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       dnsmasq - A lightweight DHCP and caching DNS server.


       dnsmasq [OPTION]...


       dnsmasq  is  a lightweight DNS, TFTP and DHCP server. It is intended to
       provide coupled DNS and DHCP service to a LAN.

       Dnsmasq accepts DNS queries and  either  answers  them  from  a  small,
       local,  cache  or  forwards  them  to a real, recursive, DNS server. It
       loads the contents of /etc/hosts so that local hostnames which  do  not
       appear  in  the global DNS can be resolved and also answers DNS queries
       for DHCP configured hosts.

       The  dnsmasq  DHCP  server  supports  static  address  assignments  and
       multiple  networks.  It  automatically  sends a sensible default set of
       DHCP options, and can be configured to send any  desired  set  of  DHCP
       options,  including  vendor-encapsulated options. It includes a secure,
       read-only, TFTP server to allow net/PXE boot of  DHCP  hosts  and  also
       supports BOOTP.

       Dnsmasq supports IPv6 for DNS, but not DHCP.


       Note  that  in  general  missing  parameters are allowed and switch off
       functions, for instance "--pid-file" disables writing a  PID  file.  On
       BSD,  unless  the  GNU  getopt  library is linked, the long form of the
       options does not work on the command line; it is  still  recognised  in
       the configuration file.

       --test Read and syntax check configuration file(s). Exit with code 0 if
              all is OK, or  a  non-zero  code  otherwise.  Do  not  start  up

       -h, --no-hosts
              Don’t read the hostnames in /etc/hosts.

       -H, --addn-hosts=<file>
              Additional  hosts  file.  Read  the  specified  file  as well as
              /etc/hosts. If -h is given, read only the specified  file.  This
              option  may be repeated for more than one additional hosts file.
              If a directory is given, then read all the  files  contained  in
              that directory.

       -E, --expand-hosts
              Add  the domain to simple names (without a period) in /etc/hosts
              in the same way as for DHCP-derived names. Note that  this  does
              not  apply  to  domain names in cnames, PTR records, TXT records

       -T, --local-ttl=<time>
              When replying with  information  from  /etc/hosts  or  the  DHCP
              leases  file  dnsmasq  by default sets the time-to-live field to
              zero, meaning that the requestor should  not  itself  cache  the
              information.  This  is  the  correct  thing  to do in almost all
              situations. This option allows a time-to-live (in seconds) to be
              given for these replies. This will reduce the load on the server
              at  the  expense  of  clients  using  stale  data   under   some

              Negative replies from upstream servers normally contain time-to-
              live information in SOA records which dnsmasq uses for  caching.
              If  the  replies  from  upstream  servers omit this information,
              dnsmasq does not cache the reply. This option  gives  a  default
              value  for time-to-live (in seconds) which dnsmasq uses to cache
              negative replies even in the absence of an SOA record.

              Set a maximum TTL value that will be handed out to clients.  The
              specified  maximum  TTL  will be given to clients instead of the
              true TTL value if it is lower. The true  TTL  value  is  however
              kept in the cache to avoid flooding the upstream DNS servers.

       -k, --keep-in-foreground
              Do  not  go  into the background at startup but otherwise run as
              normal. This is intended for  use  when  dnsmasq  is  run  under
              daemontools or launchd.

       -d, --no-daemon
              Debug  mode:  don’t  fork  to  the background, don’t write a pid
              file, don’t change user id, generate a complete  cache  dump  on
              receipt  on SIGUSR1, log to stderr as well as syslog, don’t fork
              new processes to handle TCP queries.

       -q, --log-queries
              Log the results of DNS queries handled by dnsmasq. Enable a full
              cache dump on receipt of SIGUSR1.

       -8, --log-facility=<facility>
              Set the facility to which dnsmasq will send syslog entries, this
              defaults to  DAEMON,  and  to  LOCAL0  when  debug  mode  is  in
              operation.  If  the  facility  given  contains  at least one ’/’
              character, it is taken to be a filename, and dnsmasq logs to the
              given  file,  instead  of  syslog.  If  the facility is ’-’ then
              dnsmasq logs to stderr.  (Errors  whilst  reading  configuration
              will  still  go  to  syslog,  but  all  output from a successful
              startup, and all output whilst running, will go  exclusively  to
              the file.) When logging to a file, dnsmasq will close and reopen
              the file when it receives SIGUSR2. This allows the log  file  to
              be rotated without stopping dnsmasq.

              Enable  asynchronous logging and optionally set the limit on the
              number of lines which will be queued by dnsmasq when writing  to
              the syslog is slow.  Dnsmasq can log asynchronously: this allows
              it to continue functioning without being blocked by syslog,  and
              allows  syslog  to  use  dnsmasq for DNS queries without risking
              deadlock.  If the queue of log-lines becomes full, dnsmasq  will
              log  the overflow, and the number of messages  lost. The default
              queue length is 5, a sane value would be  5-25,  and  a  maximum
              limit of 100 is imposed.

       -x, --pid-file=<path>
              Specify  an  alternate path for dnsmasq to record its process-id
              in. Normally /var/run/

       -u, --user=<username>
              Specify the userid to which dnsmasq will change  after  startup.
              Dnsmasq  must normally be started as root, but it will drop root
              privileges  after  startup  by  changing  id  to  another  user.
              Normally  this user is "nobody" but that can be over-ridden with
              this switch.

       -g, --group=<groupname>
              Specify the group which dnsmasq will run  as.  The  defaults  to
              "dip",     if     available,    to    facilitate    access    to
              /etc/ppp/resolv.conf which is not normally world readable.

       -v, --version
              Print the version number.

       -p, --port=<port>
              Listen on <port> instead of the standard DNS port (53).  Setting
              this to zero completely disables DNS function, leaving only DHCP
              and/or TFTP.

       -P, --edns-packet-max=<size>
              Specify the largest EDNS.0 UDP packet which is supported by  the
              DNS    forwarder.    Defaults    to    4096,    which   is   the
              RFC5625-recommended size.

       -Q, --query-port=<query_port>
              Send outbound DNS queries from, and listen for their replies on,
              the  specific  UDP  port  <query_port>  instead  of using random
              ports. NOTE that using this option will make dnsmasq less secure
              against  DNS  spoofing attacks but it may be faster and use less
              resources.  Setting this option to  zero  makes  dnsmasq  use  a
              single  port  allocated  to  it  by the OS: this was the default
              behaviour in versions prior to 2.43.

              Do not use ports less than that given as source for outbound DNS
              queries.  Dnsmasq  picks  random  ports  as  source for outbound
              queries: when this option is given, the ports used  will  always
              to  larger  than  that  specified.  Useful  for  systems  behind

       -i, --interface=<interface name>
              Listen only on the specified interface(s). Dnsmasq automatically
              adds the loopback (local) interface to the list of interfaces to
              use when the --interface option  is used. If no  --interface  or
              --listen-address  options  are  given  dnsmasq  listens  on  all
              available interfaces  except  any  given  in  --except-interface
              options.  IP  alias interfaces (eg "eth1:0") cannot be used with
              --interface or --except-interface options, use  --listen-address

       -I, --except-interface=<interface name>
              Do not listen on the specified interface. Note that the order of
              --listen-address --interface and --except-interface options does
              not  matter  and that --except-interface options always override
              the others.

       -2, --no-dhcp-interface=<interface name>
              Do not provide DHCP or TFTP on the specified interface,  but  do
              provide DNS service.

       -a, --listen-address=<ipaddr>
              Listen  on  the  given  IP  address(es).  Both  --interface  and
              --listen-address options may be given, in which case the set  of
              both   interfaces  and  addresses  is  used.  Note  that  if  no
              --interface option is given, but  --listen-address  is,  dnsmasq
              will  not  automatically  listen  on  the loopback interface. To
              achieve this, its IP  address,,  must  be  explicitly
              given as a --listen-address option.

