Paul Wise <p...@debian.org> writes: > On Thu, Oct 18, 2018 at 5:24 AM Russ Allbery wrote:
>> Timer units are also a more complicated problem since they're not a >> superset of cron behavior. They do some things better than cron jobs; >> they do other things much *worse* than cron jobs. I have cron jobs >> that I wanted to convert to timer units and discovered I couldn't >> because timers simply wouldn't work for what I was trying to do. > Could you give some examples of the issues you discovered with systemd > timers? > BTW, we have in systemd-cron a tool for generating systemd units from > crontab/etc. MAILTO was the main thing that I remember missing in terms of pure functionality. The other problem I can recall wasn't functionality, but was ease of use: a timer unit can only trigger a service unit, and service units aren't suitable for doing arbitrary shell scripting. Here, this wasn't for packaging but was instead as a local system administrator. I have a lot of cases where I drop a simple 20-line shell script into /etc/cron.daily that has some logic intermixed with variables that list things like, say, directories to back up to another host. I looked at replacing that with a timer unit, just as an experiment, but I would have had to write the timer unit to control the timing, a separate exec unit that specifies what command to run, and then put the shell script into yet a third file (with no particularly obvious location for the local system administrator). Since I don't like using /usr/local/bin for such things, I'd probably end up extracting configuration from the script, sticking the script in a local Debian package, and installing the configuration separately. I now have four different files just to replace a single file dropped into a directory. Admittedly, this was to replace something run from cron.daily, and maybe the solution there (if one is considering a system that doesn't need a separate cron daemon, which in theory should be possible if one wanted to do it although not necessary of course) would be to have a single timer unit that uses run-parts the way that cron runs cron.daily. Timer units were a closer match for cron.d, although I'm still missing MAILTO. -- Russ Allbery (r...@debian.org) <http://www.eyrie.org/~eagle/>
