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?

Answer 1

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.

Answer 2

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.

Answer 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

Answer 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..

Answer 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.

Answer 6

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

Answer 7

You can do this with the at command, although I notice you can't (at least on RHEL 5, which I tested on) use at @reboot or at reboot, but you can use at now + 2 minutes and then shutdown -r now.

This doesn't require that you system take longer than 2 minutes to run.

It may be useful where you want 0 set-up, although I do rather wish the 'runonce' command was standard kit.

Answer 8

To flesh out the suggestion from @mleu, for CentOS 7 you can do the following:

1. Stop 'atd':

• systemctl stop atd.service

2. Register action with 'atd':

• echo "bash '/var/tmp/myOnBootScript.sh'" | at now

3. Reboot:

• systemctl reboot

This will run the script on boot, as soon as the 'atd' service is up and running. If you need to delay the script while other things finish starting up, like a web server or something, you can include that in your script. For example:

1. systemd status:

• systemctl status mywebserver.service

2. In-built status tools:

• pg_isready -U "${db_Super_User}" -d "${database_Name}"

3. Direct verification the service is responding as expected:

• psql -U "${db_Super_User}" -d "${database_Name}" -c "\\d pg_class"

Answer 9

Adapting solutions from @kaffeslangen, @geotheory and @CameronKerr, below is one that I used at the end of a VM bootstrapping script. The build script is executed via cloud-init on a new EC2 instance from an Ubuntu AMI. It installs and configures a bunch of stuff on first boot, and then reboots the system ready for use.

I wanted to send an email after the reboot with the status of the server and the log output from the build process, but only after the system has fully completed booting (otherwise the systemctl status command's output indicates a 'Starting' status and we don't yet know whether the system fully booted without other service failures). Hence the use of the 'at' command below.

Also, since my VM otherwise does not use /etc/rc.local, I can simply write it and then self-delete it, rather than creating a separate script and adding/removing an invocation for that within /etc/rc.local, as was done by @kaffeslangen.

cat <<EOT > /etc/rc.local
#!/bin/bash
systemctl status --all 2>&1 | mail -s 'VM Build Result' [email protected] --attach=/var/log/cloud-init-output.log
rm \$0
EOT

chmod +x /etc/rc.local

reboot

Answer 10

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