Menu
Please consider following crontab (root):
SHELL=/bin/bash
...
...
0 */3 * * * /var/maintenance/raid.sh
And the bash script /var/maintenance/raid.sh:
#!/bin/bash
echo -n "Checking /dev/md0... "
if ! [ $(mdadm --detail /dev/md0 | grep -c "active sync") -eq 2 ]; then
mdadm --detail /dev/md0 | mail -s "Raid problem /dev/md0" "[email protected]";
echo "ERROR"
else
echo "ALL OK"
fi;
#-------------------------------------------------------
echo -n "Checking /dev/md1... "
...
And this is what happen when...
...executed from shell prompt (bash):
Mail with mdadm --detail /dev/md0 output is sent to my email (proper behaviour)
...executed by cron:
Blank mail is sent to my email (subject is there, but there is no message)
Why such difference and how to fix it?
509
Sourcing a script will run the commands in the current shell process. Changes to the environment take effect in the current shell. Executing a script will run the commands in a new shell process.
Cron Uses /bin/sh By Default, Not Bash Bash ( /bin/bash ) is a common shell on most distros, and is an implementation of sh. The /bin/sh file is a symlink to an sh implementation, but it isn't always bash. On Debian based systems like Ubuntu, and on macOS, /bin/sh links to dash by default.
It is a wildcard for every part of the cron schedule expression. So * * * * * means every minute of every hour of every day of every month and every day of the week .
To check to see if the cron daemon is running, search the running processes with the ps command. The cron daemon's command will show up in the output as crond. The entry in this output for grep crond can be ignored but the other entry for crond can be seen running as root. This shows that the cron daemon is running.
As indicated in the comments, do use full paths on crontab scripts, because crontab does have different environment variables than the normal user (root in this case).
In your case, instead of mdadm, /sbin/mdadm makes it.
How to get the full path of a command? Using the command command -v:
$ command -v rm
/bin/rm
cron tasks run in a shell that is started without your login scripts being run, which set up paths, environment variables etc.
When building cron tasks, prefer things like absolute paths and explicit options etc
32
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
