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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?

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6 Answers 6

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.

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2  
for file in /etc/local/runonce.d/*, no? –  pra Jun 5 '10 at 5:00
    
@pra: Thanks for spotting that. –  Dennis Williamson Jun 5 '10 at 5:25
    
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! –  Christopher Parker Jun 9 '10 at 18:51
    
What made you choose local3, versus any of the other facilities between 0 and 7? –  Christopher Parker Jun 10 '10 at 19:49
2  
@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. –  Dennis Williamson Jun 10 '10 at 20:19

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.

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in redhat and debian systems you can do that from /etc/rc.local, it's a kind of autoexec.bat.

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4  
That's going to get executed at each boot not just the next one only. –  Dennis Williamson Jun 5 '10 at 22:46
1  
my bad, I misread the question. Thanks for the correction –  natxo asenjo Jun 6 '10 at 8:30
up vote 11 down vote accepted

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.

myuser@myhost:/home/myuser$ sudo runonce foo
myuser@myhost:/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 $)
@reboot /root/.runonce_foo
myuser@myhost:/home/myuser$ 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.
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Your script looks really handy. One thing to note is that it destructively strips comments out of the crontab. –  Dennis Williamson Jun 9 '10 at 21:39
    
@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 Jun 9 '10 at 21:47
    
@Dennis: Done. The patterns could probably be better, but it works for me. –  Christopher Parker Jun 9 '10 at 22:02
    
@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.) –  Christopher Parker Jun 10 '10 at 23:24

Set up the script in /etc/rc5.d with an S99 and have it delete itself after running.

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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

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