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

[Rich Freeman <rich0@gentoo.org>]

On Mon, Aug 11, 2014 at 4:05 PM, Grant Edwards
<grant.b.edwards@gmail.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.  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.

Sysvinit scripts are just that - touring-complete scripts.

Systemd units are declarative.

Here is the Gentoo mysqld unit, which is pretty simple:

[Unit]
Description=MySQL database server
After=syslog.target
After=network.target

[Service]
Type=simple
User=mysql
Group=mysql

# Note: we set --basedir to prevent probes that might trigger SELinux alarms,
# https://bugzilla.redhat.com/show_bug.cgi?id=547485
ExecStart=/usr/bin/mysqld_safe --basedir=/usr
ExecStartPost=/usr/libexec/mysqld-wait-ready $MAINPID

# Give a reasonable amount of time for the server to start up/shut down
TimeoutSec=300

# We rely on systemd, not mysqld_safe, to restart mysqld if it dies
Restart=always

# Place temp files in a secure directory, not /tmp
PrivateTmp=true

[Install]
WantedBy=multi-user.target

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).  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.

Rich