Linux: Schedule command to run once after reboot (RunOnce equivalent)

Question

I'd like to schedule a command to run after reboot on a Linux box. I know how to do this so the command consistently runs after every reboot with a @reboot crontab entry, however I only want the command to run once. After it runs, it should be removed from the queue of commands to run. I'm essentially looking for a Linux equivalent to RunOnce in the Windows world.

In case it matters:

$ uname -a
Linux devbox 2.6.27.19-5-default #1 SMP 2009-02-28 04:40:21 +0100 x86_64 x86_64 x86_64 GNU/Linux
$ bash --version
GNU bash, version 3.2.48(1)-release (x86_64-suse-linux-gnu)
Copyright (C) 2007 Free Software Foundation, Inc.
$ cat /etc/SuSE-release
SUSE Linux Enterprise Server 11 (x86_64)
VERSION = 11
PATCHLEVEL = 0

Is there an easy, scriptable way to do this?

Solution 1

I really appreciate the effort put into Dennis Williamson's answer. I wanted to accept it as the answer to this question, as it is elegant and simple, however:

• I ultimately felt that it required too many steps to set up.
• It requires root access.

I think his solution would be great as an out-of-the-box feature of a Linux distribution.

That being said, I wrote my own script to accomplish more or less the same thing as Dennis's solution. It doesn't require any extra setup steps and it doesn't require root access.

#!/bin/bash
if [[ $# -eq 0 ]]; then
    echo "Schedules a command to be run after the next reboot."
    echo "Usage: $(basename $0) <command>"
    echo "       $(basename $0) -p <path> <command>"
    echo "       $(basename $0) -r <command>"
else
    REMOVE=0
    COMMAND=${!#}
    SCRIPTPATH=$PATH
    while getopts ":r:p:" optionName; do
        case "$optionName" in
            r) REMOVE=1; COMMAND=$OPTARG;;
            p) SCRIPTPATH=$OPTARG;;
        esac
    done
    SCRIPT="${HOME}/.$(basename $0)_$(echo $COMMAND | sed 's/[^a-zA-Z0-9_]/_/g')"
    if [[ ! -f $SCRIPT ]]; then
        echo "PATH=$SCRIPTPATH" >> $SCRIPT
        echo "cd $(pwd)"        >> $SCRIPT
        echo "logger -t $(basename $0) -p local3.info \"COMMAND=$COMMAND ; USER=\$(whoami) ($(logname)) ; PWD=$(pwd) ; PATH=\$PATH\"" >> $SCRIPT
        echo "$COMMAND | logger -t $(basename $0) -p local3.info" >> $SCRIPT
        echo "$0 -r \"$(echo $COMMAND | sed 's/\"/\\\"/g')\""     >> $SCRIPT
        chmod +x $SCRIPT
    fi
    CRONTAB="${HOME}/.$(basename $0)_temp_crontab_$RANDOM"
    ENTRY="@reboot $SCRIPT"
    echo "$(crontab -l 2>/dev/null)" | grep -v "$ENTRY" | grep -v "^# DO NOT EDIT THIS FILE - edit the master and reinstall.$" | grep -v "^# ([^ ]* installed on [^)]*)$" | grep -v "^# (Cron version [^$]*\$[^$]*\$)$" > $CRONTAB
    if [[ $REMOVE -eq 0 ]]; then
        echo "$ENTRY" >> $CRONTAB
    fi
    crontab $CRONTAB
    rm $CRONTAB
    if [[ $REMOVE -ne 0 ]]; then
        rm $SCRIPT
    fi
fi

Save this script (e.g.: runonce), chmod +x, and run:

$ runonce foo
$ runonce "echo \"I'm up. I swear I'll never email you again.\" | mail -s \"Server's Up\" $(whoami)"

In the event of a typo, you can remove a command from the runonce queue with the -r flag:

$ runonce fop
$ runonce -r fop
$ runonce foo

Using sudo works the way you'd expect it to work. Useful for starting a server just once after the next reboot.

[email protected]:/home/myuser$ sudo runonce foo
[email protected]:/home/myuser$ sudo crontab -l
# DO NOT EDIT THIS FILE - edit the master and reinstall.
# (/root/.runonce_temp_crontab_10478 installed on Wed Jun  9 16:56:00 2010)
# (Cron version V5.0 -- $Id: crontab.c,v 1.12 2004/01/23 18:56:42 vixie Exp $)
@reboot /root/.runonce_foo
[email protected]:/home/myuser$ sudo cat /root/.runonce_foo
PATH=/usr/sbin:/bin:/usr/bin:/sbin
cd /home/myuser
foo
/home/myuser/bin/runonce -r "foo"

Some notes:

• This script replicates the environment (PATH, working directory, user) it was invoked in.
• It's designed to basically defer execution of a command as it would be executed "right here, right now" until after the next boot sequence.

