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Re: Questions about packaging systemd unit files

On Sun, Aug 05, 2018 at 10:20:38PM +0100, Simon McVittie wrote:
> On Sun, 05 Aug 2018 at 16:52:46 -0400, Theodore Y. Ts'o wrote:
> > 1) Am I right in understanding that after modifying or adding any
> >    systemd unit or timer files, I must run "systemctl daemon-reload"?
> Yes, but preferably via dh_installinit (if you also have a corresponding
> LSB/sysvinit script, like most daemons) or dh_installsystemd (if not,
> like e.g. systemd-cron or quake4-server) rather than directly.

There's a comment in the dh_installinit man page:

  dh_installinit is a debhelper program that is responsible for
  installing init scripts with associated defaults files.  In
  compatibility levels up to 11, dh_installinit also handled upstart
  job files and systemd service files.

I realize that compat level 11 is the recommended, and since level 12
is still open for development, but it sounds like in the future level
12 isn't going to do automatically handle init scripts automatically?

One of the reasons why I hadn't considered using dh_installinit or
dh_installsystemd is because the patches submitted upstream for
e2scrub[1] currently install the systemd unit as part of Makefile
rules.  I could move them out of Makefile install rules into the
debian directory, but that would be kind of a pain, and would mean
trying to keep the files in the debian directory in sync with the ones
in the upstream source directory.

[1] This is a script to do on-line, background scrubbing of ext4 file
systems to looking for file system problems.

Also, for a package which is either essential or required, using
debhelper commands in the maintainer scripts would mean adding a
dependency, which would mean what is currently an "optional" package
would end up getting dragged in automatically.  Is this acceptable?  I
would think it might be considered undesirable.

Finally, if I have a systemd timer file, as well as a crontab entry,
what is the recommended way to decide whether to install/use the
crontab versus the timer unit file?  Should package maintainers try to
use systemd timer files at all, given that complexity and the fact
that the right thign won't happen on sysvinit-only systems at all?

I've never been a fan of systemd, but it's what Debian is chosen, and
my intention is to provide first class support for systemd.  What's
not clear to me how much support are maintainers obliged to give for
non-systemd installations, and what's considered best practices for
supporting them.

For example, we could say that timer files are strongly discouraged
and everyone MUST use crontab entries.  Or we could say that on
systemd systems, the cron package may not exist and crontab entries
are now deprecated.  Or we could say that package maintainers must try
their best to support both.

There's nothing in Debian Policy to give guidance, and I suspect it's
too early for that.  Any suggestions though would be appreciated.

    	      	     	 	     	    - Ted