properly.  Messages
              that  are  insecure,  bogus,  indeterminate or unchecked are not
              affected. Default is yes. Use this setting to protect the  users
              that  rely on this validator for authentication from potentially
              bad data in the additional section.

       val-log-level: <number>
              Have  the  validator  print  validation  failures  to  the  log.
              Regardless  of the verbosity setting.  Default is 0, off.  At 1,
              for every user query that fails a line is printed to  the  logs.
              This  way  you  can monitor what happens with validation.  Use a
              diagnosis tool, such as dig or drill, to find out why validation
              is  failing  for  these  queries.  At 2, not only the query that
              failed is printed but also the reason why unbound thought it was
              wrong and which server sent the faulty data.

       val-permissive-mode: <yes or no>
              Instruct  the validator to mark bogus messages as indeterminate.
              The security checks are performed, but if the  result  is  bogus
              (failed  security),  the  reply  is not withheld from the client
              with SERVFAIL as usual. The client receives the bogus data.  For
              messages  that  are  found  to  be  secure  the AD bit is set in
              replies. Also logging is performed as for full validation.   The
              default value is "no".

       ignore-cd-flag: <yes or no>
              Instruct  unbound  to ignore the CD flag from clients and refuse
              to return bogus answers to them.  Thus, the  CD  (Checking  Dis-
              abled)  flag does not disable checking any more.  This is useful
              if legacy (w2008) servers that set the CD flag but cannot  vali-
              date  DNSSEC  themselves  are the clients, and then unbound pro-
              vides them with DNSSEC protection.  The default value is "no".

       serve-expired: <yes or no>
              If enabled, unbound attempts to serve old responses  from  cache
              with  a  TTL of 0 in the response without waiting for the actual
              resolution to finish.  The actual resolution answer ends  up  in
              the cache later on.  Default is "no".

       val-nsec3-keysize-iterations: <"list of values">
              List of keysize and iteration count values, separated by spaces,
              surrounded by quotes. Default is "1024 150 2048 500 4096  2500".
              This determines the maximum allowed NSEC3 iteration count before
              a message is simply marked insecure instead  of  performing  the
              many hashing iterations. The list must be in ascending order and
              have at least one entry. If you set it to "1024 65535" there  is
              no  restriction  to  NSEC3 iteration values.  This table must be
              kept short; a very long list could cause slower operation.

       add-holddown: <seconds>
              Instruct the auto-trust-anchor-file probe mechanism for  RFC5011
              autotrust  updates to add new trust anchors only after they have
              been visible for this time.  Default is 30 days as per the RFC.

       del-holddown: <seconds>
              Instruct the auto-trust-anchor-file probe mechanism for  RFC5011
              autotrust  updates  to  remove  revoked trust anchors after they
              have been kept in the revoked list for this long.  Default is 30
              days as per the RFC.

       keep-missing: <seconds>
              Instruct  the auto-trust-anchor-file probe mechanism for RFC5011
              autotrust updates to remove missing  trust  anchors  after  they
              have  been  unseen for this long.  This cleans up the state file
              if the target zone does not perform trust anchor revocation,  so
              this makes the auto probe mechanism work with zones that perform
              regular (non-5011) rollovers.  The default  is  366  days.   The
              value 0 does not remove missing anchors, as per the RFC.

       permit-small-holddown: <yes or no>
              Debug  option  that allows the autotrust 5011 rollover timers to
              assume very small values.  Default is no.

       key-cache-size: <number>
              Number of bytes size of the key cache. Default is  4  megabytes.
              A  plain  number  is  in bytes, append 'k', 'm' or 'g' for kilo-
              bytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).

       key-cache-slabs: <number>
              Number of slabs in the key cache. Slabs reduce  lock  contention
              by threads.  Must be set to a power of 2. Setting (close) to the
              number of cpus is a reasonable guess.

       neg-cache-size: <number>
              Number of bytes size of the aggressive negative  cache.  Default
              is  1  megabyte.  A plain number is in bytes, append 'k', 'm' or
              'g' for kilobytes, megabytes or gigabytes (1024*1024 bytes in  a
              megabyte).

