Bug#1037559: systemd-networkd-wait-online waits undefinitely if no networkd managed interfaces

[Wolfgang Bumiller]

On Wed, 14 Jun 2023 22:08:41 +0800 Yangfl <mmyangfl at gmail.com> wrote:
> On Wed, 14 Jun 2023 09:42:06 +0100 Luca Boccassi <bluca at debian.org> wrote:
> > Control: tags -1 moreinfo
> >
> > On Wed, 14 Jun 2023 01:10:16 -0700 Mo <alim0x at outlook.com> wrote:
> > > Package: systemd
> > > Version: 252.6-1
> > > Severity: normal
> > > Tags: newcomer
> > > X-Debbugs-Cc: alim0x at outlook.com
> > >
> > > Dear Maintainer,
> > >
> > > after upgrade to debian 12 from debian 11, the system boots using
> > almost ~2min
> > > to prompt login.
> > >
> > > after check for systemd-analyze, get info:
> > >
> > > root at vm:~# systemd-analyze time
> > > Startup finished in 2.246s (kernel) + 2min 3.788s (userspace) = 2min
> > 6.035s
> > > graphical.target reached after 2min 3.610s in userspace.
> > >
> > > root at vm:~# systemd-analyze blame
> > > 2min 189ms systemd-networkd-wait-online.service
> > >     4.253s kdump-tools.service
> > >     1.910s apparmor.service
> > >     1.267s ifupdown-pre.service
> > >     ...
> > >
> > > in my machine there is not using systemd-networked, and no interfaces
> > managed by
> > > networkd.
> >
> > Then why is systemd-networkd-wait-online being pulled in? Did you
> > enable it or one of the targets that pull it in? If it's not in use as
> > you say, it should not run in the first place.
> >
> > --
> > Kind regards,
> > Luca Boccassi
> 
> (On behalf of alim0x at outlook.com as he is facing some network problem)
> 
> Thanks for your hint, this problem original happened in my cloud
> machine, so I checked again.

On first boot systemd uses presets (systemd.preset(5)) to configure the
enable/disable state of services. By default, systemd-networkd.service
is enabled via presets and this pulls in
systemd-networkd-wait-online.service automatically as well, while
ifupdown provides an `ifupdown-wait-online.service` alternative which
also satisfies `network-online.target`.

Given that debian defaults to ifupdown, I wonder if debian's systemd
packaging should by default set the systemd-networkd.service preset
state to disabled? (It'll only affect first boots and explicit calls to
`systemctl preset`).

In any case, container providers may want to deal with this either in
their templates or when starting up containers.
We also ran into this with bookworm templates in Proxmox VE and generate
a preset file[1] for this now to debian containers.

[1] https://git.proxmox.com/?p=pve-container.git;a=commit;h=e11806e0de064e6570d40e7c04bc4656687b2c62