How can I make /etc/rc.local run on startup?

Can you run your script manually; if not, it's a problem with that script, otherwise look more at rc.local. If that script needs to run as root, sudo must be used to manually run it.

• Ensure /etc/rc.local, and the script it call, is executable:

  ls -l /etc/rc.local
    -rwxr-xr-x 1 root root 419 2010-08-27 11:26 /etc/rc.local
  

• Ensure rc.local has a shebang line, which is the default:

  head -n1 /etc/rc.local
    #!/bin/sh -e
  

In my case, none of the instructions were a perfect solution, so try this detailed one:

1. Save all executing code in a separate text file with an arbitrary name, such as foo.sh
2. Add #!/bin/sh as the first line in foo.sh, executing it via sudo foo.sh to check for errors
3. In /etc/rc.local, place the full pathname to foo.sh, prefaced with sh, before exit 0:

   sh '/path/to/your/script/foo.sh'
   

4. Verify the first line in /etc/rc.local is #!/bin/sh -e
5. Ensure /etc/rc.local is executable:

   sudo chown root /etc/rc.local
   sudo chmod 755 /etc/rc.local
   

6. Verify everything works fine:

   sudo /etc/init.d/rc.local start
   

7. Reboot to test

On newer Ubuntu versions systemd is used and /etc/rc.local is not loaded always by default.

Check if the Compatibility service is loaded with

systemctl status rc-local.service

If it contains active (exited) your setting seems fine and you could have another error in your /etc/rc.local file (this could be a command that fails for example).