Fix DNS resolving on Debian

[conradgg]

Fix DNS resolving on Debian after installed resolvconf #479

[lnedry]

In Debian 12 resolvconf does not have a -u option and will fail if used.

[sskras]

@lnedry, are you use? On my box I run Proxmox which is based on Debian 12.10:

$ cat /etc/debian_version
12.10

Here -u is present:

$ sudo resolvconf
resolvconf: Error: Command not recognized
Usage: resolvconf COMMAND

Manage nameserver information.

Commands:
  -a IFACE               Add DNS configuration for IFACE from stdin.
  -d IFACE               Delete DNS configuration for IFACE.
  -u                     Run update actions (e.g. regenerate resolv.conf).
  -i                     List interfaces providing DNS configuration.
  --list, -l             Show DNS configuration for each interface.
  --enable-updates       Enable updates; run update actions if any are pending.
  --disable-updates      Disable updates until re-enabled.
  --updates-are-enabled  Return 0 if updates are enabled, 1 otherwise.
  --version              Print the resolvconf version.
  --help, -h             Print this help text.

The IFACE argument may not contain spaces, slashes, an initial dot, an initial
hyphen or an initial tilde. IFACE is conventionally formed from the interface
name, a dot, and the name of the interface configuration program (e.g. dhclient)
or the address family name (e.g. inet or inet6): eth0.dhclient, wlan0.inet6 etc.

... and it works just fine:

$ ping www.vu.lt
ping: www.vu.lt: Temporary failure in name resolution
$ sudo resolvconf -l
# resolv.conf from original.resolvconf
search self
nameserver 8.8.8.8

$ sudo resolvconf -u

$ ping www.vu.lt

PING web9waf.vu.lt (158.129.163.49) 56(84) bytes of data.
64 bytes from 158.129.163.49 (158.129.163.49): icmp_seq=1 ttl=247 time=2.22 ms
64 bytes from 158.129.163.49 (158.129.163.49): icmp_seq=2 ttl=247 time=2.56 ms
64 bytes from 158.129.163.49 (158.129.163.49): icmp_seq=3 ttl=247 time=2.19 ms
^C
--- web9waf.vu.lt ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 2.188/2.321/2.560/0.168 ms

Version of resolvconf I am currently running seems to be 1.91+nmu1:

$ /sbin/resolvconf --version
Debian resolvconf 1.91+nmu1
Copyright:
  2003-2017 Thomas Hood <jdthood@gmail.com>
License: GPL-2+