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Paul Wellner Bou avatar Ubuntu

Where is the resolvconf database, and how to reset it?

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Paul Wellner Bou

I am running Ubuntu 21.10 Desktop. For my work, I have to jump between different VPNs, and in the past I had to adjust DNS nameservers for some of them, too. I did this just with editing my /etc/resolv.conf file.

I do not need this anymore, but somehow this nameserver IP is still stored somewhere in resolvconf's configuration. And I was not able to find out where resolvconf is storing these IPs.

For example, my current /etc/resolv.conf:

nameserver 1.1.1.1
nameserver 8.8.4.4
nameserver 1.0.0.1

If I run resolvconf -u this changes the file to:

nameserver 10.12.1.1
nameserver 1.1.1.1
nameserver 1.0.0.1

Where the first is the IP I would like to get rid of completely.

While resolvonf -l is listing:

resolvconf -l
# resolv.conf from <my current connected VPN>
nameserver 1.1.1.1
nameserver 1.0.0.1

I don't have any more custom configuration in /etc/network/interfaces:

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

resolvectl status only contains two items with DNS servers:

Global
         Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
  resolv.conf mode: foreign
Current DNS Server: 1.1.1.1
       DNS Servers: 1.1.1.1 8.8.4.4 1.0.0.1

Link 2 (wlp59s0)
    Current Scopes: DNS
         Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 8.8.8.8
       DNS Servers: 8.8.8.8
        DNS Domain: --

My resolvectl version:

$ resolvectl --version
systemd 248 (248.3-1ubuntu8.2)
+PAM +AUDIT +SELINUX +APPARMOR +IMA +SMACK +SECCOMP +GCRYPT +GNUTLS -OPENSSL +ACL +BLKID +CURL +ELFUTILS -FIDO2 +IDN2 -IDN +IPTC +KMOD +LIBCRYPTSETUP -LIBFDISK +PCRE2 -PWQUALITY -P11KIT -QRENCODE +BZIP2 +LZ4 +XZ +ZLIB +ZSTD -XKBCOMMON +UTMP +SYSVINIT default-hierarchy=unified

resolconf version:

$ resolvconf --version
openresolv 3.12.0

Where is the "resolvconf database" or cache, where is resolvconf -u getting this IP from? How do I reset it to "factory settings"?

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dns
in flag
matigo
Does `resolvectl flush-caches` do anything? If not, what is the Terminal output of `resolvectl status`?
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Paul Wellner Bou avatar
in flag
Paul Wellner Bou
I added the output of `resolvectl status`. Flushing caches does not change anything.
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David avatar
cn flag
David
Latest version is not a version number. There are several that could be called latest and is it desktop or server?
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Paul Wellner Bou avatar
in flag
Paul Wellner Bou
True, sorry. Added the missing information.
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muru avatar
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muru
I don't think recent versions of Ubuntu even use `resolvconf` the program. It's `systemd-resolved` that's usually used by default. If you're using `resolvconf`, then you must be manually configuring it using the files in `/etc/resolvconf/`.
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Paul Wellner Bou avatar
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Paul Wellner Bou
How can I check this? I don't have anything configured in `/etc/resolconf/*`. But anyway... somewhere there is a place where the `10.*` IP is still saved, and where `resolvconf -u` is reading it from. And I really would like to know where.
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Paul Wellner Bou avatar Ubuntu
in flag
Paul Wellner Bou

I think I found it. Beside resolv.conf there is another file in /etc/: resolvconf.conf, and in this file I had the nameserver IP.

resolv_conf=/etc/resolv.conf
# If you run a local name server, you should uncomment the below line and
# configure your subscribers configuration files below.
name_servers=10.12.1.1
#name_servers=127.0.0.1

I don't know how it ended up here, but removing it there fixes my problem.

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