1

I have seen a lot of times (1, 2 )this question, but I didn't find the answer, so here I go.

I'm running Debian 11, but I guess it works the same for any Debian-like distro.

My crontab -e looks like:

...
@reboot sleep 20 && /opt/isPromscaleOnOrOff.sh
...

And the content of isPromscaleOnOrOff.sh:

#!/bin/bash

SERVICE="promscale"
if pgrep -x "$SERVICE" >/dev/null
then
    echo "$SERVICE is running"
else
    echo "$SERVICE is stopped, I will run it now"
    nohup promscale --db-name asdf1234--db-password asdf1234 --db-user asdf1234 --db-ssl-mode allow --install-extensions & >> /dev/null
    disown
fi

But when I restart the VM the script isn't runing, tho the cron logs in /var/log/syslog show the crontab starting the script.

What I wanna achieve can be easilly done daemonizing the process (wich I indeed did), I just wanna know why crontab doesn't start up my script.

Improve this question
9
  • On the one hand, you say the log shows cron running the script; on the other, you say it isn't running. In the end, we can't tell what's happening because you don't show any logs or what happens at all. Commented Oct 19, 2021 at 21:23
  • Obvious question: the script has execute permission set? Commented Oct 19, 2021 at 21:25
  • See unix.stackexchange.com/tags/cron/info for common cron-related errors. My guess is that promscale isn't in the PATH. Commented Oct 19, 2021 at 21:31
  • Take user as the login id for the user that owns this job. What recent errors are in the mailbox file /var/mail/user? (If it exists it will be readable as a plain text file.) Commented Oct 19, 2021 at 21:48
  • 1
    "I know the script isn't runing because it would start the promscale service, wich it doesn't" that's false logic. All you know is that the service didn't start. You don't know whether or not your cron attempted to start it, because you haven't recorded that the script ran. Commented Oct 19, 2021 at 22:04

1 Answer 1

Reset to default
4

Jobs run through cron aren't run in the same runtime environment that you have on your desktop. None of your PATH changes, or other environment variable settings from ~/.bashrc are automatically propagated to your cron job. For example, there's no $DISPLAY, so GUI programs need special treatment (read man xhost).

One can set environment variables for all one's cron jobs in the crontab file Read man 5 crontab.

Look at the results of echo "=== id ===";id;echo "=== set ===";set;echo "=== env ===";env | sort;echo "=== alias ===";alias in each of your environments.

Since the command part of the crontab line is, by default, interpreted by /bin/sh, which has a simpler syntax than /bin/bash, I recommend having command be a call to a bash script (executable, mounted, starts with #!/bin/bash) which sets up the environment, then calls the desired program.

Improve this answer

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.