       unblock-lan-zones: <yesno>
              Default  is  disabled.   If  enabled,  then  for private address
              space, the reverse lookups are no longer filtered.  This  allows
              unbound  when running as dns service on a host where it provides
              service for that host, to put out all of  the  queries  for  the
              'lan' upstream.  When enabled, only localhost, 127.0.0.1 reverse
              and ::1 reverse zones are configured with default  local  zones.
              Disable the option when unbound is running as a (DHCP-) DNS net-
              work resolver for a group of machines, where such lookups should
              be  filtered  (RFC  compliance),  this also stops potential data
              leakage about the local network to the upstream DNS servers.

       insecure-lan-zones: <yesno>
              Default is disabled.  If enabled, then reverse lookups  in  pri-
              vate  address space are not validated.  This is usually required
              whenever unblock-lan-zones is used.

       local-zone: <zone> <type>
              Configure a local zone. The type determines the answer  to  give
              if  there  is  no  match  from  local-data.  The types are deny,
              refuse, static, transparent, redirect, nodefault,  typetranspar-
              ent,  inform,  inform_deny,  always_transparent,  always_refuse,
              always_nxdomain, and are explained below. After that the default
              settings  are  listed.  Use  local-data:  to enter data into the
              local zone.  Answers  for  local  zones  are  authoritative  DNS
              answers. By default the zones are class IN.

              If you need more complicated authoritative data, with referrals,
              wildcards, CNAME/DNAME support, or DNSSEC authoritative service,
              setup  a  stub-zone  for it as detailed in the stub zone section
              below.

            deny Do not send an answer, drop the query.  If there is  a  match
                 from local data, the query is answered.

            refuse
                 Send an error message reply, with rcode REFUSED.  If there is
                 a match from local data, the query is answered.

            static
                 If there is a match from local data, the query  is  answered.
                 Otherwise,  the  query  is  answered with nodata or nxdomain.
                 For a negative answer a SOA is  included  in  the  answer  if
                 present as local-data for the zone apex domain.

            transparent
                 If  there  is a match from local data, the query is answered.
                 Otherwise if the query has a different  name,  the  query  is
                 resolved  normally.   If  the  query  is  for a name given in
                 localdata but no such type of data  is  given  in  localdata,
                 then  a  noerror nodata answer is returned.  If no local-zone
                 is given local-data causes a transparent zone to  be  created
                 by default.

            typetransparent
                 If  there  is a match from local data, the query is answered.
                 If the query is for a different name, or for  the  same  name
                 but  for  a  different  type, the query is resolved normally.
                 So, similar to transparent but types that are not  listed  in
                 local data are resolved normally, so if an A record is in the
                 local data that does  not  cause  a  nodata  reply  for  AAAA
                 queries.

            redirect
                 The  query is answered from the local data for the zone name.
                 There may be no local  data  beneath  the  zone  name.   This
                 answers  queries for the zone, and all subdomains of the zone
                 with the local data for the zone.  It can be used to redirect
                 a  domain  to  return  a  different address record to the end
                 user,   with   local-zone:   "example.com."   redirect    and
                 local-data:  "example.com. A 127.0.0.1" queries for www.exam-
                 ple.com and www.foo.example.com are redirected, so that users
                 with  web  browsers  cannot  access  sites  with suffix exam-
                 ple.com.

            inform
                 The query is answered normally,  same  as  transparent.   The
                 client  IP  address  (@portnumber) is printed to the logfile.
                 The log message is: timestamp,  unbound-pid,  info:  zonename
                 inform IP@port queryname type class.  This option can be used
                 for normal resolution, but machines looking up infected names
                 are logged, eg. to run antivirus on them.

            inform_deny
                 The query is dropped, like 'deny', and logged, like 'inform'.
                 Ie. find infected machines without answering the queries.

            always_transparent
                 Like transparent, but ignores local data  and  resolves  nor-
                 mally.

            always_refuse
                 Like refuse, but ignores local data and refuses the query.

            always_nxdomain
                 Like  static, but ignores local data and returns nxdomain for
                 the query.

            nodefault
                 Used to turn off default contents for AS112 zones. The  other
                 types also turn off default contents for the zone. The 'node-
                 fault' option has no other effect than  turning  off  default
                 contents  for  the  given  zone.   Use  nodefault  if you use
                 exactly that zone, if you want to use a subzone,  use  trans-
                 parent.

