To run a lightweight process in the background on the login node, you can use tmux to preserve the process even when the SSH session is terminated.
Running tmux new -s launcher will create a new tmux session named launcher. To exit the tmux session while still preserving any running jobs on the login node, press ctrl+b followed by d. To re-enter the tmux session, run tmux attach -t launcher.
Additional tmux commands can be found on the tmux cheatsheet and in the Princeton Research Computing guide .