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I'm just trying to understand the behavior I'm seeing. I tried adding this line to my AWS EC2's (root) crontab:

00 00 * * * shutdown -h now

But this never executed. When I added this to my own ec2-user crontab (including sudo) it did work. I've been able to run different commands from the root crontab, so why can't I run a shutdown command?

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  • I can agree that you knew when it worked for the user, since a shutdown is rather visible, but how do you know it never executed for root? Maybe it did, but there were some errors? Commented Sep 22 at 13:57
  • When you say that you unsuccessfully tried this in root’s crontab, do you mean root’s personal crontab(crontab -e) or in the system crontab at /etc/crontab? Commented Sep 22 at 16:12
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    @Kusalananda crontab -e Commented Sep 23 at 14:29
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    @decision-making-mike You were right, and I chose my words poorly when I said it "never executed". There were errors in /var/log/cron that explained the problem. Commented Sep 23 at 14:38

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I expect this is simply because shutdown isn't in cron's PATH which is just set to /usr/bin:/bin. See Where is cron's PATH set?. So try using the full path to the shutdown executable instead. On my Arch system, it's in /sbin:

$ type shutdown 
shutdown is /sbin/shutdown

So I would use:

00 00 * * * /sbin/shutdown -h now

If that still doesn't work, the way to debug this kind of thing is to redirect the command's output. So try

00 00 * * * shutdown -h now > /root/shutdown.log 2>&1

and check if there is anything in /root/shutdown.log and whether it is created. This, redirecting the command's stdout and stderr, is always the first step when debugging cron stuff.

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  • Interestingly, on my Arch today, cron's PATH is actually set to /usr/bin:/bin:/usr/sbin:/sbin which wasn't the case back in 2017. Commented Sep 22 at 14:11
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    That was it! For further supporting evidence, I saw the following in /var/log/cron: CROND[1783]: (root) CMDOUT (/bin/sh: line 1: shutdown: command not found). Commented Sep 23 at 14:37

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