       -z, --bind-interfaces
              On systems which support it, dnsmasq binds the wildcard address,
              even when it is listening  on  only  some  interfaces.  It  then
              discards  requests  that  it  shouldn’t  reply  to. This has the
              advantage of working even when interfaces come and go and change
              address.  This  option  forces  dnsmasq  to really bind only the
              interfaces it is listening on. About the only time when this  is
              useful  is  when running another nameserver (or another instance
              of dnsmasq) on  the  same  machine.  Setting  this  option  also
              enables multiple instances of dnsmasq which provide DHCP service
              to run in the same machine.

       -y, --localise-queries
              Return answers to DNS queries from /etc/hosts  which  depend  on
              the  interface  over  which the query was received. If a name in
              /etc/hosts has more than one address associated with it, and  at
              least  one  of  those  addresses  is  on  the same subnet as the
              interface to which the query was  sent,  then  return  only  the
              address(es)  on  that  subnet. This allows for a server  to have
              multiple addresses in /etc/hosts corresponding to  each  of  its
              interfaces,  and  hosts  will  get  the correct address based on
              which network they are attached to. Currently this  facility  is
              limited to IPv4.

       -b, --bogus-priv
              Bogus  private  reverse lookups. All reverse lookups for private
              IP  ranges  (ie  192.168.x.x,  etc)  which  are  not  found   in
              /etc/hosts  or  the  DHCP leases file are answered with "no such
              domain" rather than being forwarded upstream.

       -V, --alias=[<old-ip>]|[<start-ip>-<end-ip>],<new-ip>[,<mask>]
              Modify IPv4 addresses returned from upstream nameservers; old-ip
              is  replaced  by  new-ip. If the optional mask is given then any
              address which matches the masked old-ip will be re-written.  So,
              for   instance  --alias=,,  will  map
     to and  to  This  is  what
              Cisco  PIX  routers call "DNS doctoring". If the old IP is given
              as range, then only addresses in the range, rather than a  whole
              subnet,              are              re-written.             So
              --alias=,,    maps
    > to>

       -B, --bogus-nxdomain=<ipaddr>
              Transform  replies  which  contain the IP address given into "No
              such domain" replies. This is intended to counteract  a  devious
              move  made  by  Verisign  in  September  2003  when they started
              returning the address of an advertising web page in response  to
              queries  for unregistered names, instead of the correct NXDOMAIN
              response. This option tells dnsmasq to fake the correct response
              when  it  sees  this  behaviour.  As at Sept 2003 the IP address
              being returned by Verisign is

       -f, --filterwin2k
              Later versions of windows make periodic DNS requests which don’t
              get  sensible answers from the public DNS and can cause problems
              by triggering dial-on-demand links. This flag turns on an option
              to filter such requests. The requests blocked are for records of
              types SOA and SRV, and type ANY where  the  requested  name  has
              underscores, to catch LDAP requests.

       -r, --resolv-file=<file>
              Read  the  IP addresses of the upstream nameservers from <file>,
              instead of /etc/resolv.conf. For the format  of  this  file  see
              resolv.conf(5) the only lines relevant to dnsmasq are nameserver
              ones. Dnsmasq can be told to  poll  more  than  one  resolv.conf
              file,  the  first  file  name   specified overrides the default,
              subsequent ones add to the  list.  This  is  only  allowed  when
              polling; the file with the currently latest modification time is
              the one used.

       -R, --no-resolv
              Don’t read /etc/resolv.conf. Get upstream servers only from  the
              command line or the dnsmasq configuration file.

       -1, --enable-dbus
              Allow dnsmasq configuration to be updated via DBus method calls.
              The configuration which can be changed is upstream  DNS  servers
              (and  corresponding  domains)  and  cache  clear.  Requires that
              dnsmasq has been built with DBus support.

       -o, --strict-order
              By default, dnsmasq will send queries to  any  of  the  upstream
              servers  it  knows  about  and  tries to favour servers that are
              known to be up. Setting this flag forces  dnsmasq  to  try  each
              query  with  each  server  strictly  in the order they appear in

              By default, when dnsmasq  has  more  than  one  upstream  server
              available, it will send queries to just one server. Setting this
              flag forces  dnsmasq  to  send  all  queries  to  all  available
              servers.  The  reply from the server which answers first will be
              returned to the original requestor.

              Reject (and log) addresses from upstream nameservers  which  are
              in  the private IP ranges. This blocks an attack where a browser
              behind a firewall  is  used  to  probe  machines  on  the  local

              Exempt from rebinding checks. This address range is
              returned by realtime black hole  servers,  so  blocking  it  may
              disable these services.

              Do  not detect and block dns-rebind on queries to these domains.
              The argument may be either a single domain, or multiple  domains
              surrounded  by  ’/’,  like  the  --server syntax, eg.  --rebind-

       -n, --no-poll
              Don’t poll /etc/resolv.conf for changes.

              Whenever /etc/resolv.conf is re-read, clear the DNS cache.  This
              is useful when new nameservers may have different data than that
              held in cache.

       -D, --domain-needed
              Tells dnsmasq to never forward queries for plain names,  without
              dots  or  domain  parts, to upstream nameservers. If the name is
              not known from /etc/hosts or DHCP then a "not found"  answer  is

       -S,                                                            --local,
              Specify  IP  address  of upstream servers directly. Setting this
              flag does not suppress reading of /etc/resolv.conf, use -R to do
              that.  If one or more optional domains are given, that server is
              used only for those domains and they are queried only using  the
              specified  server.  This is intended for private nameservers: if
              you have a nameserver on your network which deals with names  of
              the  form  at  then
              giving  the flag -S / will
              send  all  queries  for  internal  machines  to that nameserver,
              everything else will go to the servers in  /etc/resolv.conf.  An
              empty  domain  specification,  //  has  the  special  meaning of
              "unqualified names only" ie names without any dots  in  them.  A
              non-standard  port  may  be  specified as part of the IP address
              using a # character.  More than one -S  flag  is  allowed,  with
              repeated domain or ipaddr parts as required.

              More  specific  domains  take  precendence  over  less  specific
              domains,            so:             --server=/
              --server=/    will    send   queries   for
              * to, except *, which  will  go

              The   special  server  address  ’#’  means,  "use  the  standard
              servers",            so             --server=/
              --server=/ will send queries for * to
    , except  *  which  will  be  forwarded  as

              Also  permitted  is  a  -S  flag  which gives a domain but no IP
              address; this tells dnsmasq that a domain is local  and  it  may
              answer  queries from /etc/hosts or DHCP but should never forward
              queries on that domain to any  upstream  servers.   local  is  a
              synonym  for  server to make configuration files clearer in this

              The optional string after the @ character tells dnsmasq  how  to
              set  the  source of the queries to this nameserver. It should be
              an ip-address, which should  belong  to  the  machine  on  which
              dnsmasq is running otherwise this server line will be logged and
              then ignored, or an interface name.  If  an  interface  name  is
              given,  then  queries  to  the  server  will  be forced via that
              interface; if an ip-address is given then the source address  of
              the queries will be set to that address.  The query-port flag is
              ignored for any servers which have a  source  address  specified
              but  the  port  may  be specified directly as part of the source
              address. Forcing queries to an interface is not  implemented  on
              all platforms supported by dnsmasq.

       -A, --address=/<domain>/[domain/]<ipaddr>
              Specify  an  IP  address  to  return  for  any host in the given
              domains.  Queries in the domains are never forwarded and  always
              replied  to  with  the specified IP address which may be IPv4 or
              IPv6. To give both IPv4 and IPv6 addresses  for  a  domain,  use
              repeated  -A  flags.   Note  that  /etc/hosts  and  DHCP  leases
              override this for individual names. A common use of this  is  to
              redirect  the  entire  domain  to some friendly
              local web server to avoid banner ads. The  domain  specification
              works  in  the  same  was  as  for --server, with the additional
              facility that /#/ matches any domain. Thus  --address=/#/
              will  always  return  for  any  query not answered from
              /etc/hosts or DHCP and not sent to an upstream nameserver  by  a
              more specific --server directive.

