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Manual Reference Pages  -  DNRD (8)


dnrd - proxy name server



dnrd [-a localaddress | --address=localaddress] [-b | --load-balance] [-B BLACKLIST | --blacklist=BLACKLIST] [-c (off|[low:]high) | --cache=(off|[low:]high)] [-d LEVEL | --debug=LEVEL] [-h | --help] [-i | --ignore] [-k | --kill] [-l | --log] [-m (off|FILE) | --master=(off|FILE)] [-M N | --max-sock=N] [-r N | --retry=N] [-R DIR | --dnrd-root=DIR] [-s ipaddr(:domain) | --server=ipaddr(:domain)] [-S N[+] | --stats=N[+]] [-t N | --timeout=N] [-u userid | --uid=userid] [-v | --version]


dnrd is a proxying nameserver. It forwards DNS queries to the appropriate nameserver, but can also act as the primary nameserver for a subnet behind a firewall. Proxying is configured on the command line using the -s option. By default, dnrd will act as the primary nameserver for hosts found in /usr/local/etc/dnrd/master and queries to hostnames listed in /usr/local/etc/dnrd/blacklist will be answered with a "host not found".


Bind only to the interface with the specified address. By default dnrd binds to everything.

Turn on load balancing. All forward servers (specified with -s) after this option will load balance in a round robin scheme. By default, dnrd will use the next server in the list if the first times out. As soon as the first is reactivated, it will be used again. With -b option, dnrd will use next active server as soon a request is served. If a server times out it will be deactivated and will not be used until it comes back. As soon it is reactivated it will join the list.

Note that if there are no servers specified with -s after the -b, this will do nothing at all.

  Blacklist all hostnames listed in the file BLACKLIST. Queries to hosts listed in this file will be answered with "host not found". The file BLACKLIST is specified relative to the DNRD chroot directory (defaults to /usr/local/etc/dnrd). By default dnrd will look for a file named "blacklist".

-c (off|[low:]high)
  This option can be used to either turn off caching of DNS responses, or to change the high and low watermarks. With the high/low water mark option, cached entries are purged when the number of responses reaches the high-water mark, and they will be purged until the number of cached responses reaches the low-water mark, purging the oldest first. By default, caching is on, with low and high water-marks of 800 and 1000 respectively.

This turns on debugging level LEVEL. The dnrd process will not fork into the background and print out debugging information in the current console. Supported debug levels are 1-4 The higher level, the more debug info is printed.

The -l option can be used to force dnrd to run in the background and log debug info to syslog.

Sending signal SIGUSR1 will toggle the debug level between level 0 (no debugging) and level 3.

Prints usage information

Ignore cache for deactivated servers. If a forward DNS server times out and gets deactivated, all cache entries for this server are ignored. This helps avoid network timeout delays when dnrd serves a offline/dialup network.

Kills the currently running dnrd process.

Send all messages to syslog. dnrd uses the deamon facility. If used with the -d flag, this option will cause dnrd to fork and run in the background, logging all debugging messages to syslog.

-m (off|FILE)
  dnrd can act as the primary name server for a number of hosts. By default, it will read in /usr/local/etc/dnrd/master to determine how this is done. This option specifies another file than /usr/local/etc/dnrd/master or turns off all primary server functionality. Sending dnrd signal -HUP will make dnrd try to re-read the master file unless this is option is set to "off". Therefore, the master file have to be within the dnrd-root. the file is specified relative to dnrd-root.

-M N
Set the maximum allowed open sockets. Default is 200.

-r N
Set the retry interval time. When a forward DNS server times out it is deactivated. (use the -t option to set the timeout value) dnrd will try to send a request for localhost every N seconds. As soon there are a respose from a deactivated server, it is reactivated. The default value is 10 seconds. Setting this to zero will make dnrd to never deactivate a server.

Set the dnrd-root to DIR. dnrd will chroot to this directory at startup so all files, masterfile and blacklist, must be here. This option overrides the environment variable DNRD_ROOT. Default dnrd-root is /usr/local/etc/dnrd.

-s ipaddr(:domain)
  Add a forward DNS server. If -s is used multiple times, the first is the primary DNS server and the rest are backup servers. If the primary DNS server times out, it is deactivated and the next specified server (that is active) is used until the previous gets reactivated.

The domain option allows dnrd to determine which DNS server should get the query based on the domain name in the query. This is useful when you have an internet connection and a vpn connection to work, for instance. Several servers with the same domain might be specified and then will they work as backup servers.

If the -b option is specified, then all servers specified after the -b option are load balanced per domain.

-S N[+]
Print statistics about cache hits, cache misses and timeouts to syslog every N seconds. If + is specified, the counters will not be reset after the print.

-t N
Set the timeout value for forward DNS servers. If a server don’t respond to a query within N seconds it is deactivated. The default value is 12

Setting this to zero will make dnrd to never deactivate a server because of timeouts. However, a server might be deactivated if sendto fails.

-u userid
Set the UID that dnrd will run as. By default, dnrd tries to switches to uid dnrd after starting up.

Prints out the version number.


The TTL’s are not respected for the cache.



This file is used to configure dnrd as a primary nameserver.


Hosts listed in this file are blacklisted.


The currently-running dnrd process’ pid is placed into this file. It is needed to allow new dnrd processes to find and kill the currently running process.


The original version of dnrd was written by Brad Garcia Other contributors are listed in the HISTORY file included with the source code.

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DNRD v2.20 DNRD (8) Domain Name Relay Daemon

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