The first hit on google provides all information needed:
Add this line to
/etc/rc.local (using administrator privileges):
sudo -H -u USER screen -d -m -S irssi-proxy irssi
Replace USER with your username. Explanation of the command:
sudo ; runs command as user
-H ; sets the home directory to the users
-u ; sets the command to act as USER
screen ; the command sudo is executing
-d -m ; starts screen detached. This solves a lot of issues later.
-S ; starts the screen session with the irssi-proxy ID.
irssi ; the command we're launching
You will have to install
screen to make this work (screen is a very nice little tool to run command line applications in the background).
If you want to get your irssi in the foreground later you can do that by running
screen -r irssi-proxy in a terminal.
Alternatively you can use crontab to have it run as boot (saves you from changing system files in /etc):
crontab -e as your User. Add this line:
@reboot screen -d -m -S irssi-proxy irssi
It will basically have the same affect as the entry in rc.local.