       -m, --mx-host=<mx name>[[,<hostname>],<preference>]
              Return  an  MX  record  named  <mx  name>  pointing to the given
              hostname (if given), or the host specified  in  the  --mx-target
              switch  or,  if  that  switch  is  not  given, the host on which
              dnsmasq is running. The default is  useful  for  directing  mail
              from  systems on a LAN to a central server. The preference value
              is optional, and defaults to 1 if not given. More  than  one  MX
              record may be given for a host.

       -t, --mx-target=<hostname>
              Specify  the  default  target  for  the  MX  record  returned by
              dnsmasq. See --mx-host.  If --mx-target is given, but not  --mx-
              host,  then dnsmasq returns a MX record containing the MX target
              for MX queries on the hostname of the machine on  which  dnsmasq
              is running.

       -e, --selfmx
              Return  an  MX record pointing to itself for each local machine.
              Local machines are those in /etc/hosts or with DHCP leases.

       -L, --localmx
              Return an MX record pointing to the host given by mx-target  (or
              the machine on which dnsmasq is running) for each local machine.
              Local machines are those in /etc/hosts or with DHCP leases.

       -W,                                                              --srv-
              Return a SRV  DNS  record.  See  RFC2782  for  details.  If  not
              supplied,  the  domain  defaults to that given by --domain.  The
              default for the target domain is empty, and the default for port
              is  one  and  the  defaults for weight and priority are zero. Be
              careful if transposing data from  BIND  zone  files:  the  port,
              weight  and priority numbers are in a different order. More than
              one SRV record for a given service/domain is allowed,  all  that
              match are returned.

       -Y, --txt-record=<name>[[,<text>],<text>]
              Return  a  TXT  DNS  record. The value of TXT record is a set of
              strings, so  any number may be included, split by commas.

              Return a PTR DNS record.

              Return an NAPTR DNS record, as specified in RFC3403.

              Return a CNAME record which indicates  that  <cname>  is  really
              <target>.  There  are  significant limitations on the target; it
              must be a DNS name which is known to dnsmasq from /etc/hosts (or
              additional  hosts  files)  or  from DHCP. If the target does not
              satisfy this criteria, the whole cname  is  ignored.  The  cname
              must  be  unique,  but  it  is permissable to have more than one
              cname pointing to the same target.

              Return a DNS  record  associating  the  name  with  the  primary
              address  on the given interface. This flag specifies an A record
              for the given name in the same way as an /etc/hosts line, except
              that  the  address  is  not  constant,  but taken from the given
              interface. If the interface is  down,  not  configured  or  non-
              existent,  an  empty record is returned. The matching PTR record
              is also created, mapping the interface address to the name. More
              than  one  name  may  be associated with an interface address by
              repeating the flag; in that case the first instance is used  for
              the reverse address-to-name mapping.

       -c, --cache-size=<cachesize>
              Set  the  size  of  dnsmasq’s  cache.  The default is 150 names.
              Setting the cache size to zero disables caching.

       -N, --no-negcache
              Disable negative caching. Negative  caching  allows  dnsmasq  to
              remember  "no such domain" answers from upstream nameservers and
              answer identical queries without forwarding them again.

       -0, --dns-forward-max=<queries>
              Set the maximum number of concurrent DNS  queries.  The  default
              value  is  150,  which  should be fine for most setups. The only
              known situation where this needs to be increased is  when  using
              web-server  log file resolvers, which can generate large numbers
              of concurrent queries.

       -F,                                                             --dhcp-
       addr>,<end-addr>[,<netmask>[,<broadcast>]][,<lease time>]
              Enable the DHCP server. Addresses will be  given  out  from  the
              range  <start-addr>  to  <end-addr>  and from statically defined
              addresses given in dhcp-host  options.  If  the  lease  time  is
              given,  then  leases  will be given for that length of time. The
              lease time is in seconds, or minutes (eg 45m) or hours  (eg  1h)
              or "infinite". If not given, the default lease time is one hour.
              The minimum lease time  is  two  minutes.  This  option  may  be
              repeated,  with  different  addresses, to enable DHCP service to
              more than one network.  For  directly  connected  networks  (ie,
              networks  on which the machine running dnsmasq has an interface)
              the netmask is optional. It is, however, required  for  networks
              which  receive  DHCP  service  via  a relay agent. The broadcast
              address is always optional. It is always allowed  to  have  more
              than one dhcp-range in a single subnet.

              The  optional  set:<tag>  sets an alphanumeric label which marks
              this network so that dhcp options may be  specified  on  a  per-
              network  basis.   When  it is prefixed with ’tag:’ instead, then
              its meaning changes from setting a tag to matching it. Only  one
              tag  may  be set, but more than one tag may be matched.  The end
              address may be  replaced  by  the  keyword  static  which  tells
              dnsmasq  to  enable  DHCP  for the network specified, but not to
              dynamically allocate IP addresses: only hosts which have  static
              addresses  given  via  dhcp-host  or  from  /etc/ethers  will be
              served. The end address may be replaced by the keyword proxy  in
              which  case  dnsmasq  will  provide  proxy-DHCP on the specified
              subnet. (See pxe-prompt and pxe-service for details.)

              The interface:<interface name> section is not normally used. See
              the NOTES section for details of this.

       -G,                                                             --dhcp-
              Specify  per  host parameters for the DHCP server. This allows a
              machine  with  a  particular  hardware  address  to  be   always
              allocated  the  same  hostname,  IP  address  and  lease time. A
              hostname specified like this overrides any supplied by the  DHCP
              client  on  the  machine.  It  is  also  allowable  to ommit the
              hardware address and include the hostname, in which case the  IP
              address  and lease times will apply to any machine claiming that
              name.  For  example   --dhcp-host=00:20:e0:3b:13:af,wap,infinite
              tells   dnsmasq  to  give  the  machine  with  hardware  address
              00:20:e0:3b:13:af the name wap,  and  an  infinite  DHCP  lease.
              --dhcp-host=lap,  tells  dnsmasq to always allocate
              the machine lap the IP address

              Addresses allocated like this are not constrained to be  in  the
              range  given by the --dhcp-range option, but they must be in the
              same subnet as some valid dhcp-range.  For subnets  which  don’t
              need a pool of dynamically allocated addresses, use the "static"
              keyword in the dhcp-range declaration.

              It is allowed to use client  identifiers  rather  than  hardware
              addresses  to  identify  hosts  by  prefixing  with ’id:’. Thus:
              --dhcp-host=id:01:02:03:04,.....  refers to the host with client
              identifier 01:02:03:04. It is also allowed to specify the client
              ID as text, like this: --dhcp-host=id:clientidastext,.....

              The special option id:* means "ignore any client-id and use  MAC
              addresses only." This is useful when a client presents a client-
              id sometimes but not others.

              If a name appears in /etc/hosts, the associated address  can  be
              allocated  to  a  DHCP  lease,  but only if a --dhcp-host option
              specifying the name also exists. Only one hostname can be  given
              in a dhcp-host option, but aliases are possible by using CNAMEs.
              (See --cname ).

