Bug#940034: libelogind0: replacing a core system library and conflicting against the default init considered harmful

[Mark Hindley]

Julien,

On Fri, Sep 27, 2019 at 03:39:43PM +0200, Julien Cristau wrote:
> So one thing I think we should ensure is we don't end up uninstalling
> systemd without an explicit user choice.
> 
> The "init" package has the "Important: yes" control field which as I
> understand it tells apt to behave like "Essential: yes", except for not
> trying to install the package if it is not installed.
> 
> That's not quite enough for our purposes, because apt would still be
> allowed to replace systemd-sysv with sysvinit-core, but maybe
> systemd-sysv could get that flag as well?
> 
> Julian didn't seem to find the idea crazy when we brought that up on
> irc.

Thanks. The aim of preventing accidental removal of systemd is very
reasonable. However, using this approach the hurdle you create even to a user
who really wants to uninstall is pretty high. Few people will continue having
seen the 'You are about to do something potentially harmful' warning.

I think the effect we are after is rather closer to that of apt-mark hold
systemd or dpkg --set-selections systemd hold. Once held, uninstalling the
package requires a specific request to apt.  But I realise this approach will
also prevent upgrades.

Mark