       The  default  zones are localhost, reverse 127.0.0.1 and ::1, the onion
       and the AS112 zones. The AS112 zones are reverse DNS zones for  private
       use  and  reserved  IP  addresses for which the servers on the internet
       cannot provide correct answers. They are configured by default to  give
       nxdomain  (no  reverse information) answers. The defaults can be turned
       off by specifying your own local-zone of that name, or using the 'node-
       fault' type. Below is a list of the default zone contents.

            localhost
                 The  IP4  and  IP6 localhost information is given. NS and SOA
                 records are provided for completeness and to satisfy some DNS
                 update tools. Default content:
                 local-zone: "localhost." static
                 local-data: "localhost. 10800 IN NS localhost."
                 local-data: "localhost. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "localhost. 10800 IN A 127.0.0.1"
                 local-data: "localhost. 10800 IN AAAA ::1"

            reverse IPv4 loopback
                 Default content:
                 local-zone: "127.in-addr.arpa." static
                 local-data: "127.in-addr.arpa. 10800 IN NS localhost."
                 local-data: "127.in-addr.arpa. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "1.0.0.127.in-addr.arpa. 10800 IN
                     PTR localhost."

            reverse IPv6 loopback
                 Default content:
                 local-zone: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa." static
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     NS localhost."
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     PTR localhost."

            onion (RFC 7686)
                 Default content:
                 local-zone: "onion." static
                 local-data: "onion. 10800 IN NS localhost."
                 local-data: "onion. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

            reverse RFC1918 local use zones
                 Reverse  data  for zones 10.in-addr.arpa, 16.172.in-addr.arpa
                 to    31.172.in-addr.arpa,     168.192.in-addr.arpa.      The
                 local-zone:  is  set  static  and  as  local-data: SOA and NS
                 records are provided.

            reverse RFC3330 IP4 this, link-local, testnet and broadcast
                 Reverse data for zones 0.in-addr.arpa,  254.169.in-addr.arpa,
                 2.0.192.in-addr.arpa  (TEST  NET  1), 100.51.198.in-addr.arpa
                 (TEST  NET   2),   113.0.203.in-addr.arpa   (TEST   NET   3),
                 255.255.255.255.in-addr.arpa.   And  from 64.100.in-addr.arpa
                 to 127.100.in-addr.arpa (Shared Address Space).

            reverse RFC4291 IP6 unspecified
                 Reverse data for zone
                 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.

            reverse RFC4193 IPv6 Locally Assigned Local Addresses
                 Reverse data for zone D.F.ip6.arpa.

            reverse RFC4291 IPv6 Link Local Addresses
                 Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.

            reverse IPv6 Example Prefix
                 Reverse data for zone 8.B.D.0.1.0.0.2.ip6.arpa. This zone  is
                 used  for tutorials and examples. You can remove the block on
                 this zone with:
                   local-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
                 You can also selectively unblock a part of the zone by making
                 that part transparent with a local-zone statement.  This also
                 works with the other default zones.

       local-data: "<resource record string>"
            Configure local data, which is served in reply to queries for  it.
            The query has to match exactly unless you configure the local-zone
            as redirect. If not matched exactly, the  local-zone  type  deter-
            mines  further processing. If local-data is configured that is not
            a subdomain of a local-zone, a transparent local-zone  is  config-
            ured.   For  record  types  such  as TXT, use single quotes, as in
            local-data: 'example. TXT "text"'.

            If you need more complicated authoritative data,  with  referrals,
            wildcards,  CNAME/DNAME  support, or DNSSEC authoritative service,
            setup a stub-zone for it as detailed  in  the  stub  zone  section
            below.

       local-data-ptr: "IPaddr name"
            Configure  local data shorthand for a PTR record with the reversed
            IPv4 or IPv6 address and the host name.   For  example  "192.0.2.4
            www.example.com".   TTL  can  be  inserted like this: "2001:DB8::4
            7200 www.example.com"

       local-zone-tag: <zone> <"list of tags">
            Assign tags to localzones. Tagged localzones will only be  applied
            when the used access-control element has a matching tag. Tags must
            be defined in define-tags.  Enclose list of tags  in  quotes  ("")
            and put spaces between tags.

       local-zone-override: <zone> <IP netblock> <type>
            Override  the  localzone  type for queries from addresses matching
            netblock.  Use this localzone type, regardless the type configured
            for  the  local-zone (both tagged and untagged) and regardless the
            type configured using access-control-tag-action.

