[systemd-devel] [RFC] the chopping block

[Mike Gilbert]

On Wed, Feb 24, 2016 at 10:42 PM, Mike Gilbert <floppym at gentoo.org> wrote:
> 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.

Ripping systemd-initctl out of the systemd source tree was more
difficult than I anticipated. Instead, I rewrote a simpler version.
The code is on bitbucket.

https://bitbucket.org/floppym/gentoo-systemd-initctl/src