              The special keyword "ignore" tells dnsmasq to never offer a DHCP
              lease  to  a  machine.  The machine can be specified by hardware
              address,  client  ID   or   hostname,   for   instance   --dhcp-
              host=00:20:e0:3b:13:af,ignore  This  is  useful  when  there  is
              another DHCP server on the network which should be used by  some

              The  set:<tag>  contruct  sets  the  tag whenever this dhcp-host
              directive is in use. This can be used to selectively  send  DHCP
              options  just  for  this host. More than one tag can be set in a
              dhcp-host directive (but not in other places  where  "set:<tag>"
              is allowed). When a host matches any dhcp-host directive (or one
              implied by /etc/ethers) then the special  tag  "known"  is  set.
              This  allows  dnsmasq  to  be configured to ignore requests from
              unknown   machines   using   --dhcp-ignore=tag:!known   Ethernet
              addresses  (but  not client-ids) may have wildcard bytes, so for
              example --dhcp-host=00:20:e0:3b:13:*,ignore will  cause  dnsmasq
              to  ignore a range of hardware addresses. Note that the "*" will
              need to be escaped or quoted on a command line, but not  in  the
              configuration file.

              Hardware addresses normally match any network (ARP) type, but it
              is possible to restrict them to a single ARP type  by  preceding
              them   with   the   ARP-type   (in  HEX)  and  "-".  so  --dhcp-
              host=06-00:20:e0:3b:13:af, will only match  a  Token-Ring
              hardware  address,  since the ARP-address type for token ring is

              As a special case, it is  possible  to  include  more  than  one
              hardware             address.             eg:            --dhcp-
              host=11:22:33:44:55:66,12:34:56:78:90:12, This allows
              an IP address to be associated with multiple hardware addresses,
              and gives dnsmasq permission to abandon a DHCP lease to  one  of
              the hardware addresses when another one asks for a lease. Beware
              that this is a dangerous thing to do, it will only work reliably
              if  only one of the hardware addresses is active at any time and
              there is no  way  for  dnsmasq  to  enforce  this.  It  is,  for
              instance,  useful  to  allocate  a stable IP address to a laptop
              which has both wired and wireless interfaces.

              Read DHCP host information from the  specified  file.  The  file
              contains  information  about  one host per line. The format of a
              line is the same as text to the right of ’=’ in --dhcp-host. The
              advantage  of storing DHCP host information in this file is that
              it can be changed without re-starting dnsmasq: the file will  be
              re-read when dnsmasq receives SIGHUP.

              Read  DHCP  option  information  from  the  specified  file. The
              advantage of using this  option  is  the  same  as  for  --dhcp-
              hostsfile:  the  dhcp-optsfile  will  be  re-read  when  dnsmasq
              receives  SIGHUP.  Note  that  it  is  possible  to  encode  the
              information  in  a  --dhcp-boot  flag as DHCP options, using the
              options names bootfile-name, server-ip-address and  tftp-server.
              This allows these to be included in a dhcp-optsfile.

       -Z, --read-ethers
              Read  /etc/ethers  for  information  about  hosts  for  the DHCP
              server.  The  format  of  /etc/ethers  is  a  hardware  address,
              followed  by  either  a hostname or dotted-quad IP address. When
              read by dnsmasq these lines have  exactly  the  same  effect  as
              --dhcp-host options containing the same information. /etc/ethers
              is re-read when dnsmasq receives SIGHUP.

       -O,            --dhcp-option=[tag:<tag>,[tag:<tag>,]][encap:<opt>,][vi-
              Specify different or extra options to DHCP clients. By  default,
              dnsmasq sends some standard options to DHCP clients, the netmask
              and broadcast address are set to the same as  the  host  running
              dnsmasq,  and  the  DNS  server and default route are set to the
              address of the machine  running  dnsmasq.  If  the  domain  name
              option  has  been  set, that is sent.  This configuration allows
              these defaults to be overridden, or other options specified. The
              option,  to  be  sent  may  be  given  as a decimal number or as
              "option:<option-name>"  The  option  numbers  are  specified  in
              RFC2132  and  subsequent  RFCs. The set of option-names known by
              dnsmasq can be discovered by running "dnsmasq --help dhcp".  For
              example,  to  set  the  default  route option to, do
              --dhcp-option=3, or  --dhcp-option  =  option:router,
      and  to set the time-server address to,
              do --dhcp-option = 42, or --dhcp-option = option:ntp-
              server, The special address is taken to mean
              "the address of the machine running dnsmasq". Data types allowed
              are  comma separated dotted-quad IP addresses, a decimal number,
              colon-separated hex digits and a text string.  If  the  optional
              tags  are  given then this option is only sent when all the tags
              are matched.

              Special processing is done on a text argument for option 119, to
              conform  with  RFC  3397.  Text  or  dotted-quad IP addresses as
              arguments to option 120 are handled as per RFC 3361. Dotted-quad
              IP  addresses  which  are followed by a slash and then a netmask
              size are encoded as described in RFC 3442.

              Be careful: no checking is done that the correct  type  of  data
              for  the option number is sent, it is quite possible to persuade
              dnsmasq to generate illegal DHCP packets with injudicious use of
              this  flag.  When  the  value  is a decimal number, dnsmasq must
              determine how large the data item is. It does this by  examining
              the  option  number  and/or  the value, but can be overridden by
              appending a single letter flag as follows: b = one byte, s = two
              bytes,  i  = four bytes. This is mainly useful with encapsulated
              vendor class options (see below) where dnsmasq cannot  determine
              data  size  from  the  option number. Option data which consists
              solely of periods and digits will be interpreted by  dnsmasq  as
              an  IP  address, and inserted into an option as such. To force a
              literal string, use quotes. For instance when using option 66 to
              send  a  literal IP address as TFTP server name, it is necessary
              to do --dhcp-option=66,""

              Encapsulated Vendor-class options may also  be  specified  using
              --dhcp-option:           for           instance          --dhcp-
              option=vendor:PXEClient,1, sends the encapsulated  vendor
              class-specific option "mftp-address=" to any client whose
              vendor-class matches "PXEClient". The vendor-class  matching  is
              substring  based  (see  --dhcp-vendorclass  for  details).  If a
              vendor-class option (number 60) is sent by dnsmasq, then that is
              used  for  selecting  encapsulated  options in preference to any
              sent by the client. It  is  possible  to  omit  the  vendorclass
              completely;  --dhcp-option=vendor:,1,  in  which case the
              encapsulated option is always sent.

              Options may be encapsulated within other options:  for  instance
              --dhcp-option=encap:175,  190,  iscsi-client0  will  send option
              175, within which is the option 190.  If  multiple  options  are
              given  which  are  encapsulated with the same option number then
              they will be correctly combined into  one  encapsulated  option.
              encap:  and  vendor:  are  may not both be set in the same dhcp-

              The final variant on encapsulated options is "Vendor-Identifying
              Vendor  Options" as specified by RFC3925. These are denoted like
              this: --dhcp-option=vi-encap:2, 10, text The number in  the  vi-
              encap:  section  is  the IANA enterprise number used to identify
              this option.

              The address is not  treated  specially  in  encapsulated

              This  works in exactly the same way as --dhcp-option except that
              the option will always be sent, even if the client does not  ask
              for  it in the parameter request list. This is sometimes needed,
              for example when sending options to PXELinux.

              Disable re-use of the DHCP servername  and  filename  fields  as
              extra option space. If it can, dnsmasq moves the boot server and
              filename information (from dhcp-boot)  out  of  their  dedicated
              fields into DHCP options. This make extra space available in the
              DHCP packet for options but can, rarely, confuse old  or  broken
              clients.  This  flag forces "simple and safe" behaviour to avoid
              problems in such a case.

       -U, --dhcp-vendorclass=set:<tag>,<vendor-class>
              Map from a vendor-class string  to  a  tag.  Most  DHCP  clients
              provide  a  "vendor  class" which represents, in some sense, the
              type of host. This option maps vendor classes to tags,  so  that
              DHCP  options  may be selectively delivered to different classes
              of  hosts.  For  example  dhcp-vendorclass=set:printers,Hewlett-
              Packard  JetDirect  will  allow  options  to  be set only for HP
              printers like so:  --dhcp-option=tag:printers,3,  The
              vendor-class  string  is  substring  matched against the vendor-
              class supplied by the client, to allow fuzzy matching. The  set:
              prefix is optional but allowed for consistency.

