How to run a script during boot as root

Question

I had a script that automatically enables my wifi without using networkmanager, but I don't know how to run the script as root while the system is booting. How do I make the script run automatically during boot?

Answer 1

Place the script you want to run in the /etc/init.d directory and make the script executable.

chmod 755 myscript

Once that is done create a symbolic link in the run level directory you would like to use, for example if you wanted to run a program in the graphical runlevel 2, the default runlevel for Ubuntu, you would place it in the /etc/rc2.d directory. You just cannot place it the directory, you must signify when it will run by indicating the startup with an “S” and the execution order is important. Place it after everything else that is in the directory by giving it a higher number.

If the last script to be run is rc.local and it is named S99rc.local then you need to add your script as S99myscript.

ln -s /etc/init.d/myscript /etc/rc3.d/S99myscript

Each backward compatible /etc/rc*.d directory has symbolic links to the /etc/init.d/ directory.

Answer 2

Use a crontab option to make your script run after reboot,

You can do this by adding your command prefixed with the @reboot nonstandard predefined scheduling definition in cron.

Open crontab as the root user (you must use sudo here in order to edit your root's crontab instead of your user's crontab):

sudo crontab -e

Then, add a record to the bottom, containing your desired command to be run as root:

@reboot path/to/your/executable/to/be/run/as/root 

That will do what you want.

Note that you can see your user's and root's crontab entries as follows:

crontab -l       # list your user crontab entries
sudo crontab -l  # list root's crontab entries

For your command to run as root, it must be in your root's crontab.

Answer 3

Include the command in /etc/rc.local. It will be run whenever the user's runlevel changes.

Note: You have to put the command before the last line in /etc/rc.local that contains: "exit 0".

Answer 4

This worked for me on Ubuntu 17.04:

1. create a script file like disable_cdrom in convenient for you location. In my case home/yterle/disable_cdrom. In my case:

   #!/bin/sh
   eject /dev/sr0 -i 1
   

2. make it executable chmod 775 disable_cdrom

3. navigate to /etc/systemd/system and create there a service file. For example sudo gedit /etc/systemd/system/disable_cdrom.service

My disable_cdrom.service looks like this:

[Unit]
Description=Disable cdrom

[Service]
Type=oneshot
ExecStart=/bin/sh /home/yterle/disable_cdrom

[Install]
WantedBy=multi-user.target

Where ExecStart points to run your script with /bin/sh

Then run systemctl enable disable_cdrom.service to enable the systemd service

Answer 5

Include your Script file to /etc/init.d/ with Executable permission then set different run level

$ update-rc.d script-name default

It will put your script on boot startup.

Answer 6

Create a text file like this in /etc/cron.d/:

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

@reboot   root    yourScriptPath

(You should replace yourScriptPath with the path to the script you want to run.)

Answer 7

Careful with adding the script to rc.local - I was stuck in splash screen because of it. Pressing Alt+F1 revealed what was going on behind the splash screen (the script in rc.local was running).

I could not get out of it.

• Ctrl+Alt+Del or
• Alt+PrtSc+K or
• Ctrl+Alt+F#

nothing works.

I had to boot from a USB Ubuntu image, find rc.local, give myself permissions to file and delete it. I guess you shouldn't do stuff if you don't know what you're doing.

Answer 8

You can create a service under systemd. That way your script will run as sudo automatically.

Assuming you have a script /path/to/script/my_amazing_script.sh that you want to run at ever boot as root:

Make sure only root can work with this:

chmod 0700 /path/to/script/my_amazing_script.sh

Then create the service file and start editing it:

sudo nano /etc/systemd/system/run_amazing_script.service

Put this in the file:

[Unit]
Description=Run the best script ever

[Service]
ExecStart=/path/to/script/my_amazing_script.sh

[Install]
WantedBy=multi-user.target

Check the service runs fine by running it one time:

sudo systemctl start run_amazing_script.service

Check the log:

sudo journalctl -u run_amazing_script.service

If you are happy with the run, enable it to make it run upon every boot:

sudo systemctl enable run_amazing_script.service

And if you want to stop it from running at every boot you can disable it:

sudo systemctl disable run_amazing_script.service

Note: this solution is very similar to what YTerle posted. But since I don't have enough rep I couldn't comment nor upvote his answer