       ratelimit: <number or 0>
            Enable ratelimiting of queries sent to nameserver  for  performing
            recursion.   If  0,  the  default, it is disabled.  This option is
            experimental at this time.  The ratelimit is in queries per second
            that  are  allowed.   More  queries  are turned away with an error
            (servfail).  This stops recursive floods, eg. random query  names,
            but not spoofed reflection floods.  Cached responses are not rate-
            limited by this setting.  The zone of the query is  determined  by
            examining  the  nameservers  for it, the zone name is used to keep
            track of the rate.  For example, 1000 may be a suitable  value  to
            stop the server from being overloaded with random names, and keeps
            unbound from sending traffic to the nameservers for those zones.

       ratelimit-size: <memory size>
            Give the size of the data structure in which the  current  ongoing
            rates  are  kept  track in.  Default 4m.  In bytes or use m(mega),
            k(kilo), g(giga).  The ratelimit structure is small, so this  data
            structure likely does not need to be large.

       ratelimit-slabs: <number>
            Give  power of 2 number of slabs, this is used to reduce lock con-
            tention in the ratelimit tracking data structure.   Close  to  the
            number of cpus is a fairly good setting.

       ratelimit-factor: <number>
            Set  the  amount  of  queries  to  rate  limit  when  the limit is
            exceeded.  If set to 0, all queries are dropped for domains  where
            the  limit is exceeded.  If set to another value, 1 in that number
            is allowed through to complete.   Default  is  10,  allowing  1/10
            traffic to flow normally.  This can make ordinary queries complete
            (if repeatedly queried for), and enter the cache, whilst also mit-
            igating the traffic flow by the factor given.

       ratelimit-for-domain: <domain> <number qps>
            Override  the global ratelimit for an exact match domain name with
            the listed number.  You can give this for  any  number  of  names.
            For  example, for a top-level-domain you may want to have a higher
            limit than other names.

       ratelimit-below-domain: <domain> <number qps>
            Override the global ratelimit for a domain name that ends in  this
            name.  You can give this multiple times, it then describes differ-
            ent settings in different parts of  the  namespace.   The  closest
            matching  suffix is used to determine the qps limit.  The rate for
            the  exact  matching  domain  name  is  not  changed,  use   rate-
            limit-for-domain to set that, you might want to use different set-
            tings for a top-level-domain and subdomains.

       ip-ratelimit: <number or 0>
            Enable global ratelimiting of queries accepted per ip address.  If
            0,  the  default,  it is disabled.  This option is experimental at
            this time.  The ratelimit  is  in  queries  per  second  that  are
            allowed.  More queries are completely dropped and will not receive
            a reply, SERVFAIL or otherwise.  IP  ratelimiting  happens  before
            looking in the cache. This may be useful for mitigating amplifica-
            tion attacks.

       ip-ratelimit-size: <memory size>
            Give the size of the data structure in which the  current  ongoing
            rates  are  kept  track in.  Default 4m.  In bytes or use m(mega),
            k(kilo), g(giga).  The ip ratelimit structure is  small,  so  this
            data structure likely does not need to be large.

       ip-ratelimit-slabs: <number>
            Give  power of 2 number of slabs, this is used to reduce lock con-
            tention in the ip ratelimit tracking data structure.  Close to the
            number of cpus is a fairly good setting.

       ip-ratelimit-factor: <number>
            Set  the  amount  of  queries  to  rate  limit  when  the limit is
            exceeded.  If set to 0, all  queries  are  dropped  for  addresses
            where  the  limit is exceeded.  If set to another value, 1 in that
            number is allowed through to complete.  Default  is  10,  allowing
            1/10  traffic  to  flow  normally.  This can make ordinary queries
            complete (if repeatedly queried for), and enter the cache,  whilst
            also mitigating the traffic flow by the factor given.

