[systemd-devel] [RFC] the chopping block

[Mike Gilbert]

On Fri, Feb 19, 2016 at 7:22 AM, Lennart Poettering
<lennart at poettering.net> wrote:
> On Thu, 18.02.16 20:33, Mike Gilbert (floppym at gentoo.org) wrote:
>
>> On Thu, Feb 11, 2016 at 12:06 PM, Lennart Poettering
>> <lennart at poettering.net> wrote:
>> > 1) systemd-initctl (i.e. the /dev/initctl SysV compat support). Last
>> >    time Debian was still using that, maybe this changed now?
>>
>> Gentoo allows switching between systemd and openrc (sysvinit) at boot
>> time, and will continue to do so for the foreseeable future.
>>
>> By default, sysvinit owns /sbin/initctl, /sbin/halt, etc. Users may
>> swap these to symlinks to systemd and systemctl by setting a USE flag,
>> but if they do so they knowingly lose the ability to switch back to
>> openrc without a rebuild of the affected packages.
>>
>> I would like to selfishly request that you keep this interface around
>> as long as possible; if you remove it I will have to come up with some
>> replacement.
>
> So here's probably what is going to happen.
>
> The initctl support in systemctl will be dropped and replaced by some
> callout script support. i.e. when you want to use systemctl to reboot
> a sysvinit system, then systemctl won't do that anymore, but it will
> invoke some shell script as a fallback, where distros can place the
> necessary commands if they care about this. This follows how we do
> sysv script enable/disable handling (i.e. the chkconfig hookup).
>
> We'll eventually kill /dev/initctl support. Distros should really find
> their own replacement for this. They can either take the current code,
> build it externally, or write some new code. You might be able to
> implement this in a carefully prepared shell script that invokes
> busctl to do the reboot. You could use "dd" to read the initreq
> structure from STDIN with the precise size, then figure out which kind
> of request it is (again, by using dd to extract the four bytes
> starting at index 4 of that request structure) and then simply execute
> the right busctl command to poweroff/reboot/...
>
> I'll not drop this right-away, but let's say in 6month or so this will
> go away. This should be an ample heads-up to find a replacement and
> prepare for this.

The existing systemd-initctl (/dev/initctl) interface works quite
nicely, so I will probably end up extracting it from systemd when you
drop it, or just building/installing it from an older systemd tarball.
No need to reinvent the wheel.

Thanks for the response.