Provided by: unbound_1.4.16-1_i386 bug

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
       anywhere, and takes a  single  filename  as  an  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.

   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
              commandline, 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
              statistics. Default is no.

       extended-statistics: <yes or no>
              If   enabled,   extended    statistics    are    printed    from
              unbound-control(8).   Default  is  off, because keeping track of
              more  statistics  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
              localhost.   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
              specified the default port (from port) is used.

       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>
              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
              interfaces. If none are given the default (all) is used. You can
              specify    the    same    interfaces    in    interface:     and
              outgoing-interface: lines, the interfaces are then used for both
              purposes. Outgoing  queries  are  sent  via  a  random  outgoing
              interface to counter spoofing.

       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
              compile  options.  Larger  numbers need extra resources from the
              operating system.  For performance a 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
              permitted ports and subtracting the avoided ports from  the  set
              of  allowed  ports.   The  processing  starts  with the non IANA
              allocated 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.

       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.

       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  lower  than  that  value.
              Default   is  4096  which  is  RFC  recommended.   If  you  have
              fragmentation 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).

       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
              contention 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
              simultaneously.  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
              (numqueriesperthread / 2) / (average time for such long queries)
              qps.     The    qps    for    short   queries   can   be   about
              (numqueriesperthread / 2) / (jostletimeout in whole seconds) qps
              per thread, about (1024/2)*5 = 2560 qps by default.

       so-rcvbuf: <number>
              If  not  0,  then  set  the  SO_RCVBUF socket option to get more
              buffer 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
              buffer  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
              system 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.

       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
              kilobytes,   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 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.

       infra-host-ttl: <seconds>
              Time to live for entries in  the  host  cache.  The  host  cache
              contains   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.

       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.

       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-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
              private  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
              443, only interfaces configured with that port number as @number
              get the SSL service.

       do-daemonize: <yes or no>
              Enable or disable whether the  unbound  server  forks  into  the
              background as a daemon. 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 or allow_snoop.

              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
              operations  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
              policy,  and dropping may result in (possibly excessive) retried
              queries.

       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
              portion.

              The  pidfile  can  be  either  a  relative  path  to the working
              directory, 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
              "/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
              "/etc/unbound".

       logfile: <filename>
              If ""  is  given,  logging  goes  to  stderr,  or  nowhere  once
              daemonized.   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
              syslog(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-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
              (significantly)  slower.  Odd (nonprintable) characters in names
              are printed as '?'.

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

       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
              numbers.  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  draft-vixie-dnsext-resimprove, returns nxdomain to queries
              for a name below another  name  that  is  already  known  to  be
              nxdomain.  DNSSEC mandates 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.

       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
              validation  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
              target-fetch-policy  to  increase  the max depth that is checked
              to.

       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.

       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  occurence  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
              additional 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
              spamblocklists as they use that.

       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.

       module-config: <"module names">
              Module configuration,  a  list  of  module  names  separated  by
              spaces, 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.

       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
              addition 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>
              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-anchor: <"Resource Record">
              Much like trust-anchor, this is a DLV  anchor  with  the  DS  or
              DNSKEY inline.

       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
              verifying  RRSIG  inception and expiration dates, instead of the
              current date. Do not set this unless you are debugging signature
              inception   and  expiration.  The  value  -1  ignores  the  date
              altogether, 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
              (expiration -  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 signatures.

       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
              (expiration  -  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
              section  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
              protentially 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
              Disabled) flag does not disable  checking  any  more.   This  is
              useful if legacy (w2008) servers that set the CD flag but cannot
              validate DNSSEC themselves are the  clients,  and  then  unbound
              provides  them  with  DNSSEC  protection.   The default value 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.

       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
              kilobytes,  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).

       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,
              typetransparent, 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.example.com  and  www.foo.example.com  are redirected, so
                 that users with web browsers cannot access sites with  suffix
                 example.com.

            nodefault
                 Used  to turn off default contents for AS112 zones. The other
                 types also turn  off  default  contents  for  the  zone.  The
                 'nodefault'  option  has  no  other  effect  than turning off
                 default contents for the given zone.

       The default zones are localhost, reverse 127.0.0.1  and  ::1,  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
       'nodefault' 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."

            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.

            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
            determines further processing. If local-data is configured that is
            not a subdomain of  a  local-zone,  a  transparent  local-zone  is
            configured.   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"

   Remote Control Options
       In the remote-control: clause  are  the  declarations  for  the  remote
       control  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 "yes".  If
            turned off, the server does not listen for control commands.

       control-interface: <ip address>
            Give IPv4 or IPv6 addresses 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.

       control-port: <port number>
            The  port  number  to  listen  on for control commands, default is
            8953.  If you change this port number, and permissions  have  been
            dropped,  a  reload  is not sufficient to open the port again, you
            must then restart.

       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-control-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_control.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_control.pem.   This  certificate has to be signed with the
            server   certificate.    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
       nameservers 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
       authoritative 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.

       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.

   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
       forward-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.

   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).

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

MEMORY CONTROL EXAMPLE

       In the example config settings below  memory  usage  is  reduced.  Some
       service  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 service, 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

       /etc/unbound
              default unbound working directory.

       /etc/unbound
              default chroot(2) location.

       /etc/unbound/unbound.conf
              unbound configuration file.

       /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
       distribution for further details.