       -j, --dhcp-userclass=set:<tag>,<user-class>
              Map  from a user-class string to a tag (with substring matching,
              like vendor classes). Most DHCP clients provide a  "user  class"
              which is configurable. This option maps user classes to tags, so
              that DHCP options may  be  selectively  delivered  to  different
              classes  of  hosts.  It is possible, for instance to use this to
              set a different printer server for hosts in the class "accounts"
              than for hosts in the class "engineering".

       -4, --dhcp-mac=set:<tag>,<MAC address>
              Map  from  a  MAC  address to a tag. The MAC address may include
              wildcards. For example  --dhcp-mac=set:3com,01:34:23:*:*:*  will
              set  the  tag  "3com" for any host whose MAC address matches the

       --dhcp-circuitid=set:<tag>,<circuit-id>,                        --dhcp-
              Map from RFC3046 relay agent options to tags. This data  may  be
              provided  by  DHCP  relay agents. The circuit-id or remote-id is
              normally given as colon-separated hex, but is also allowed to be
              a  simple  string.  If  an  exact  match is achieved between the
              circuit or agent ID and one provided by a relay agent,  the  tag
              is set.

              Map from RFC3993 subscriber-id relay agent options to tags.

       --dhcp-proxy[=<ip addr>]......
              A  normal  DHCP  relay agent is only used to forward the initial
              parts of a DHCP interaction to the DHCP server. Once a client is
              configured,  it  communicates  directly with the server. This is
              undesirable if the relay agent is addding extra  information  to
              the  DHCP packets, such as that used by dhcp-circuitid and dhcp-
              remoteid.  A full relay implementation  can  use  the  RFC  5107
              serverid-override  option  to  force  the DHCP server to use the
              relay as a full proxy, with all packets passing through it. This
              flag provides an alternative method of doing the same thing, for
              relays which don’t support RFC 5107. Given alone, it manipulates
              the  server-id  for all interactions via relays. If a list of IP
              addresses is  given,  only  interactions  via  relays  at  those
              addresses are affected.

       --dhcp-match=set:<tag>,<option     number>|option:<option     name>|vi-
              Without  a  value, set the tag if the client sends a DHCP option
              of the given number or name. When a value is given, set the  tag
              only  if the option is sent and matches the value. The value may
              be of the form "01:ff:*:02" in which case the value  must  match
              (apart  from  widcards)  but  the option sent may have unmatched
              data past the end of the value. The value may  also  be  of  the
              same  form  as  in  dhcp-option in which case the option sent is
              treated as an array, and one element must match, so


              will set the tag "efi-ia32" if the the number 6 appears  in  the
              list  of architectures sent by the client in option 93. (See RFC
              4578 for details.)  If the value is a string, substring matching
              is used.

              The   special  form  with  vi-encap:<enterpise  number>  matches
              against vendor-identifying  vendor  classes  for  the  specified
              enterprise.  Please  see RFC 3925 for more details of these rare
              and interesting beasts.

              Perform  boolean  operations  on  tags.  Any  tag  appearing  as
              set:<tag>  is  set if all the tags which appear as tag:<tag> are
              set, (or unset when tag:!<tag> is used) If no tag:<tag>  appears
              set:<tag>  tags are set unconditionally.  Any number of set: and
              tag: forms may appear, in any order.  Tag-if lines ares executed
              in  order,  so  if  the tag in tag:<tag> is a tag set by another
              tag-if, the line which sets the tag must precede the  one  which
              tests it.

       -J, --dhcp-ignore=tag:<tag>[,tag:<tag>]
              When  all  the  given tags appear in the tag set ignore the host
              and do not allocate it a DHCP lease.

              When all the given tags  appear  in  the  tag  set,  ignore  any
              hostname provided by the host. Note that, unlike dhcp-ignore, it
              is permissible to supply no  tags,  in  which  case  DHCP-client
              supplied  hostnames are always ignored, and DHCP hosts are added
              to the DNS using only dhcp-host configuration in dnsmasq and the
              contents of /etc/hosts and /etc/ethers.

              Generate  a  name  for  DHCP clients which do not otherwise have
              one, using the  MAC  address  expressed  in  hex,  seperated  by
              dashes.  Note that if a host provides a name, it will be used by
              preference to this, unless --dhcp-ignore-names is set.

              When all the given tags  appear  in  the  tag  set,  always  use
              broadcast  to communicate with the host when it is unconfigured.
              It is permissible to supply no  tags,  in  which  case  this  is
              unconditional.  Most  DHCP  clients which need broadcast replies
              set a flag in their requests so that this happens automatically,
              some old BOOTP clients do not.

       -M,           --dhcp-boot=[tag:<tag>,]<filename>,[<servername>[,<server
              Set BOOTP options to be returned by the DHCP server. Server name
              and address are optional: if not  provided,  the  name  is  left
              empty, and the address set to the address of the machine running
              dnsmasq. If dnsmasq is providing a TFTP service  (see  --enable-
              tftp ) then only the filename is required here to enable network
              booting.  If the optional tag(s) are given, they must match  for
              this configuration to be sent.

       text>[,<basename>|<bootservicetype>][,<server address>]
              Most uses of PXE boot-ROMS simply allow the PXE system to obtain
              an IP address and then download the file specified by  dhcp-boot
              and  execute  it.  However  the  PXE  system  is capable of more
              complex functions when supported by a suitable DHCP server.

              This specifies a boot option which may  appear  in  a  PXE  boot
              menu.  <CSA> is client system type, only services of the correct
              type will appear in a menu. The known  types  are  x86PC,  PC98,
              IA64_EFI,  Alpha,  Arc_x86, Intel_Lean_Client, IA32_EFI, BC_EFI,
              Xscale_EFI and X86-64_EFI; an integer  may  be  used  for  other
              types.  The parameter after the menu text may be a file name, in
              which case dnsmasq acts as a boot server  and  directs  the  PXE
              client  to  download  the  file  by  TFTP,  either from itself (
              enable-tftp must be set for this to work) or another TFTP server
              if  the final IP address is given.  Note that the "layer" suffix
              (normally ".0") is supplied by PXE, and should not be  added  to
              the  basename.  If  an  integer boot service type, rather than a
              basename is given,  then  the  PXE  client  will  search  for  a
              suitable  boot service for that type on the network. This search
              may be done by broadcast, or  direct  to  a  server  if  its  IP
              address  is  provided.   If  no boot service type or filename is
              provided (or a boot service type of 0  is  specified)  then  the
              menu  entry  will  abort  the  net  boot  procedure and continue
              booting from local media.

              Setting this provides a prompt to be displayed after  PXE  boot.
              If  the timeout is given then after the timeout has elapsed with
              no keyboard input, the  first  available  menu  option  will  be
              automatically  executed.  If  the timeout is zero then the first
              available menu item will be executed immediately. If  pxe-prompt
              is  ommitted  the  system  will wait for user input if there are
              multiple items in the menu, but boot  immediately  if  there  is
              only one. See pxe-service for details of menu items.

              Dnsmasq  supports  PXE  "proxy-DHCP",  in this case another DHCP
              server  on  the  network  is  responsible  for   allocating   IP
              addresses,  and dnsmasq simply provides the information given in
              pxe-prompt and pxe-service to allow  netbooting.  This  mode  is
              enabled using the proxy keyword in dhcp-range.

       -X, --dhcp-lease-max=<number>
              Limits  dnsmasq  to the specified maximum number of DHCP leases.
              The default is 1000. This limit is to prevent DoS  attacks  from
              hosts which create thousands of leases and use lots of memory in
              the dnsmasq process.