Solution 2

Create an @reboot entry in your crontab to run a script called /usr/local/bin/runonce.

Create a directory structure called /etc/local/runonce.d/ran using mkdir -p.

Create the script /usr/local/bin/runonce as follows:

#!/bin/sh
for file in /etc/local/runonce.d/*
do
    if [ ! -f "$file" ]
    then
        continue
    fi
    "$file"
    mv "$file" "/etc/local/runonce.d/ran/$file.$(date +%Y%m%dT%H%M%S)"
    logger -t runonce -p local3.info "$file"
done

Now place any script you want run at the next reboot (once only) in the directory /etc/local/runonce.d and chown and chmod +x it appropriately. Once it's been run, you'll find it moved to the ran subdirectory and the date and time appended to its name. There will also be an entry in your syslog.

Solution 3

Create e.g. /root/runonce.sh:

#!/bin/bash
#your command here
sed -i '/runonce.sh/d' /etc/rc.local

Add to /etc/rc.local:

/root/runonce.sh

Solution 4

I think this answer is the most elegant:

Place script in /etc/init.d/script and self-delete with last line: rm $0

Unless the script is 100% fail-proof, probably wise to handle exceptions to avoid a fatal error loop..

Solution 5

I used chkconfig to have my system automatically run a script once after boot and never again. If your system uses ckconfig (Fedora, RedHat, CentOs, etc) this will work.

First the script:

#!/bin/bash
# chkconfig: 345 99 10
# description: This script is designed to run once and then never again.
#
##
# Beginning of your custom one-time commands
#
plymouth-set-default-theme charge -R
dracut -f
#
# End of your custom one-time commands
##
##
# This script will run once
# If you would like to run it again.  run 'chkconfig run-once on' then reboot.
#
chkconfig run-once off
chkconfig --del run-once

1. Name the script run-once
2. Place the script in /etc/init.d/
3. Enable the script chkconfig run-once on
4. reboot

When the system boots your script will run once and never again.

That is, never again unless you want it to. You can always re-enable the script with the chkconfig run-once on command.

I like this solution because it puts one and only one file on the system and because the run-once command can be re-issued if needed.

View more solutions

Comments

[BillThor]

RunOnce is an artifact of Windows resulting from problems completing configuration before a reboot. Is there any reason you can't run your script before reboot? The above solution appears to be a reasonable clone of RunOnce.

[Admin]

I'm surprised there isn't a nice tool for this. Or maybe there is and I haven't discovered it yet.

[Dennis Williamson]

That's going to get executed at each boot not just the next one only.

[Christopher Parker]

Thanks for your answer. This solution is great. It technically solves my problem, however it seems like there's a lot of preparation of infrastructure required to make this work. It's not portable. I think your solution would ideally be baked into a Linux distribution (I'm not sure why it isn't!). Your answer inspired my ultimate solution, which I've also posted as an answer. Thanks again!

[Dennis Williamson]

Your script looks really handy. One thing to note is that it destructively strips comments out of the crontab.

[Christopher Parker]

@Dennis: Thanks. I originally didn't have that extra grep call in there, but all of the comments were piling up; three for every time I ran the script. I think I'll change the script to just always remove comment lines that look like those three auto-generated comments.

[Christopher Parker]

@Dennis: Done. The patterns could probably be better, but it works for me.

[Christopher Parker]

What made you choose local3, versus any of the other facilities between 0 and 7?

[Dennis Williamson]

@Christopher: A dice roll is always the best method. Seriously, though, for an example it didn't matter and that's the key my finger landed on. Besides, I don't own any eight-sided die.

[Christopher Parker]

@Dennis: Got it, thanks. Coincidentally, local3 is the local facility that appears in man logger.

[Christopher Parker]

@Dennis: Actually, based on crontab.c, I think my patterns are just fine. (Search for "DO NOT EDIT THIS FILE" at opensource.apple.com/source/cron/cron-35/crontab/crontab.c.)

[Andrew Savinykh]

Does the $file variable contain full path or just the file name?

[Dennis Williamson]

@AndrewSavinykh: The full path.

[Andrew Savinykh]

@DennisWilliamson, thank you, I got this working with systemd instead of cron. Your help is much appreciated ;)

[CarComp]

This is pure genius. Don't forget to chmod +x the /root/runonce.sh. This is perfect for apt-get upgrade on azure machines that hang because walinuxagent blocks the dpkg

[mleu]

Beware that if your system takes longer than 2 minutes until atd is stopped your command may run during shutdown. This could be avoided by stopping atd before sheduling the command with atd now and then rebooting.

[iBug]

This is too hacky (though it's also what I came up with at first).