automatically start tmux when ssh into a box #zsh #shell

.zshrc

# inside your .bashrc or .zshrc (on the server side) add:

# start tmux if we ssh into the box
if [[ -n "$PS1" ]] && [[ -z "$TMUX" ]] && [[ -n "$SSH_CONNECTION" ]]; then
    tmux attach-session -t $USER || tmux new-session -s $USER
fi

# this will attach to an ongoing tmux session or start a new one
# the session name will be the name of the user ($USER)

Cool, thank you @leenzhu