       -K, --dhcp-authoritative
              Should be set when dnsmasq is definitely the only DHCP server on
              a  network.  It changes the behaviour from strict RFC compliance
              so that DHCP requests on unknown leases from unknown  hosts  are
              not  ignored.  This  allows  new  hosts to get a lease without a
              tedious timeout under all circumstances. It also allows  dnsmasq
              to  rebuild  its  lease  database without each client needing to
              reacquire a lease, if the database is lost.

       --dhcp-alternate-port[=<server port>[,<client port>]]
              Change the ports used for DHCP from the default. If this  option
              is given alone, without arguments, it changes the ports used for
              DHCP from 67 and 68 to 1067 and 1068. If a  single  argument  is
              given,  that  port  number  is  used for the server and the port
              number plus one used for the client. Finally, two  port  numbers
              allows  arbitrary  specification of both server and client ports
              for DHCP.

       -3, --bootp-dynamic[=<network-id>[,<network-id>]]
              Enable dynamic allocation of IP addresses to BOOTP clients.  Use
              this  with  care, since each address allocated to a BOOTP client
              is leased forever, and therefore becomes permanently unavailable
              for  re-use  by other hosts. if this is given without tags, then
              it unconditionally enables dynamic allocation. With  tags,  only
              when the tags are all set. It may be repeated with different tag

       -5, --no-ping
              By default, the DHCP server  will  attempt  to  ensure  that  an
              address  in  not  in use before allocating it to a host. It does
              this by sending an ICMP echo request (aka "ping") to the address
              in  question.  If it gets a reply, then the address must already
              be in use, and another is tried. This flag disables this  check.
              Use with caution.

              Extra logging for DHCP: log all the options sent to DHCP clients
              and the tags used to determine them.

       -l, --dhcp-leasefile=<path>
              Use the specified file to store DHCP lease information.

       -6 --dhcp-script=<path>
              Whenever a new DHCP lease is created, or an old  one  destroyed,
              the  executable specified by this option is run.  <path> must be
              an absolute pathname, no PATH search occurs.  The  arguments  to
              the  process  are  "add", "old" or "del", the MAC address of the
              host, the IP address, and the hostname, if known. "add" means  a
              lease has been created, "del" means it has been destroyed, "old"
              is a notification of an existing lease when dnsmasq starts or  a
              change  to  MAC  address or hostname of an existing lease (also,
              lease length or expiry and client-id, if leasefile-ro  is  set).
              If  the  MAC address is from a network type other than ethernet,
              it    will    have    the    network    type    prepended,    eg
              "06-01:23:45:67:89:ab"  for  token  ring.  The process is run as
              root (assuming that dnsmasq was originally run as root) even  if
              dnsmasq is configured to change UID to an unprivileged user.

              The  environment  is inherited from the invoker of dnsmasq, with
              some or all of the following variables added.

              DNSMASQ_CLIENT_ID if the host provided a client-id.

              DNSMASQ_DOMAIN if the fully-qualified domain name of the host is
              known, this is set to the  domain part.

              If  the  client  provides  vendor-class, hostname or user-class,
              these      are      provided       in       DNSMASQ_VENDOR_CLASS
              DNSMASQ_SUPPLIED_HOSTNAME                                    and
              DNSMASQ_USER_CLASS0..DNSMASQ_USER_CLASSn variables, but only for
              "add"  actions  or "old" actions when a host resumes an existing
              lease,  since  these  data  are  not  held  in  dnsmasq’s  lease

              If dnsmasq was compiled with HAVE_BROKEN_RTC, then the length of
              the  lease  (in  seconds)  is  stored  in  DNSMASQ_LEASE_LENGTH,
              otherwise    the   time   of   lease   expiry   is   stored   in
              DNSMASQ_LEASE_EXPIRES. The number of seconds until lease  expiry
              is always stored in DNSMASQ_TIME_REMAINING.

              If  a  lease used to have a hostname, which is removed, an "old"
              event is generated with the new state of the lease, ie no  name,
              and  the  former  name  is  provided in the environment variable

              DNSMASQ_INTERFACE stores the name of the interface on which  the
              request  arrived; this is not set for "old" actions when dnsmasq

              DNSMASQ_RELAY_ADDRESS is set if the client used a DHCP relay  to
              contact dnsmasq and the IP address of the relay is known.

              DNSMASQ_TAGS   contains   all  the  tags  set  during  the  DHCP
              transaction, separated by spaces.

              All file descriptors are closed except stdin, stdout and  stderr
              which are open to /dev/null (except in debug mode).

              The  script is not invoked concurrently: at most one instance of
              the script is ever running (dnsmasq waits  for  an  instance  of
              script  to  exit  before running the next). Changes to the lease
              database are which require the script to be invoked  are  queued
              awaiting  exit  of  a running instance.  If this queueing allows
              multiple state changes occur to a single lease before the script
              can  be  run  then  earlier states are discarded and the current
              state of that lease is reflected when the script finally runs.

              At dnsmasq startup, the script will be invoked for all  existing
              leases as they are read from the lease file. Expired leases will
              be called  with  "del"  and  others  with  "old".  When  dnsmasq
              receives  a  HUP signal, the script will be invoked for existing
              leases with an "old " event.

              Specify the user as which to run the lease-change  script.  This
              defaults  to root, but can be changed to another user using this

       -9, --leasefile-ro
              Completely suppress use of the lease  database  file.  The  file
              will not be created, read, or written. Change the way the lease-
              change script (if one is provided) is called, so that the  lease
              database may be maintained in external storage by the script. In
              addition to the invocations  given in --dhcp-script  the  lease-
              change  script  is  called  once,  at  dnsmasq startup, with the
              single argument "init". When called like this the script  should
              write  the  saved  state  of  the  lease  database,  in  dnsmasq
              leasefile format, to  stdout  and  exit  with  zero  exit  code.
              Setting  this  option  also  forces the leasechange script to be
              called on changes to the client-id and lease length  and  expiry

              Treat  DHCP  request  packets  arriving  at  any  of the <alias>
              interfaces as if they had arrived at <interface>. This option is
              necessary  when  using  "old  style"  bridging on BSD platforms,
              since packets arrive at tap interfaces which don’t  have  an  IP

       -s, --domain=<domain>[,<address range>]
              Specifies  DNS  domains  for  the DHCP server. Domains may be be
              given unconditionally (without the IP range) or for  limited  IP
              ranges.  This has two effects; firstly it causes the DHCP server
              to return the domain to any hosts which request it, and secondly
              it  sets  the domain which it is legal for DHCP-configured hosts
              to claim. The intention is to constrain  hostnames  so  that  an
              untrusted  host on the LAN cannot advertise its name via dhcp as
              e.g. "" and capture traffic not meant for it. If no
              domain suffix is specified, then any DHCP hostname with a domain
              part (ie with a period) will be disallowed and logged. If suffix
              is  specified,  then  hostnames  with a domain part are allowed,
              provided the domain part matches the suffix. In addition, when a
              suffix  is  set  then  hostnames  without a domain part have the
              suffix added as an optional domain part. Eg on my network I  can
              set  and  have  a machine whose DHCP
              hostname is  "laptop".  The  IP  address  for  that  machine  is
              available     from     dnsmasq     both    as    "laptop"    and
              "". If the domain is given as  "#"  then
              the  domain  is  read  from  the  first  "search"  directive  in
              /etc/resolv.conf (or equivalent). The address range  can  be  of
              the  form <ip address>,<ip address> or <ip address>/<netmask> or
              just a single <ip address>. See --dhcp-fqdn which can change the
              behaviour of dnsmasq with domains.

