[systemd-devel] Antw: Re: Antw: [EXT] Re: Q: Start network in chroot?

[Andrei Borzenkov]

On 14.06.2022 08:57, Ulrich Windl wrote:
>>>> Colin Guthrie <gmane at colin.guthr.ie> schrieb am 13.06.2022 um 16:34 in
> Nachricht <t87hth$49u$1 at ciao.gmane.io>:
> 
>> Ulrich Windl wrote on 13/06/2022 14:42:
>>>>>> Colin Guthrie <gmane at colin.guthr.ie> schrieb am 13.06.2022 um 14:58 in
>>> Nachricht <t87c9t$lon$1 at ciao.gmane.io>:
>>>> Ulrich Windl wrote on 13/06/2022 09:09:
>>>>> Hi!
>>>>>
>>>>> Two questions:
>>>>> 1) Why can't I use "systemctl start network" in a chroot environment (e.g.
>>>> mounting the system from a rescue medium to fix a defective kernel)? When I
>>>> try I get: "Running in chroot, ignoring command 'start'"
>>>>> 2) How can I start the network using systemd?
>>>>
>>>> You may wish to consider "booting" the container rather than just chrooting.
>>>
>>> No container involved; an unbootable system instead, and I'd like to have 
>> networking available for repair.
>>> So obviously I cannot boot. Without systemd it wouldn't be a problem.
>>
>> So you're not running an init system but you want the (not-running) init 
>> system to run something for you?
> 
> I don't understand:
> The rescue system I'm using (SLES 14 SP3) uses systemd, and the system that woon't boo is also using systemd (SLES15 SP3).
> 
>>
>> If you're wanting to repair a system, and you need networking then bring 
>> up the network in the repair image before chrooting surely? (i.e. what 
>> Mantas said)
> 
> Well the configuration files are not in the generic rescue system, but in the system that won't boot (I think I had explained that).
> Also things became much more complicated with systemd and wickedd and all that stuff.
> 
>>
>> If you want to run the network inside the (broken) system you're trying 
>> to repair, then just run the networking scripts or program manually. 
>> i.e. run whatever /etc/init.d/network says or whatever ExecStart= says 
>> in /usr/lib/systemd/network.service says (paths may vary).
> 
> There are no files inside /etc/init.d/.
> 
>>
>> There will be loads of other stuff that the init system does that won't 
>> be in place (e.g. tmpfiles, etc.) which you may or may not need to setup 
>> manually too, but you can likely get it running.
>>
>>  > Without systemd it wouldn't be a problem.
>>

Of course it would for anything that goes beyond simple "ip address add".

>> Sure when "init" was just a bundle of scripts, you could run one of the 
>> scripts it runs and hope for the best. You can generally still do that, 
>> but just don't expect asking a non-running program to do it for you to work!
> 
> Still I don't understand: systemd is running.
> 

I do not understand what you do not understand. systemd is running in
your rescue system, not in chroot. You want to tell this systemd to use
configuration inside chroot, but systemd is rescue system is not aware
of it. It cannot be done unless you start systemd inside of chroot as
service manager.

And wicked, systemd-networkd, NetwormManager all need functional D-Bus.
D-Bus is again outside of your chroot with the same caveats. Even
without systemd in the mix it would be a problem.

You have already been told several times - start your networking in
rescue system before doing chroot. Or use something like systemd-nspawn
instead of chroot.