crontab’s @reboot only works for root?

man 5 crontab is pretty clear on how to use crontab to run a script on boot:

   These special time specification "nicknames" are supported, which replace the 5 initial time and date
   fields, and are prefixed by the `@` character:
   @reboot    :    Run once after reboot.

So I happily added a single line to my crontab (under my user account, not root):

@reboot     /home/me/myscript.sh

But for some reason, myscript.sh wouldn’t run on machine reboot.
(it runs fine if I invoke it from the command line, so it’s not a permissions problem)

What am I missing?

Update to answer @Anthon’s questions:

1. Oracle-linux version: 5.8 (uname: 2.6.32-300.39.2.el5uek #1 SMP)
2. Cron version: vixie-cron-4.1-81.el5.x86_64
3. Yes, /home is a mounted partition. Looks like this is the problem. How do I workaround this?
4. Currently, myscript.sh only echos a text message to a file in /home/me.

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

This can be a bit of a confusing topic because there are different implementations of cron. Also there were several bugs that broke this feature, and there are also some use cases where it simply won’t work, specifically if you do a shutdown/boot vs. a reboot.

Bugs

datapoint #1

One such bug in Debian is covered here, titled: cron: @reboot jobs are not run. This seems to have made it’s way into Ubuntu as well, which I can’t confirm directly.

datapoint #2

Evidence of the bug in Ubuntu would seem to be confirmed here in this SO Q&A titled: @reboot cronjob not executing.

excerpt

comment #1: …. 3) your version of crond may not support @reboot are you using vix’s crond? … show results of crontab -l -u user

comment #2: … It might be a good idea to set it up as an init script instead of relying on a specific version of cron’s @reboot.

comment #3: … @MarkRoberts removed the reboot and modified the 1 * * * * , to */1 * * * * , problem is solved! Where do I send the rep pts Mark? Thank you!

The accepted answer in that Q&A also had this comment:

Seems to me Lubuntu doesn’t support the @Reboot Cron syntax.

Additional evidence

datapoint #3

As additional evidence there was this thread that someone was attempting the very same thing and getting frustrated that it didn’t work. It’s titled: Thread: Cron – @reboot jobs not working.

excerpt

Re: Cron – @reboot jobs not working

Quote Originally Posted by ceallred View Post
This is killing me… Tried the wrapper script. Running manually generates the log file… rebooting and the job doesn’t run or create log file.

Syslog shows that CRON ran the job… but again, no output and the process isn’t running.
Jul 15 20:07:45 RavenWing cron[1026]: (CRON) INFO (Running @reboot jobs)
Jul 15 20:07:45 RavenWing CRON[1053]: (ceallred) CMD (/home/ceallred/Scripts/run_spideroak.sh > /home/ceallred/Scripts/SpiderOak.log 2>&1 &)

It’s seems like cron doesn’t like the @reboot command…. Any other ideas?

Okay… Partially solved. I’ll mark this one as solved and start a new thread with the new issue…..

I think the answer was my encrypted home directory wasn’t mounted when CRON was trying to run the script (stored in /home/username/scripts). Moved to /usr/scripts and the job runs as expected.

So now it appears to be a spideroak issue. Process starts, but by the time the boot process is finished, it’s gone. I’m guessing a crash for some reason…. New thread to ask about that.

Thanks for all the help!

Once this above user figured out his issue he was able to get @reboot working out of the crontab entry of a user.

I’m not entirely sure what version of cron is used on Ubuntu, but this would seem to indicate that user’s can use @reboot too, or that the bug was fixed at some point in subsequent versions of cron.

datapoint #4

I tested on CentOS 6 the following and it worked.

Example

$ crontab -l
@reboot echo "hi" > /home/sam/reboot.txt 2>&1

I then rebooted the system.

$ sudo reboot

After the reboot.

$ cat reboot.txt 
hi

Take aways

1. This feature does seem to be supported for both system and user crontab entries.
2. You have to make sure that it’s supported/working in your particular distro and/or version of the cron package.

For more on how the actual mechanism works for @reboot I did come across this blog post which discusses the innards. It’s titled: @reboot – explaining simple cron magic.

Debugging crond

You can turn up the verbosity of crond by adding the following to this configuration file on RHEL/CentOS/Fedora based distros.

$ more crond 
# Settings for the CRON daemon.
# CRONDARGS= :  any extra command-line startup arguments for crond
CRONDARGS="-L 2"

The valid levels are 0, 1, or 2. To revert this file back to it’s default logging level simply remove the "-L 2" when you’re done debugging the situation.