              In  the  default  mode, dnsmasq inserts the unqualified names of
              DHCP clients into the DNS. For this reason, the  names  must  be
              unique,  even  if  two  clients  which have the same name are in
              different domains. If a second DHCP client appears which has the
              same  name  as an existing client, the name is transfered to the
              new client. If --dhcp-fqdn is set, this behaviour  changes:  the
              unqualified name is no longer put in the DNS, only the qualified
              name. Two DHCP clients with the same  name  may  both  keep  the
              name,  provided  that the domain part is different (ie the fully
              qualified names differ.) To ensure that all names have a  domain
              part,  there  must  be  at  least  --domain  without  an address
              specified when --dhcp-fqdn is set.

              Enable the TFTP server function. This is deliberately limited to
              that  needed  to net-boot a client. Only reading is allowed; the
              tsize and  blksize  extensions  are  supported  (tsize  is  only
              supported  in  octet  mode).  See  NOTES  section for use of the
              interface argument.

              Look for files to transfer using  TFTP  relative  to  the  given
              directory.  When  this is set, TFTP paths which include ".." are
              rejected, to stop clients getting outside  the  specified  root.
              Absolute  paths  (starting with /) are allowed, but they must be
              within the tftp-root. If  the  optional  interface  argument  is
              given,  the  directory  is  only used for TFTP requests via that

              Add the IP address of the TFTP client as a path component on the
              end  of  the  TFTP-root  (in  standard dotted-quad format). Only
              valid if a tftp-root  is  set  and  the  directory  exists.  For
              instance,  if  tftp-root  is "/tftp" and client requests
              file   "myfile"   then    the    effective    path    will    be
              "/tftp/"  if  /tftp/ exists or /tftp/myfile

              Enable TFTP  secure  mode:  without  this,  any  file  which  is
              readable by the dnsmasq process under normal unix access-control
              rules is available via TFTP.  When  the  --tftp-secure  flag  is
              given,  only files owned by the user running the dnsmasq process
              are accessible. If dnsmasq is being run as root, different rules
              apply:  --tftp-secure  has  no effect, but only files which have
              the world-readable bit set are accessible. It is not recommended
              to  run  dnsmasq  as  root  with TFTP enabled, and certainly not
              without specifying --tftp-root. Doing so can expose  any  world-
              readable file on the server to any host on the net.

              Set  the  maximum number of concurrent TFTP connections allowed.
              This defaults to  50.  When  serving  a  large  number  of  TFTP
              connections,   per-process   file   descriptor   limits  may  be
              encountered.  Dnsmasq  needs  one  file  descriptor   for   each
              concurrent  TFTP  connection  and one file descriptor per unique
              file  (plus  a  few  others).   So   serving   the   same   file
              simultaneously  to  n clients will use require about n + 10 file
              descriptors, serving different files simultaneously to n clients
              will  require about (2*n) + 10 descriptors. If --tftp-port-range
              is given, that can affect the number of concurrent  connections.

              Stop  the  TFTP  server  from negotiating the "blocksize" option
              with a client. Some buggy clients request this option  but  then
              behave badly when it is granted.

              A  TFTP  server listens on a well-known port (69) for connection
              initiation, but it also uses a  dynamically-allocated  port  for
              each  connection.  Normally  these  are allocated by the OS, but
              this  option  specifies  a  range  of  ports  for  use  by  TFTP
              transfers.  This  can  be  useful  when  TFTP  has to traverse a
              firewall. The start of the  range  cannot  be  lower  than  1025
              unless dnsmasq is running as root. The number of concurrent TFTP
              connections is limited by the size of the port range.

       -C, --conf-file=<file>
              Specify a different configuration file. The conf-file option  is
              also   allowed  in  configuration  files,  to  include  multiple
              configuration files.

       -7, --conf-dir=<directory>[,<file-extension>......]
              Read all the files  in  the  given  directory  as  configuration
              files.  If  extension(s) are given, any files which end in those
              extensions are skipped. Any files whose names end in ~ or  start
              with . or start and end with # are always skipped. This flag may
              be given on the command line or in a configuration file.


       At startup, dnsmasq reads /etc/dnsmasq.conf, if it exists. (On FreeBSD,
       the  file  is  /usr/local/etc/dnsmasq.conf  )  (but  see  the -C and -7
       options.) The format of this file consists  of  one  option  per  line,
       exactly as the long options detailed in the OPTIONS section but without
       the leading "--". Lines starting with # are comments and  ignored.  For
       options  which  may  only  be  specified  once,  the configuration file
       overrides the command line.  Quoting  is  allowed  in  a  config  file:
       between  " quotes the special meanings of ,:. and # are removed and the
       following escapes are allowed: \\ \" \t \e \b  \r  and  \n.  The  later
       corresponding to tab, escape, backspace, return and newline.


       When  it  receives a SIGHUP, dnsmasq clears its cache and then re-loads
       /etc/hosts and /etc/ethers and  any  file  given  by  --dhcp-hostsfile,
       --dhcp-optsfile  or  --addn-hosts.   The  dhcp  lease  change script is
       called for all existing DHCP leases. If --no-poll is  set  SIGHUP  also
       re-reads  /etc/resolv.conf.   SIGHUP does NOT re-read the configuration

       When it receives a SIGUSR1, dnsmasq writes  statistics  to  the  system
       log.  It  writes  the cache size, the number of names which have had to
       removed from the cache before they expired in order to  make  room  for
       new  names  and  the total number of names that have been inserted into
       the cache. For each upstream server it  gives  the  number  of  queries
       sent, and the number which resulted in an error. In --no-daemon mode or
       when full logging is enabled (-q), a complete dump of the  contents  of
       the cache is made.

       When it receives SIGUSR2 and it is logging direct to a file (see --log-
       facility ) dnsmasq will close and reopen the log file. Note that during
       this  operation,  dnsmasq  will  not  be running as root. When it first
       creates the logfile dnsmasq changes the ownership of the  file  to  the
       non-root  user it will run as. Logrotate should be configured to create
       a new log file with the ownership which matches the existing one before
       sending  SIGUSR2.   If TCP DNS queries are in progress, the old logfile
       will remain open in child processes which are handling TCP queries  and
       may  continue  to  be  written.  There is a limit of 150 seconds, after
       which all existing TCP processes will have expired: for this reason, it
       is  not  wise  to configure logfile compression for logfiles which have
       just been rotated. Using logrotate, the required options are create and

       Dnsmasq  is  a  DNS  query  forwarder: it it not capable of recursively
       answering arbitrary queries starting from the root servers but forwards
       such  queries  to  a  fully  recursive  upstream  DNS  server  which is
       typically   provided   by   an   ISP.   By   default,   dnsmasq   reads
       /etc/resolv.conf   to   discover  the  IP  addresses  of  the  upstream
       nameservers it should use, since the information  is  typically  stored
       there.  Unless  --no-poll is used, dnsmasq checks the modification time
       of /etc/resolv.conf (or equivalent if --resolv-file is  used)  and  re-
       reads  it  if  it  changes.  This  allows  the  DNS  servers  to be set
       dynamically  by  PPP  or  DHCP  since  both   protocols   provide   the
       information.   Absence of /etc/resolv.conf is not an error since it may
       not have been created before a PPP connection  exists.  Dnsmasq  simply
       keeps checking in case /etc/resolv.conf is created at any time. Dnsmasq
       can be told to parse more than one resolv.conf file. This is useful  on
       a  laptop,  where  both PPP and DHCP may be used: dnsmasq can be set to
       poll both /etc/ppp/resolv.conf and /etc/dhcpc/resolv.conf and will  use
       the  contents  of  whichever  changed  last, giving automatic switching
       between DNS servers.

       Upstream servers may also be specified on the command line  or  in  the
       configuration  file.  These  server  specifications  optionally  take a
       domain name which tells dnsmasq to use that server only to  find  names
       in that particular domain.

