5 ms·

Not that I have a problem with systemd, which I don't hate and I use extensively (both in my customers' products and on my machine because it's the default init

by alxlaz 7y ago

Not that I have a problem with systemd, which I don't hate and I use extensively (both in my customers' products and on my machine because it's the default init system of the distro I use), but this thread illustrates a lot of why a lot of pre-systemd Linux users just don't dig it. Every time someone asks "why should I use systemd instead of cron" they get these (technically correct -- the best kind of correct!) answers about how systemd timers allow you to attach jobs to cgroups, define dependencies, test unit files separately vs. changing crontabs for 1 minute ahead (which I don't think is a "cron idiom" -- I've certainly never done i -- but we all have our weird hacks), and how it has built-in jitter options and per-job environment settings and whatnot. These are all very relevant for real-life workloads of super advanced cloud systems, I'm sure. (Which I'm not saying in a derogatory way. I haven't written back-end code in like 12 years now, the things that are happening there today blow my mind. I know these are complex systems so I'm pretty sure they have complex problems which have complex solutions.) But guys, I just need to run a bash script every day at 2 AM. 99% of us just need to run a bash script every day at 2 AM. This has worked reliably in cron since practically forever. I have grumpily learned the new way of doing it but I can't really justify the time I've put into it, nor the (very extensive) troubleshooting that was involved in it. I just woke up one morning and sat down in front of a Linux machine and I found out that there's a new way to run things at 2 AM. If you want to woo me with cool systemd-timers features, tell me that it finally has an equivalent to cron's MAILTO, so that I don't have to write yet another systemd unit file that wraps a script written by me if I want to get a notification when a job has failed, because somehow that hasn't made its way into the "everything but the kitchen sink" list which otherwise includes things like attaching jobs to cgroups.

yrro 7y ago
I suppose it would be quite nice to have a MailTo= directive in a service. When the service stops, systemd could retrieve whatever it logged to the journal and mail it to the specified address. Until such a feature is implemented, you could try: ExecStart=/bin/bash -c 'shopt -o pipefail; mycommand | mail -s foo@example.com' Certainly not as convenient as MailTo=, but a lot less complicated than using OnFailure= with a separate service that tries to mail you the output.
- alxlaz 7y ago
  Huh. I never thought of that, although it was so damn obvious (I feel twice as stupid now that I realize I do a version of that on my machine, albeit not in order to send mail). I guess that's what I get for going all "Arch Wiki will you please just show me how you kids are doing it today and leave me be" on it. But to be honest, not having to do <shell> -c <exec this or send me an email> ever again is one of the reasons why we're doing the whole systemd thing, and one of its big promises. If it comes to writing shell mantras again, I might as well use vixie cron (or one of its descendants) and benefit from 30+ years of bugfixes across more Unices than I can name, plus the acquired wisdom of the Interwebs. Edit: plus... does this still allow you to get the other goodies, like being able to specify environment variables for a specific job?
  - yrro 7y ago
    Not sure I follow about the environment variables. As for 'exec this or send me an email' -- I would also much prefer to see this be done by systemd itself. Fortunately bash's 'pipefail' feature plus bsd-mailx's '-s' flag make this reasonably quick and sane; I wouldn't even bother to attempt it if I were stuck with POSIX sh or if the mail command lacked the logic to not send the mail if stdin is empty.
    - alxlaz 7y ago
      > Not sure I follow about the environment variables. I thought that environment variable passed via the Environment= options might not be correctly set, but it seems they are :-).
quleap 7y ago
Try systemd-cron https://github.com/systemd-cron/systemd-cron https://github.com/systemd-cron/systemd-cron. Best of both worlds: simplicity of crontab and manageability of systemd. And it comes with built-in MAILTO support.
JetSpiegel 7y ago
You can use systemd-run with the --calendar option for one-off timers, it even supports the cron syntax.

by alxlaz 7y ago

yrro 7y ago

I suppose it would be quite nice to have a MailTo= directive in a service. When the service stops, systemd could retrieve whatever it logged to the journal and mail it to the specified address. Until such a feature is implemented, you could try: ExecStart=/bin/bash -c 'shopt -o pipefail; mycommand | mail -s foo@example.com' Certainly not as convenient as MailTo=, but a lot less complicated than using OnFailure= with a separate service that tries to mail you the output.

alxlaz 7y ago
Huh. I never thought of that, although it was so damn obvious (I feel twice as stupid now that I realize I do a version of that on my machine, albeit not in order to send mail). I guess that's what I get for going all "Arch Wiki will you please just show me how you kids are doing it today and leave me be" on it. But to be honest, not having to do <shell> -c <exec this or send me an email> ever again is one of the reasons why we're doing the whole systemd thing, and one of its big promises. If it comes to writing shell mantras again, I might as well use vixie cron (or one of its descendants) and benefit from 30+ years of bugfixes across more Unices than I can name, plus the acquired wisdom of the Interwebs. Edit: plus... does this still allow you to get the other goodies, like being able to specify environment variables for a specific job?
- yrro 7y ago
  Not sure I follow about the environment variables. As for 'exec this or send me an email' -- I would also much prefer to see this be done by systemd itself. Fortunately bash's 'pipefail' feature plus bsd-mailx's '-s' flag make this reasonably quick and sane; I wouldn't even bother to attempt it if I were stuck with POSIX sh or if the mail command lacked the logic to not send the mail if stdin is empty.
  - alxlaz 7y ago
    > Not sure I follow about the environment variables. I thought that environment variable passed via the Environment= options might not be correctly set, but it seems they are :-).

quleap 7y ago

Try systemd-cron https://github.com/systemd-cron/systemd-cron https://github.com/systemd-cron/systemd-cron. Best of both worlds: simplicity of crontab and manageability of systemd. And it comes with built-in MAILTO support.

JetSpiegel 7y ago

You can use systemd-run with the --calendar option for one-off timers, it even supports the cron syntax.