Re: How to make systemd unit files work in all supported distros?

[Nathan Cutler <ncutler@suse.cz>]

On 02/08/2016 11:55 PM, Ken Dreyer wrote:
> Which executables are different? Fedora's pretty flexible about this;
> I'm sure we could ship ceph-disk in /usr/bin if it lets us align with
> SUSE or whatever.

Here's another one:

https://github.com/ceph/ceph/blob/master/systemd/ceph-osd%40.service#L13

%{_libexecdir} expands to /usr/lib on SUSE :-(

And "sh -c" would not help us here, either.

> On Mon, Feb 8, 2016 at 2:44 AM, Nathan Cutler <ncutler@suse.cz> wrote:
>> In master we currently have an issue with the systemd unit files in that
>> they contain hard-coded paths that are specific to RH/CentOS/Fedora. Other
>> distros can and do have the executables in different places.
>>
>> I opened a bug[1] for this, but before I go off trying to fix it I would
>> like to solicit your feedback on the following possible approaches I came up
>> with (and/or "turn me on" to a different approach):
>>
>> (1) Rely on PATH. Basically, instead of running executables directly, run
>> them by "/bin/sh -c", which summons the system PATH to help find the
>> executables. See https://github.com/ceph/ceph/pull/6803 for an example of
>> this.
>>
>> (2) Set environment variables in /etc/sysconfig/ceph. Systemd has an
>> EnvironmentFile directive which reads environment variables from a file. If
>> this were pointed to /etc/sysconfig/ceph (as it is in several unit files
>> already), we could set the distro-specific parts of the paths there and
>> write the paths similar to how we do it in the spec file.
>>
>> (3) Generate unit files at build time. In this approach, the unit files
>> would exist in the source tree as templates (e.g. ceph-osd@.service.in) and
>> these would get transformed into the "real" unit files at build time. The
>> ceph-detect-init utility could be used to determine the distro and the
>> Makefile logic would then fill in the templates as needed for the distro.
>>
>> Of these three approaches, only (3) would seem to be general enough to work
>> nicely for all distros. (For example, EnvironmentFile will need to be set to
>> /etc/default/ceph on Debianesque systems and there is no obvious way to set
>> *this* path as an environment variable.)
>>
>> Any thoughts on this? Thanks in advance!
>>
>> [1] http://tracker.ceph.com/issues/14687
>>
>> --
>> Nathan Cutler
>> Software Engineer Distributed Storage
>> SUSE LINUX, s.r.o.
>> Tel.: +420 284 084 037
>> --
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-- 
Nathan Cutler
Software Engineer Distributed Storage
SUSE LINUX, s.r.o.
Tel.: +420 284 084 037