DNS & dependencies removed from Webmin via a package uninstall. ERR "Temporary failure name resolution"

[nivllc]

SYSTEM INFORMATION
OS type and version	Ubuntu 22 LTS
Webmin version	Webmin 2.103
Virtualmin version	Virtualmin 7.7
Related packages	Bind DNS Server && Dependencies

Hello Virtualmin team,

After hours of troubleshooting and countless attempts in various methods, provided by: forums, support, docs, internet, etc. I have yet to resolve my issue in regards to: “Temporary failure in name resolution”.

10/30:

I removed, via the Webmin module, a Software Package: Cyrus and dependencies; upon doing so, the server froze and did not complete/execute thoroughly. Upon restart, I seem to have lost ‘connection’ to the DNS server (not installed or so it says). The server can not resolve nameservers, and as usual, Ubuntu Sever (on text gui) can not connect to the internet.

11/01:

The following steps were taking for troubleshooting purposes, none have worked.

Edit /etc/network/interfaces
reset network interface credentials

Edit /etc/resolv.conf
add/edit nameservers (8.8.8.8 etc.)

Edit /etc/environment (remove proxy, temp)

sudo apt-get update (no internet connection, operations fail - can not resolve/internet)

sudo apt-get update && sudo apt-get dist-upgrade

sudo dpkg --reconfigure -a

Webmin status will output that it is active but cannot find the miniserv.conf,
Virtualmin status returns ‘not installed’ or ‘missing’

Last thing to note: I am connecting via Unix/SSH on Ubuntu multi-user.target, I cannot switch to graphical.target, as the command does not initiate the gui. Therefore, I have no way of accessing the server via localhost or edit the files, and dependencies visually/manually.

What steps should I to take from here?

The server is running/active, files are not corrupted and the operating system is also not corrupted. Simply need to point the daemon to open up the network connection to reinstall and reconfigure modules etc, and resolve nameservers (primary server).

Look forward to all of your insights.

[Stegan]

I guess you didn’t take that important backup before critically uninstalling !

Can you still ping the server, is your DNS still valid.

[nivllc]

Thorough backups were made, however, the server could not ping and if there was a DNS server, it was completely misconfigured - mind you, this happened after removing an independent package [Cyrus] from the Webmin system.

[Joe]

It sounds like you removed a package that had caused other packages to be installed to satisfy dependencies, and then used autoremove, which removes all packages that are no longer needed based on dependencies. That’s a wildly dangerous thing to do on a production server without reading what autoremove is going to remove.

Since this is in the Virtualmin category, I assume you’re talking about a Virtualmin system, rather than just Webmin…so, if you removed a package that the Virtualmin metapackage depended on, it would have made a whole lot of packages become no longer depended on, and thus eligible for autoremove (because it would have removed the Virtualmin metapackage). All of this would have been in the package manager output, so always read what it says it’s going to do and what it did when it’s done.

There’s no simple solution to blowing away significant portions of the system. But, in the default configuration of dpkg, using autoremove will not remove configuration files, so you can reinstall the packages that you actually needed using apt install and their config files will still be intact (generally, though there may be quirks related to enabling services or modules in other packages if you didn’t reinstall all the same packages). But, if you purged the packages, as well, that would remove the config files with no reasonable way to recover them, short of restoring from known good backups.

I recommend either never using autoremove on a production system, or actually reading the list of packages that will be removed when you perform an autoremove. Likewise, some packages are depended on by other packages, and removing (even without an uninstall) will cause those dependent packages to be removed. Always proceed with caution when removing packages in any way, but especially autoremove, and look at what the package manager says it’s going to do and what it has done.

[nivllc]

Joe, excellent advice and useful information to note, thank you.

Removing the Cyrus software package also removed dependencies and left the system unresponsive; core configuration files were removed, or could not point to the proper directories (missing or empty files); furthermore, servers, installed or not, will not be able to resolve.

The root of the problem was not the software package or Virtualmin but Webmin and its core dependencies (server(s) in this case), not resolving due to misconfiguration.

Virtualmin could not respond despite still firing up on boot, any hosted sites will not resolve and without a DNS server, there is no root access to the default host or host:10000. Also not having access to the graphical (gui) complicated the situation, but more on that later.