tmux not re-attaching

Question

I recently switched from using screen to tmux (obtained through macports), as I like the feature set more. However, I can't seem to get tmux to reattach from an alternate location, like I can screen.

At home on my mac, I will open up iTerm2, my default shell is zsh, and I will begin a tmux session with tmux. I get all my spits set up, ssh'd into the proper servers, etc., and work for a while. Time to go to work. <C-a> d - tmux detaches.

I get to work, where I use a windows xp machine. I fire up putty, ssh into my mac back at home, attempt a tmux attach, and get an error message:

no sessions

I cannot seem to determine why this would happen. I am not afraid to dig into this, but don't even know where to start. Thoughts?

P.S. I have already removed my .tmux.conf file, so it's using the default config.

Answer 1

In my case, apparently temp folder was cleaned.
This blog post helped me recover my “lost” session:

I finally got the solution: sending the signal 10 forced tmux to recreate sockets. After that I could run tmux again without losing my session:

$ killall -10 tmux

Answer 2

tmux stores its server socket in a directory under the directory specified by the TMPDIR environment variable.

In your GUI session you probably end up with a TMPDIR that points to somewhere under /var (e.g. /var/folders/mV/mVip4IQ4EXOriTiLJmeSuk+++Tc/-Tmp-/).

When you are logged in through SSH, you probably end up without a TMPDIR set, so tmux looks under /tmp/ for its socket.

On a 10.6 system, here is my TMPDIR with zsh/Terminal, and with zsh/SSH:

% echo local: ${TMPDIR-unset}; ssh localhost 'echo remote: ${TMPDIR-unset}'
local: /var/folders/mV/mVip4IQ4EXOriTiLJmeSuk+++Tc/-Tmp-/
remote: unset

If you know the value you need to use for TMPDIR, you can specify it when attaching (or running some other tmux command outside of the session itself):

TMPDIR=/var/folders/mV/mVip4IQ4EXOriTiLJmeSuk+++Tc/-Tmp-/ tmux attach

If you do not know the directory your GUI session was using you might be able to find it with something like this (the syntax is specific to zsh; it searches under /var/folders/ for a directory named -Tmp- that is owned by the current user):

echo /var/folders/**/*/-Tmp-(U/)

To avoid problems in the future, you might want to unset TMPDIR before starting your server (or set it to something that you can more easily predict).