Temporary failure in name resolution on Ubuntu server 22.04.3 LTS

[Oliver Grawert]

Hi,
Am Dienstag, dem 28.11.2023 um 12:04 +0100 schrieb Bo Berglund:
> 
> I think that the crucial upgrade was the 16 -> 18 one where the
> network-manager
> should have been introduced, right? But wasn't...

right, i assume the same here, though you are mixing things up,
network-manager is the tool for managing networks on desktop installs,
it has never been shipped on servers. server and cloud use systemd-
networkd (and for name resolution its companion systemd-resolved) 

in earlier times network-manager used resolvconf and dnsmasq for name
resolution (one forwarding to the other) while servers used ifupdown
for network device management and resolvconf for name resolution.

since managing devices with systemd-networkd isnt super intuitive and
ubuntu needed network management for cloud images too netplan was
introduced as a top-level management tool that integrates well with the
cloud management bits. so on server you use netplan as the frontend
config tool and systemd-networkd along with systemd-resolved as the
backends doing the actual management.

on the desktop netplan can actually manage network-manager since 22.04
so the same configuration can be used across all ubuntu installs (i.e.
netplan can be used for automated and pre-configured desktop installs
this way without having to explicitly tinker with network-manager
configs)...

so your server misses the netplan configuration, not network-manager ;)

> 
> So my question now is if I can just sudo apt install network-manager
> on the
> Ubuntu 20.04 server in the office and it will migrate whatever
> network settings
> there are to itself?

you already have netplan installed on your server (as your package list
above showed) and you do not want network-manager there at all.

there are corner cases where one would probably want network-manager on
server installs, i.e. for a wifi-only based server or when your server
does connect via any mobile connection, but on standard servers you
want netplan and systemd-networkd.

the upgrade to 18.04 should have migrated your configs from
/etc/network/interfaces (used by ifupdown) to a proper
/etc/netplan/default.yaml, this did not happen ... 

 
> 
> I.e. can I do this install remotely via ssh?
> 

to do this by hand you'd have to manually create a netplan yaml file
and transfer your old configs into it, then remove ifupdown and
resolvconf and make sure systemd-networkd and systemd-resolved are
installed. while an experienced admin could probably do that via ssh, i
wouldnt really :) there is quite some risk that you mess it up and lock
yourself out.  


if i were you, i'd add some temporary hack to mangle the resolvconf
stuff ... i.e. to add your 8.8.8.8 entry from /etc/rc.local to the
config on every boot or use /etc/resolvconf.d snippets or whatnot for
the time being to solve the immediate issue...

... then take time to familarize with:

https://netplan.readthedocs.io/en/stable/

and eventually go to the office with enough dedicated time to make the
manual transition described above ... (if your local server at home has
netplan configs already you can surely also take a look there)

ciao
	oli
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: This is a digitally signed message part
URL: <https://lists.ubuntu.com/archives/ubuntu-users/attachments/20231128/34c3ce2b/attachment.sig>