   Remote Control Options
       In  the remote-control: clause are the declarations for the remote con-
       trol facility.  If this is enabled, the unbound-control(8) utility  can
       be  used  to  send  commands to the running unbound server.  The server
       uses these clauses to setup SSLv3 / TLSv1 security for the  connection.
       The  unbound-control(8)  utility  also reads the remote-control section
       for options.  To setup the correct  self-signed  certificates  use  the
       unbound-control-setup(8) utility.

       control-enable: <yes or no>
            The  option is used to enable remote control, default is "no".  If
            turned off, the server does not listen for control commands.

       control-interface: <ip address or path>
            Give IPv4 or IPv6 addresses or local socket path to listen on  for
            control  commands.   By  default  localhost (127.0.0.1 and ::1) is
            listened to.  Use 0.0.0.0 and ::0 to listen to all interfaces.  If
            you  change  this  and  permissions  have  been  dropped, you must
            restart the server for the change to take effect.

       control-port: <port number>
            The port number to listen on for IPv4 or IPv6 control  interfaces,
            default  is  8953.   If  you change this and permissions have been
            dropped, you must restart  the  server  for  the  change  to  take
            effect.

       control-use-cert: <yes or no>
            Whether  to  require certificate authentication of control connec-
            tions.  The default is "yes".  This should not be  changed  unless
            there  are  other  mechanisms  in place to prevent untrusted users
            from accessing the remote control interface.

       server-key-file: <private key file>
            Path to the server private  key,  by  default  unbound_server.key.
            This file is generated by the unbound-control-setup utility.  This
            file is used by the unbound server, but not by unbound-control.

       server-cert-file: <certificate file.pem>
            Path  to  the  server  self   signed   certificate,   by   default
            unbound_server.pem.   This  file  is generated by the unbound-con-
            trol-setup utility.  This file is used by the unbound server,  and
            also by unbound-control.

       control-key-file: <private key file>
            Path  to  the  control client private key, by default unbound_con-
            trol.key.  This file is  generated  by  the  unbound-control-setup
            utility.  This file is used by unbound-control.

       control-cert-file: <certificate file.pem>
            Path  to  the  control client certificate, by default unbound_con-
            trol.pem.  This certificate has to be signed with the server  cer-
            tificate.   This  file  is  generated by the unbound-control-setup
            utility.  This file is used by unbound-control.

   Stub Zone Options
       There may be multiple stub-zone: clauses. Each with a name: and zero or
       more  hostnames  or IP addresses.  For the stub zone this list of name-
       servers is used. Class IN is assumed.  The servers should be  authority
       servers,  not  recursors;  unbound  performs  the  recursive processing
       itself for stub zones.

       The stub zone can be used to configure authoritative data to be used by
       the resolver that cannot be accessed using the public internet servers.
       This is useful for  company-local  data  or  private  zones.  Setup  an
       authoritative  server  on a different host (or different port). Enter a
       config entry for unbound with stub-addr: <ip address  of  host[@port]>.
       The unbound resolver can then access the data, without referring to the
       public internet for it.

       This setup allows DNSSEC signed zones to be served by  that  authorita-
       tive  server, in which case a trusted key entry with the public key can
       be put in config, so that unbound can validate the data and set the  AD
       bit  on  replies for the private zone (authoritative servers do not set
       the AD bit).  This setup makes unbound capable of answering queries for
       the private zone, and can even set the AD bit ('authentic'), but the AA
       ('authoritative') bit is not set on these replies.

       Consider  adding  server:  statements  for  domain-insecure:  and   for
       local-zone: name nodefault for the zone if it is a locally served zone.
       The insecure clause stops DNSSEC from invalidating the zone.  The local
       zone nodefault (or transparent) clause makes the (reverse-) zone bypass
       unbound's filtering of RFC1918 zones.

       name: <domain name>
              Name of the stub zone.

       stub-host: <domain name>
              Name of stub zone nameserver. Is itself resolved  before  it  is
              used.

       stub-addr: <IP address>
              IP address of stub zone nameserver. Can be IP 4 or IP 6.  To use
              a nondefault port for DNS communication append '@' with the port
              number.

       stub-prime: <yes or no>
              This  option  is  by default off.  If enabled it performs NS set
              priming, which is similar to root hints, where it  starts  using
              the  list of nameservers currently published by the zone.  Thus,
              if the hint list is slightly outdated, the resolver picks  up  a
              correct list online.

       stub-first: <yes or no>
              If  enabled,  a query is attempted without the stub clause if it
              fails.  The data could not be retrieved and  would  have  caused
              SERVFAIL  because  the  servers  are  unreachable, instead it is
              tried without this clause.  The default is no.

       stub-ssl-upstream: <yes or no>
              Enabled or disable whether the queries to this stub use SSL  for
              transport.  Default is no.

