Scribbles for my memory

Both prevent a process from dying when you close the terminal, but they work at different stages and with different guarantees.

nohup intervenes before launch. It sets the process itself to ignore SIGHUP via sigaction, so no matter who sends the signal, the process won't react. It also redirects stdout/stderr to nohup.out (or a file you specify). POSIX-standard, portable to any shell.

disown intervenes after launch. It removes the process from the shell's job table so the shell won't notify it on exit — but the process has no built-in signal immunity. Some SSH/terminal implementations broadcast SIGHUP to the entire process group on disconnect, bypassing the shell entirely. In that case disown alone won't save you.

# nohup: know you need it upfront
nohup python train.py > train.log 2>&1 &

# disown: the "oh crap I need to leave" rescue
./long_task.sh        # already running...
# Ctrl+Z to suspend, then:
bg
disown %1

# Belt and suspenders — use both
nohup cmd > out.log 2>&1 &
disown

The combination is the safest one-liner: nohup gives the process its own signal shield, disown cleans up the job table so closing the terminal is truly a no-op.

For anything long-lived (a server, a daemon), neither is the right tool — use systemd, supervisord, or tmux. nohup and disown are emergency measures, not service managers.

One gotcha with nohup: if you don't redirect output yourself, it writes to ./nohup.out, which can quietly grow to fill a disk. Always pair it with an explicit > log 2>&1.