Jayctheriot: Created page with "Copy/pasted from https://unix.stackexchange.com/questions/694764/how-to-configure-resolv-conf `resolvconf` was/is a tool designed to allow updates to `/etc/resolv.conf` file from multiple sources (e.g. DHCP, static configuration by sysadmin, VPN clients, installation of a local DNS server...) in a way that allows the settings from each source to be reverted without interference to the other sources. It also allows setting priorities for each DNS co..."

2025-05-08T10:33:39Z

Created page with "Copy/pasted from https://unix.stackexchange.com/questions/694764/how-to-configure-resolv-conf <code>resolvconf</code> was/is a tool designed to allow updates to <code>/etc/resolv.conf</code> file from multiple sources (e.g. DHCP, static configuration by sysadmin, VPN clients, installation of a local DNS server...) in a way that allows the settings from each source to be reverted without interference to the other sources. It also allows setting priorities for each DNS co..."

New page

Copy/pasted from https://unix.stackexchange.com/questions/694764/how-to-configure-resolv-conf

<code>resolvconf</code> was/is a tool designed to allow updates to <code>/etc/resolv.conf</code> file from multiple sources (e.g. DHCP, static configuration by sysadmin, VPN clients, installation of a local DNS server...) in a way that allows the settings from each source to be reverted without interference to the other sources. It also allows setting priorities for each DNS configuration source, so that whenever there are more than three DNS server candidates, only the top three candidates will get chosen.

(Unless DNS timeouts are adjusted from defaults, only three query attempts can be made before the query times out, so configuring more than three DNS servers in <code>/etc/resolv.conf</code> is not typically useful.)

However, I think Ubuntu & Mint have migrated to using <code>systemd-resolved</code> instead of the classic <code>glibc</code> DNS resolver. This is true if the <code>hosts:</code> line in <code>/etc/nsswitch.conf</code> has <code>resolve</code> instead of or before <code>dns</code>. This configuration will route any DNS queries performed using glibc's hostname resolution API directly to <code>systemd-resolved</code> without checking <code>/etc/resolv.conf</code> at all. (Technically, <code>libnss_resolve.so</code> is used instead of <code>libnss_dns.so</code>.)

But your system may have some legacy applications that won't use <code>glibc</code>, or DNS diagnostic programs (<code>nslookup</code>, <code>dig</code> etc.) which will implement their own DNS queries, but will read <code>/etc/resolv.conf</code> to find out the default DNS server(s) to use. Because of this, <code>systemd-resolved</code> will by default offer a DNS-server-like interface at <code>127.0.0.53:53</code> and (unless this compatibility interface is disabled) will configure <code>/etc/resolv.conf</code> with a <code>nameserver 127.0.0.53</code> line, so that even the special cases will end up using <code>systemd-resolved</code>.

<code>resolvectl</code> is primarily a tool for managing <code>systemd-resolved</code>, whose functionality is a superset of (the classic <code>libnss_dns.so</code> resolver library + <code>resolvconf</code>). The <code>resolvectl</code> command has some compatibility with <code>resolvconf</code>, however the compatibility is not perfect: instead of modifying existing files in <code>/etc/resolvconf/resolv.conf.d/</code> or adding a new file to <code>[/var]/run/resolvconf/interface/</code> and then running <code>resolvconf -u</code>, you can supply per-interface DNS server configuration by <code>resolvectl dns <interface name> 1.1.1.1 8.8.8.8</code>, <code>resolvectl domain <interface name> domain.name.example</code> etc.

Since you seem to have both <code>resolvconf</code> and <code>systemd-resolved</code> installed, you may have the same situation as in Debian 11: <code>man resolvconf</code> will actually display the man page of <code>resolvectl</code>, including its compatibility notes. To view the man page of actual <code>resolvconf</code>, you'll need to type <code>man 8 resolvconf</code>.

The "unstable" in the output of <code>sudo apt changelog resolvconf</code> doesn't mean that version is unstable ''now'': it means ''at the time that change was made'' that version was in Debian <code>unstable</code>. For security bugfixes, you would see <code><releasename>-security</code> in place of <code>unstable</code>. The changelogs are part of the history of the individual package: they won't be rewritten as the package moves from Debian unstable to testing and onward to stable, or from unstable/testing to Ubuntu, Mint or other distributions which draw from Debian.

Resolv.conf - Revision history