   Forward Zone Options
       There may be multiple forward-zone: clauses. Each with a name: and zero
       or more hostnames or IP addresses.  For the forward zone this  list  of
       nameservers  is  used  to forward the queries to. The servers listed as
       forward-host: and forward-addr: have to handle  further  recursion  for
       the  query.   Thus,  those  servers  are not authority servers, but are
       (just like unbound is) recursive servers too; unbound does not  perform
       recursion itself for the forward zone, it lets the remote server do it.
       Class IN is assumed.  A forward-zone entry with name  "."  and  a  for-
       ward-addr  target will forward all queries to that other server (unless
       it can answer from the cache).

       name: <domain name>
              Name of the forward zone.

       forward-host: <domain name>
              Name of server to forward to. Is itself resolved  before  it  is
              used.

       forward-addr: <IP address>
              IP address of server to forward to. Can be IP 4 or IP 6.  To use
              a nondefault port for DNS communication append '@' with the port
              number.

       forward-first: <yes or no>
              If  enabled,  a query is attempted without the forward clause if
              it fails.  The data could not be retrieved and would have caused
              SERVFAIL  because  the  servers  are  unreachable, instead it is
              tried without this clause.  The default is no.

       forward-ssl-upstream: <yes or no>
              Enabled or disable whether the queries to this forwarder use SSL
              for transport.  Default is no.

   View Options
       There may be multiple view: clauses. Each with a name: and zero or more
       local-zone and local-data elements. View can be mapped to  requests  by
       specifying  the  view  name  in an access-control-view element. Options
       from matching views will override global options. Global  options  will
       be used if no matching view is found.

       name: <view name>
              Name  of  the  view.  Must  be  unique.  This  name  is  used in
              access-control-view elements.

       local-zone: <zone> <type>
              View specific local-zone elements. Has the same types and behav-
              iour as the global local-zone elements.

       local-data: "<resource record string>"
              View specific local-data elements. Has the same behaviour as the
              global local-data elements.

       local-data-ptr: "IPaddr name"
              View specific local-data-ptr elements. Has the same behaviour as
              the global local-data-ptr elements.

       view-first: <yes or no>
              If  enabled,  it  attempts  to  use  the  global  local-zone and
              local-data if there is no match in the  view  specific  options.
              The default is no.

   Python Module Options
       The  python: clause gives the settings for the python(1) script module.
       This module acts like the iterator and validator modules do, on queries
       and  answers.   To  enable the script module it has to be compiled into
       the daemon, and the word "python" has to be put in  the  module-config:
       option (usually first, or between the validator and iterator).

       If the chroot: option is enabled, you should make sure Python's library
       directory structure is bind mounted in the new  root  environment,  see
       mount(8).  Also the python-script: path should be specified as an abso-
       lute path relative to the new root, or as a relative path to the  work-
       ing directory.

       python-script: <python file>
              The script file to load.

   DNS64 Module Options
       The  dns64  module must be configured in the module-config: "dns64 val-
       idator iterator" directive and  be  compiled  into  the  daemon  to  be
       enabled.  These settings go in the server: section.

       dns64-prefix: <IPv6 prefix>
              This  sets  the  DNS64  prefix to use to synthesize AAAA records
              with.  It must  be  /96  or  shorter.   The  default  prefix  is
              64:ff9b::/96.

       dns64-synthall: <yes or no>
              Debug  option,  default  no.   If  enabled,  synthesize all AAAA
              records despite the presence of actual AAAA records.

   DNSCrypt Options
       The dnscrypt: clause give the settings of the dnscrypt  channel.  While
       those  options  are  available, they are only meaningful if unbound was
       compiled with --enable-dnscrypt.  Currently certificate and secret/pub-
       lic  keys cannot be generated by unbound.  You can use dnscrypt-wrapper
       to generate those:  https://github.com/cofyc/dnscrypt-wrapper/blob/mas-
       ter/README.md#usage

       dnscrypt-enable: <yes or no>
              Whether  or  not  the dnscrypt config should be enabled. You may
              define configuration but not activate it.  The default is no.

       dnscrypt-port: <port number>
              On which port should dnscrypt should be activated. Note that you
              should  have  a  matching interface option defined in the server
              section for this port.

       dnscrypt-provider: <provider name>
              The provider name to use to distribute certificates. This is  of
              the form: 2.dnscrypt-cert.example.com.. The name MUST end with a
              dot.

       dnscrypt-secret-key: <path to secret key file>
              Path to the time limited secret key file.  This  option  may  be
              specified multiple times.

       dnscrypt-provider-cert: <path to cert file>
              Path  to  the  certificate  related to the dnscrypt-secret-keys.
              This option may be specified multiple times.

