[gentoo-user] Re: sysV/openrc init script vs. systemd .service file

[Grant Edwards]

On 2014-08-11, Rich Freeman <rich0@g.o> wrote:
> On Mon, Aug 11, 2014 at 4:05 PM, Grant Edwards
><grant.b.edwards@×××××.com> wrote:
>>
>> Any advice on whether it would be easier to use a common init script
>> with sysV/OpenRC/systemd or to write a separate .service file?
>
> I'd almost certainly generate a proper unit, and not try to use a
> compatibility mode, especially if you're generating these using
> software.

It wouldn't be generated by software.  Both the sysv init script and
.service file would be maintained by hand.

> If anything it would make more sense to make a sysvinit script which
> is a wrapper for a systemd unit than the other way around.

Thanks, I'll consider that, but I'm reluctant to do so for fear of
breaking compatibility with various ancient systems in use out there.
[I can't even find hardware old enough to run some of the Linux
kernels and distro's some customers are still using.]

[...]

> Most daemons will be fairly similar to this, though a daemon which
> forks will be slightly different (type=forking, and will have a
> PIDfile setting).

The daemon is currently of the traditional forking variety with a PID
file, so it should lend itself to Type=forking PIDFile=/var/run/whatever.pid.

But, there are a number of housekeeping tasks that are performed
before starting the daemon and after terminating the daemon (checking
configuration files, verifying presence of kernel module .ko/.o files,
loading a kernel module and logging some pertinent info from that
module, unloading the kernel module, etc.).  It looks like I should
write ExecStartPre and ExecStopPost scripts for systemd to invoke.

One thing I'm still wondering about is the canonical location to
install things like ExecStartPre and ExecStopPost scripts.

I could modify the daemon to provide a "no-fork" option and then exec
it at the end of a startup script, but I don't really see much benefit
to that.

> This one is a bit fancy in that it has a post-exec script/program
> that just checks for the main service to be ready (so that reverse
> dependencies aren't started prematurely).
>
> It is important that whatever is in execstart doesn't die if this is
> a daemon.  If this is just going to modprobe something and terminate
> that is fine, but there is a slightly different way to express those
> so that it isn't considered a failure.

Thanks much for the advice.

-- 
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