Re: Installing an Alternative Init?
On Sat 15 Nov 2014 at 19:31:27 -0500, The Wanderer wrote:
> On 11/15/2014 at 07:21 PM, Paul E Condon wrote:
>
> > Yet another topic: It should be possible to install systemd on a
> > system that already has some other init system installed on it. This
> > should be tested, but how?
>
> If I understand what you mean by "install systemd", then it's trivial:
>
> apt-get install systemd
>
> That does not switch the active init system to be systemd. Doing *that*
> would require:
>
> apt-get install systemd-sysv
>
> and even that, in its turn, does not (automatically?) remove
> sysvinit-core from the system; you can still boot to it (from a
> backup-installed location) with a kernel command line option, as a
> fallback if systemd does break something too badly to even boot.
systemd-sysv and sysvinit-core are not co-installable and this is
expressed in the Conflicts: for both packages. Installing one results
in the other being removed.
> Or that's the claim, anyway. I've been examining files from
> sysvinit-core on my own computer in an attempt to remind myself of some
> of the details of how that works, and at a glance I don't see the backup
> copy of /sbin/init anywhere...
A Wheezy system has the sysvinit package installed. Moving to Jessie
will upgrade this package. The only thing of real interest in it is
/lib/sysvinit/init, the fallback SysV init binary.
A new installation does not have the sysvinit package so it would have
to be purposefully installed to get the fallback init.
Which leads to yet another way of getting a first boot with sysvinit
using d-i:
1. Preseed installation of sysvinit with base-installer/includes or a
late_command.
2. Boot with 'init=/lib/sysvinit/init'. A late_command could put this in
/etc/default/grub.
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