   EDNS Client Subnet Module Options
       The ECS module must be configured in  the  module-config:  "subnetcache
       validator  iterator"  directive  and  be compiled into the daemon to be
       enabled.  These settings go in the server: section.

       If the destination address is whitelisted with  Unbound  will  add  the
       EDNS0  option to the query containing the relevant part of the client's
       address. When an answer contains the ECS option the  response  and  the
       option are placed in a specialized cache. If the authority indicated no
       support, the response is stored in the regular cache.

       Additionally, when a client includes the option in its queries, Unbound
       will  forward the option to the authority regardless of the authorities
       presence in the whitelist. In this case the lookup in the regular cache
       is skipped.

       The  maximum size of the ECS cache is controlled by 'msg-cache-size' in
       the configuration file. On top of that, for each query only 100 differ-
       ent subnets are allowed to be stored for each address family. Exceeding
       that number, older entries will be purged from cache.

       send-client-subnet: <IP address>
              Send client source address to this  authority.  Append  /num  to
              indicate  a  classless  delegation  netblock,  for  example like
              10.2.3.4/24 or 2001::11/64. Can be given multiple times. Author-
              ities not listed will not receive edns-subnet information.

       client-subnet-always-forward: <yes or no>
              Specify  whether  the  ECS  whitelist  check  (configured  using
              send-client-subnet) is applied for  all  queries,  even  if  the
              triggering query contains an ECS record, or only for queries for
              which the ECS record is generated using the querier address (and
              therefore  did  not  contain  ECS  data in the client query). If
              enabled, the whitelist check is skipped when  the  client  query
              contains an ECS record. Default is no.

       max-client-subnet-ipv6: <number>
              Specifies the maximum prefix length of the client source address
              we are willing to expose to third parties for IPv6.  Defaults to
              56.

       max-client-subnet-ipv4: <number>
              Specifies the maximum prefix length of the client source address
              we are willing to expose to third parties for IPv4. Defaults  to
              24.

MEMORY CONTROL EXAMPLE
       In the example config settings below memory usage is reduced. Some ser-
       vice levels are lower, notable very large data and a high TCP load  are
       no longer supported. Very large data and high TCP loads are exceptional
       for the DNS.  DNSSEC validation is enabled, just add trust anchors.  If
       you do not have to worry about programs using more than 3 Mb of memory,
       the below example is not for you. Use the defaults to receive full ser-
       vice, which on BSD-32bit tops out at 30-40 Mb after heavy usage.

       # example settings that reduce memory usage
       server:
            num-threads: 1
            outgoing-num-tcp: 1 # this limits TCP service, uses less buffers.
            incoming-num-tcp: 1
            outgoing-range: 60  # uses less memory, but less performance.
            msg-buffer-size: 8192   # note this limits service, 'no huge stuff'.
            msg-cache-size: 100k
            msg-cache-slabs: 1
            rrset-cache-size: 100k
            rrset-cache-slabs: 1
            infra-cache-numhosts: 200
            infra-cache-slabs: 1
            key-cache-size: 100k
            key-cache-slabs: 1
            neg-cache-size: 10k
            num-queries-per-thread: 30
            target-fetch-policy: "2 1 0 0 0 0"
            harden-large-queries: "yes"
            harden-short-bufsize: "yes"

FILES
       /usr/local/etc/unbound
              default unbound working directory.

       /usr/local/etc/unbound
              default chroot(2) location.

       /usr/local/etc/unbound/unbound.conf
              unbound configuration file.

       /usr/local/etc/unbound/unbound.pid
              default unbound pidfile with process ID of the running daemon.

       unbound.log
              unbound log file. default is to log to syslog(3).

SEE ALSO
       unbound(8), unbound-checkconf(8).

AUTHORS
       Unbound  was written by NLnet Labs. Please see CREDITS file in the dis-
       tribution for further details.



NLnet Labs                       Apr 24, 2017                  unbound.conf(5)