       In  order to configure dnsmasq to act as cache for the host on which it
       is running, put "nameserver"  in  /etc/resolv.conf  to  force
       local  processes  to  send  queries to dnsmasq. Then either specify the
       upstream servers directly to dnsmasq  using  --server  options  or  put
       their  addresses  real in another file, say /etc/resolv.dnsmasq and run
       dnsmasq with the -r /etc/resolv.dnsmasq option. This  second  technique
       allows for dynamic update of the server addresses by PPP or DHCP.

       Addresses  in /etc/hosts will "shadow" different addresses for the same
       names in the upstream DNS, so  ""  in  /etc/hosts
       will ensure that queries for "" always return even
       if queries in the upstream  DNS  would  otherwise  return  a  different
       address. There is one exception to this: if the upstream DNS contains a
       CNAME which points to a  shadowed  name,  then  looking  up  the  CNAME
       through  dnsmasq  will result in the unshadowed address associated with
       the target of the  CNAME.  To  work  around  this,  add  the  CNAME  to
       /etc/hosts so that the CNAME is shadowed too.

       The  tag  system  works  as  follows:  For  each  DHCP request, dnsmasq
       collects a set of valid tags  from  active  configuration  lines  which
       include  set:<tag>,  including one from the dhcp-range used to allocate
       the address, one from any matching dhcp-host (and "known"  if  a  dhcp-
       host  matches)  The  tag  "bootp"  is set for BOOTP requests, and a tag
       whose name is the name of the interface on which the request arrived is
       also set.

       Any  configuration lines which includes one or more tag:<tag> contructs
       will only be valid if all that tags are  matched  in  the  set  derived
       above.  Typically this is dhcp-option.  dhcp-option which has tags will
       be used in preference  to an untagged dhcp-option, provided that  _all_
       the  tags  match somewhere in the set collected as described above. The
       prefix ’!’ on a tag means ’not’ so  --dhcp=option=tag:!purple,3,
       sends  the  option when the tag purple is not in the set of valid tags.
       (If using this in a command line rather than a configuration  file,  be
       sure to escape !, which is a shell metacharacter)

       Note  that  for dhcp-range both tag:<tag> and set:<tag> are allowed, to
       both select the range in use based on (eg) dhcp-host, and to affect the
       options sent, based on the range selected.

       This  system evolved from an earlier, more limited one and for backward
       compatibility "net:" may be used instead of "tag:" and  "set:"  may  be
       omitted.  (Except  in  dhcp-host,  where  "net:" may be used instead of
       "set:".) For the same reason,  ’#’  may  be  used  instead  of  ’!’  to
       indicate NOT.

       The  DHCP  server  in  dnsmasq  will  function  as a BOOTP server also,
       provided that the MAC address and IP address  for  clients  are  given,
       either  using  dhcp-host configurations or in /etc/ethers , and a dhcp-
       range configuration option is present to activate the DHCP server on  a
       particular  network.  (Setting  --bootp-dynamic  removes  the  need for
       static address mappings.) The filename parameter in a BOOTP request  is
       used  as  a  tag, as is the tag "bootp", allowing some control over the
       options returned to different classes of hosts.

       dhcp-range    may    have    an    interface    name    supplied     as
       "interface:<interface-name>". The semantics if this are as follows: For
       DHCP, if any other dhcp-range exists _without_ an interface name,  then
       the  interface  name  is  ignored  and  and  dnsmasq  behaves as if the
       interface parts did not exist,  otherwise  DHCP  is  only  provided  to
       interfaces  mentioned in dhcp-range declarations. For DNS, if there are
       no --interface or --listen-address flags, behaviour is unchanged by the
       interface  part.  If  either of these flags are present, the interfaces
       mentioned in dhcp-ranges are added to the set which get DNS service.

       Similarly, enable-tftp may take an interface name, which  enables  TFTP
       only  for  a  particular  interface,  ignoring --interface or --listen-
       address flags. In addition  --tftp-secure  and  --tftp-unique-root  and
       --tftp-no-blocksize  are  ignored for requests from such interfaces. (A
       --tftp-root directive giving a root path and  an  interface  should  be
       provided too.)

       These  rules may seem odd at first sight, but  they allow a single line
       of the form  "dhcp-range=interface:virt0,,"  to
       be  added  to  dnsmasq  configuration  which then supplies DHCP and DNS
       services  to  that  interface,  without  affecting  what  services  are
       supplied  to other interfaces and irrespective of the existance or lack
       of   "interface=<interface>"   lines   elsewhere   in    the    dnsmasq
       configuration.  "enable-tftp=virt0" and "tftp-root=<root>,virt0" do the
       same job for TFTP.
        The idea is that such a line can be added automatically by libvirt  or
       equivalent systems, without disturbing any manual configuration.


       0  -  Dnsmasq  successfully  forked  into the background, or terminated
       normally if backgrounding is not enabled.

       1 - A problem with configuration was detected.

       2 - A problem with network access occurred (address in use, attempt  to
       use privileged ports without permission).

       3   -   A   problem  occurred  with  a  filesystem  operation  (missing
       file/directory, permissions).

       4 - Memory allocation failure.

       5 - Other miscellaneous problem.

       11 or greater - a non zero return code was  received  from  the  lease-
       script  process "init" call. The exit code from dnsmasq is the script’s
       exit code with 10 added.


       The default  values  for  resource  limits  in  dnsmasq  are  generally
       conservative,  and  appropriate  for  embedded router type devices with
       slow processors and limited memory. On more  capable  hardware,  it  is
       possible  to  increase  the  limits,  and handle many more clients. The
       following applies to dnsmasq-2.37: earlier versions did  not  scale  as

       Dnsmasq  is  capable  of  handling DNS and DHCP for at least a thousand
       clients. The DHCP lease times should not be very short (less  than  one
       hour).  The  value of --dns-forward-max can be increased: start with it
       equal to the number of clients and increase if  DNS  seems  slow.  Note
       that  DNS  performance  depends  too on the performance of the upstream
       nameservers. The size of the DNS cache may be increased: the hard limit
       is  10000  names  and the default (150) is very low. Sending SIGUSR1 to
       dnsmasq makes it log information which is useful for tuning  the  cache
       size. See the NOTES section for details.

       The   built-in  TFTP  server  is  capable  of  many  simultaneous  file
       transfers: the absolute limit is related to the number of  file-handles
       allowed  to  a  process  and the ability of the select() system call to
       cope with large numbers of file handles. If the limit is set  too  high
       using  --tftp-max it will be scaled down and the actual limit logged at
       start-up. Note that more transfers are possible when the same  file  is
       being sent than when each transfer sends a different file.

       It  is possible to use dnsmasq to block Web advertising by using a list
       of known banner-ad servers, all resolving to or,  in
       /etc/hosts  or  an  additional  hosts  file. The list can be very long,
       dnsmasq has been tested successfully with one million names. That  size
       file needs a 1GHz processor and about 60Mb of RAM.


       Dnsmasq  can  be  compiled to support internationalisation. To do this,
       the make targets "all-i18n" and "install-i18n" should be  used  instead
       of  the standard targets "all" and "install". When internationalisation
       is compiled in, dnsmasq will produce log messages in the local language
       and  support  internationalised  domain  names  (IDN).  Domain names in
       /etc/hosts, /etc/ethers and /etc/dnsmasq.conf which  contain  non-ASCII
       characters   will   be   translated   to   the   DNS-internal  punycode
       representation. Note that dnsmasq  determines  both  the  language  for
       messages  and the assumed charset for configuration files from the LANG
       environment variable. This should be set to the system default value by
       the  script which is responsible for starting dnsmasq. When editing the
       configuration files, be careful to do so using only the  system-default
       locale  and  not  user-specific one, since dnsmasq has no direct way of
       determining the charset in use, and must assume that it is  the  system











       hosts(5), resolver(5)


       This manual page was written by Simon Kelley <>.