tmux and screen: Persistent Terminal Sessions

Long-running processes started over SSH are killed when the connection drops because they are attached to the terminal's process group.

Use tmux (or screen) to run sessions that persist independently of SSH connections.

# tmux — start, detach, reattach
tmux new -s mysession           # Create named session
tmux ls                         # List sessions
tmux attach -t mysession        # Attach to session
tmux kill-session -t mysession  # Kill session

# Inside tmux — key bindings (prefix is Ctrl+B by default)
# Ctrl+B d     = detach
# Ctrl+B c     = new window
# Ctrl+B n/p   = next/previous window
# Ctrl+B %     = split vertically
# Ctrl+B "     = split horizontally
# Ctrl+B [     = scroll mode (q to exit)

# screen — alternative
screen -S mysession             # Create named session
screen -ls                      # List sessions
screen -r mysession             # Reattach
# Ctrl+A d = detach from screen

# Useful: send a command to a tmux session without attaching
tmux send-keys -t mysession 'ls -la' Enter

# Run command in a new detached session
tmux new-session -d -s build -c /app 'make build'

When an SSH connection drops, SIGHUP is sent to the shell and all its child processes. tmux and screen are independent daemon processes — their child processes are not affected by SSH disconnection.