How can I reattach to tmux process

I had to reboot my box today. I had several program running in tmux sessions. They seem to be still alive, how can I reattach to them? I tried tmux a processID but it didn't work.

/home/me 21$ ps aux | grep tmux
me    1299  0.0  0.0  22244  1920 ?        Ss   Apr28   0:40 tmux -2 -f /tmp/r-plugin-me/tmux.conf new-session -s vimrpluginme1398670569alnn51oynp1vollnn51f2v4r_ied_delta1meRalphaCalibr VIMINSTANCEID=alnn51oynp1vollnn51f2v4r_ied_delta1meRal
me    2575  0.0  0.0  54164  3500 ?        S    07:35   0:00 xterm -e tmux -2 -f /home/me/.tmux.conf -S /tmp/vX0qRrR/78
me    2577  0.0  0.0  19892  1400 pts/2    Ss+  07:35   0:00 tmux -2 -f /home/me/.tmux.conf -S /tmp/vX0qRrR/78
me    2579  0.0  0.0  22128  1832 ?        Ss   07:35   0:00 tmux -2 -f /home/me/.tmux.conf -S /tmp/vX0qRrR/78
me    5155  0.0  0.0   6380   756 pts/4    S+   07:46   0:00 grep tmux
me   31340  0.0  0.0  23348  3000 ?        Ss   Apr28   0:17 tmux -2 -f /home/me/.tmux.conf -S /tmp/vIqEM06/78

You can not re-attach a process id. You need to reattach the corresponding tmux session.

So do tmux ls. Pick whatever session you want to re-attach. Then do tmux attach -d -t <session id> to re-attach it to a new tmux instance and release it from the old one.

If you only have one session detached you can just do

tmux attach

also if you're going to be working in multiple sessions it might be a good idea to name your sessions

tmux new -s ssh-to-staging
Ctrl b, d   # Detach from session
tmux new -s ssh-to-s3
Ctrl b, d   Detach from session

now when you do tmux ls you can reattach more easily without guessing.

tmux attach -d -t ssh-to-s3

You also might wanna bookmark this cheat sheet