[systemd-devel] Nested systemd

[Mantas Mikulėnas]

On Mon, Dec 11, 2017 at 10:14 PM, Boyce, Kevin P [US] (AS) <
Kevin.Boyce at ngc.com> wrote:

> Good Afternoon List,
>
>
>
> I have a question regarding the use of systemd.  I would like to know if
> it is possible to have two instances of system running at a time?
>
>
>
> For instance I have an application that has a very complicated set of
> startup procedures.  It runs on linux.  I was considering using an instance
> of systemd with some custom unit files and targets as a self-contained
> startup procedure.  I was wondering if systemd could then start this
> systemd instance using an alternate root directory?
>

Your description sounds almost exactly like what containers
(systemd-nspawn, LXC, Docker) are normally used for – including both the
nested init system and the alternate root directory. Systemd should work
just fine when used as a container init process.

But beyond that, systemd only supports *one* "system mode" instance per
system – that is, PID 1.

(It *does* support unprivileged "user mode" instances of `systemd --user`,
limited to one per UID, but I'm not sure if these are suitable for
"complicated startup procedures" in your case.)

-- 
Mantas Mikulėnas <grawity at gmail.com>
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