I am not very familiar with tmux but it runs for everyday work.

Sometimes, I input Ctrlbd, then the tmux window disappears and the screen shows

xxx@bsa0248:~$ tt
[detached (from session 3)]

Then if I input the following command, I get some strange output:

xxx@bsa0248:~$ tmux ls
0: 3 windows (created Sun Jun 10 16:39:33 2018) [123x32]
1: 3 windows (created Sun Jun 10 16:43:10 2018) [123x32]
2: 3 windows (created Sun Jun 10 17:14:23 2018) [98x29]

Does anyone know what this means?

Related OS is Ubuntu

xxx@bsa0248:~$ cat /etc/issue
Ubuntu 9.10 \n \l

1 Answer 1


tmux ls, which is an alias for tmux list-sessions, lists all the active sessions managed by the tmux server you’re connected to.

The output you’re getting means there are three sessions running, each with three windows. The numbers between square brackets show the terminal size of each session.

When working on multiple tmux sessions, it's useful to initialized them with a name, using

tmux new -s SessionName

so that in the list you'll see the SessionName instead of a number in the first column of the output of tmux ls. Of course you can also rename an already-open session, see this question.

  • Hi Kitt, Thank you for your reply. I see now. But recently I find tmux ls can't work and error output is below: Do you know why? Thanks @bsa0483:~$ tt [detached (from session 0)] Tom@bsa0483:~$ tmux ls server not found: No such file or directory Tom@bsa0483:~$ Tom@bsa0483:~$ tmux list-sessions server not found: No such file or directory Tom@bsa0483:~$ Jun 30, 2018 at 10:17
  • That means it can’t find your server, but I don’t know why. Jun 30, 2018 at 13:30

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