Method 2

I found out that on my Ubuntu machine, I do not have access to dns services, yet, at @reboot time. This prevented me from mounting remote volumes. This corny, yet simple, solution worked:

@reboot sleep 60 && /home/me/bin/mount.sh 2>&1 >> /home/me/reboot.log

(in root cron; last parts only for debugging)

Method 3

I have mac osx as well and I had same issue where my script were not running. but When i fixed my script to like

@reboot   cd /home/me/  && sh myscript.sh

it worked fine for me. make sure to make your shell file to be executable by running the command

chmod +x myscript.sh

Method 4

I don’t know if you have already solved this, or if any of the above was the solution you needed, but another possibility is:

if you have your /home directory encrypted, it may not be available until you log in, i.e. it is not available at reboot.

in this scenario, you could move your scripts to another location like /srv or /opt or /usr/local/bin/ etc.

Method 5

Take a fresh install of Ubuntu Gnome 13.10 (default user in my case: avanderneut).

<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="513027303f3534233f342425112436363e">[email protected]</a>:~$ crontab -l
no crontab for avanderneut
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="026374636c6667706c677776427765656d">[email protected]</a>:~$ crontab -e
no crontab for avanderneut - using an empty one

Select an editor.  To change later, run 'select-editor'.
  1. /bin/ed
  2. /bin/nano        <---- easiest
  3. /usr/bin/vim.tiny

Choose 1-3 [2]: 3
crontab: installing new crontab
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e38295828d8786918d869697a39684848c">[email protected]</a>:~$ crontab -l | tail -2
# m h  dom mon dow   command
@reboot /home/avanderneut/bin/on_reboot
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="d2b3a4b3bcb6b7a0bcb7a7a692a7b5b5bd">[email protected]</a>:~$ vi /home/avanderneut/bin/on_reboot
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="ea8b9c8b848e8f98848f9f9eaa9f8d8d85">[email protected]</a>:~$ more !$
more /home/avanderneut/bin/on_reboot
#! /bin/bash
echo "Reboot script" > /var/tmp/xxx
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="3756415659535245595242437742505058">[email protected]</a>:~$ chmod 755 /home/avanderneut/bin/on_reboot
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="ea8b9c8b848e8f98848f9f9eaa9f8d8d85">[email protected]</a>:~$ ls /var/tmp
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="fb9a8d9a959f9e89959e8e8fbb8e9c9c94">[email protected]</a>:~$ /home/avanderneut/bin/on_reboot
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="58392e39363c3d2a363d2d2c182d3f3f37">[email protected]</a>:~$ ls /var/tmp
xxx
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="cdacbbaca3a9a8bfa3a8b8b98db8aaaaa2">[email protected]</a>:~$ rm /var/tmp/xxx
<a href="https://getridbug.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="cfaeb9aea1abaabda1aababb8fbaa8a8a0">[email protected]</a>:~$ sudo reboot
[sudo] password for avanderneut:

And see that after reboot the file /var/tmp/xxx is there although it was not there before rebooting.

This was done with cron version 3.0.

You have to make sure that no services discs etc are used that might not be available at the time the script runs. Start with something simple like the above and make sure it has no terminal output as email is probably not up and running.

You might aslo need a more up-to-date cron (or an upgrade from oracle-linux) if this did not work for you and you need this feature.

Method 6

I would say yes for the question. Just had difficulties with running cron on reboot (Debian 3.10.70) and managed to solve with:

@reboot root /usr/bin/python3 /path/to/script

And a newline character ‘n’ in the end

This is the contents of file:

/etc/cron.d/runOnReboot

Finally, I think it is worth noting an abstract from man 5 crontab

…
The format of a cron command is very much the V7 standard, with a number of upward-compatible extensions. Each line has five time and date
fields, followed by a command, followed by a newline character (‘n’). The system crontab (/etc/crontab) uses the same format, except that the
username for the command is specified after the time and date fields and before the command. The fields may be separated by spaces or tabs. The
maximum permitted length for the command field is 998 characters.
…

Method 7

I use as below

export EDITOR=gedit && sudo crontab -e
@reboot /home/usuario/script.sh

Method 8

First of all, you should login as root:

sudo -i

Then open crontab:

crontab -e

After that, add your script to crontab as root like below:

@reboot root /home/user1/Desktop/my_script

As a result I saw that my script work right.

Note: If you edit crontab with your current user, the reboot cannot call your script properly.

Method 9

prueba:

[email protected]:~$ touch script.sh
[email protected]:~$ chmod +x script.sh

[email protected]:~$ $crontrab -e

@reboot /home/usuario/script.sh

save and restart your pc

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0