Running script in crontab--reboot: command not found

Question

I've set a script in my root crontab that is supposed to restart my machine with the reboot command.

However, I am getting a reboot: command not found despite the fact that reboot is in the root user's path.

$ sudo su
$ which reboot
/sbin/reboot
$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin

---

My script:

#!/bin/bash

ping 8.8.8.8 -c 1 > /dev/null 2>&1; exit_code=$?
time_stamp=$(date +"%Y%m%d-%H%M")

if [ $exit_code -ne 0 ]; then
    (1>&2 echo "$time_stamp: failed with exit code $exit_code; restarting now")
    reboot
else
    echo "$time_stamp: ok"
fi

---

root user crontab:

$ sudo crontab -l
58 * * * * /home/pi/github/ping-restart/ping-restart.sh >> /home/pi/github/ping-restart/cron.log 2>&1
$ sudo su
58 * * * * /home/pi/github/ping-restart/ping-restart.sh >> /home/pi/github/ping-restart/cron.log 2>&1

---

...yes, this is only a temporary workaround while I figure out why the internet keeps dropping.

Holocaine

Maybe try using the absolute path /sbin/reboot... – Rasping

@l'L'l This seems to work. A script with which reboot in crontab has no output (indicating not found), while which /sbin/reboot has the output /sbin/reboot, as expected. Any idea why reboot by itself does not work? – Holocaine

Because cron has no clue of where the reboot command is, so you have to give the location. In cron only certain commands can be called using just the name, so often you need to give it the absolute path. – Rasping

@l'L'l: I'm not sure I understand. I'm able to use other scripts in the root user crontab that has commands that are called by name instead of their full path (date as in /bin/date, basename as in /usr/bin/basename,traceroute as in /usr/sbin/traceroute). What's so special about reboot? – Holocaine

See Gordon's answer... – Rasping

Answer 1

cron jobs run with a very basic environment setup; among other things, the default PATH is just /usr/bin:/bin. It does not use the user's regular shell setup. There are several ways to solve this:

• Use the full path in the script (i.e. /sbin/reboot).
• Set PATH in the script before using reboot (i.e. PATH=/usr/bin:/bin:/usr/sbin:/sbin).
• Set PATH in the crontab before the entry for your script (syntax is the same as in the script).

Dishman

This seems 100% to be what's happening. Verified it too, setting echo $PATH > cron_path_log as a job. – Holocaine