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RESOLVCONF(8) System Manager's Manual RESOLVCONF(8) NAME resolvconf -- a framework for managing multiple DNS configurations SYNOPSIS resolvconf -I resolvconf [-m metric] [-p] [-x] -a key <file resolvconf -C pattern resolvconf -c pattern resolvconf [-f] -d key resolvconf [-x] -iLlp pattern resolvconf -u resolvconf --version DESCRIPTION resolvconf manages resolv.conf(5) files from multiple sources, such as DHCP and VPN clients. Traditionally, the host runs just one client and that updates /etc/resolv.conf. More modern systems frequently have wired and wireless interfaces and there is no guarantee both are on the same network. With the advent of VPN and other types of networking daemons, many things now contend for the contents of /etc/resolv.conf. resolvconf solves this by letting the daemon send their resolv.conf(5) file to resolvconf via stdin(4) with the argument -a key instead of the filesystem. resolvconf then updates /etc/resolv.conf as it thinks best. If /etc/resolv.conf already exists and the top line does not match the expected signature, then resolvconf will refuse to update it unless the -u update command is given. When a local resolver other than libc is installed, such as dnsmasq(8) or named(8), then resolvconf will supply files that the resolver should be configured to include. At it's heart, resolvconf is a key/value store for resolv.conf files. Each entry must have a unique key and should be expressed as interface.protocol so that it's easy to tell from where the resolv.conf file came from. This also allows using pattern matching such as interface.* to match all protocols running on the interface. For exam- ple, a modern system will likely run DHCP, RA and DHCPv6 which could be from separate programs or one program running many protocols. However, this is not a fixed requirement, resolvconf will work with any key name and it should be treated as an opaque value outside of resolvconf. resolvconf can mark a resolv.conf as private and optionally non-search- able. This means that the name servers listed in that resolv.conf are only used for queries against the domain/search listed in the same file and if non-searchable then the domain/search listed are excluded from the global search list defined in /etc/resolv.conf. This only works when a local resolver other than libc is installed. See resolvconf.conf(5) for how to configure resolvconf to use a local name server and how to remove the private marking. resolvconf can mark a resolv.conf as exclusive. Only the latest exclu- sive key is used for processing, otherwise all are. When a configuration source goes away, such as an interface going down or a VPN stopping, it should then call resolvconf with -d key arguments to clean up the resolv.conf it added previously. For systems that sup- port the concept of persisting configuration when the source is sus- pended, such as the carrier going down, then it should instead call resolvconf with -C key arguments to deprecate the entry -c key to acti- vate the entry when it comes back again. This only affects the order in which the resolv.conf entries are processed. Here are some options for the above commands: -f Ignore non existent resolv.conf entries. Only really use- ful for deleting. -m metric Set the metric of the resolv.conf entry when adding it, default of 0. Lower metrics take precedence. This af- fects the default order of entires when listed. -p [pattern] Marks the resolv.conf as private if the -a command is given, otherwise resolv.conf entries having their key matching pattern are listed. If an extra -p is given then the resolv.conf is marked as non-searchable as well. -x Mark the resolv.conf as exclusive when adding, otherwise only use the latest exclusive key. resolvconf has some more commands for general usage: -i [pattern] List the keys stored, optionally matching pattern, we have resolv.conf files for. If the -L option is given first, then the keys will be list post-processed. -L [pattern] List the resolv.conf files we have, post-processed by the resolvconf.conf(5) configuration. If pattern is specified then we list the files for the keys which match it. -l [pattern] List the resolv.conf files we have. If pattern is speci- fied then we list the files for the keys which match it. that match it. -u Force resolvconf to update all its subscribers. resolvconf does not update the subscribers when adding a resolv.conf that matches what it already has for that key. --version Echo the resolvconf version to stdout. resolvconf also has some commands designed to be used by its sub- scribers and system startup: -I Initialise the state directory /var/run/resolvconf. This should be called after the base state directory has either been cleaned out or mounted as a memory backed filesystem during the initial boot sequence before any daemon has the chance to call resolvconf. -R Echo the command used to restart a service. -r service If the service is running then restart it. If the service does not exist or is not running then zero is returned, otherwise the result of restarting the service. -v Echo variables DOMAINS, SEARCH and NAMESERVERS so that the subscriber can configure the resolver easily. -V Same as -v except that only the information configured in resolvconf.conf(5) is set. RESOLV.CONF ORDERING For resolvconf to work effectively, it has to process the resolv.conf entries in the correct order. resolvconf first processes keys from the key_order list, then entries without a metric and that match the dynamic_order list, then entries with a metric in order and finally the rest in the operating systems lexical order. See resolvconf.conf(5) for details on these lists. PROTOCOLS Here are some suggested protocol tags to use for each resolv.conf dhcp Dynamic Host Configuration Protocol. ppp Point-to-Point Protocol. ra IPv6 Router Advertisement. dhcp6 Dynamic Host Configuration Protocol, version 6. IMPLEMENTATION NOTES If a subscriber has the executable bit then it is executed otherwise it is assumed to be a shell script and sourced into the current environ- ment in a subshell. This is done so that subscribers can remain fast, but are also not limited to the shell language. Portable subscribers should not use anything outside of /bin and /sbin because /usr and others may not be available when booting. Also, it would be unwise to assume any shell specific features. ENVIRONMENT IF_METRIC If the -m option is not present then we use IF_METRIC for the metric. IF_PRIVATE Marks the resolv.conf as private. IF_NOSEARCH Marks the resolv.conf as non-searchable. IF_EXCLUSIVE Marks the resolv.conf as exclusive. FILES /etc/resolv.conf.bak Backup file of the original resolv.conf. /usr/local/etc/resolvconf.conf Configuration file for resolvconf. /usr/local/libexec/resolvconf Directory of subscribers which are run every time resolvconf adds, deletes or updates. /usr/local/libexec/resolvconf/libc.d Directory of subscribers which are run after the libc subscriber is run. /var/run/resolvconf State directory for resolvconf. NOTES Domain labels are assumed to be in ASCII and are converted to lower case to avoid duplicate zones when given differing case from different sources. When running a local resolver other than libc, you will need to config- ure it to include files that resolvconf will generate. You should con- sult resolvconf.conf(5) for instructions on how to configure your re- solver. SEE ALSO resolver(3), stdin(4), resolv.conf(5), resolvconf.conf(5) HISTORY This implementation of resolvconf is called openresolv and is fully command line compatible with Debian's resolvconf, as written by Thomas Hood. AUTHORS Roy Marples <roy@marples.name> BUGS Please report them to http://roy.marples.name/projects/openresolv FreeBSD ports 15.quarterly June 26, 2025 RESOLVCONF(8)
NAME | SYNOPSIS | DESCRIPTION | RESOLV.CONF ORDERING | PROTOCOLS | IMPLEMENTATION NOTES | ENVIRONMENT | FILES | NOTES | SEE ALSO | HISTORY | AUTHORS | BUGS
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