How to attach to an existing tmux session?

To get the list of existing tmux session use tmux ls command.

> tmux ls
0: 1 windows (created Wed Dec 16 16:45:19 2020)

Here there is one session that already exists. To attach to this particular session ‘0’ we can use the following command.

> tmux attach-session -t 0

This will open the existing tmux session.