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.

There is no portable way to do this. There is a program https://github.com/nelhage/reptyr that can do this on Linux (it uses ptrace and interposes all the system calls), but I don't know how reliable it is or if it is still maintained. YMMV.

You should look for modern alternatives like tmux.

tmux is superior to screen for many reasons, here are just some examples:

• Windows can be moved between session and even linked to multiple sessions
• Windows can be split horizontally and vertically into panes
• Support for UTF-8 and 256 colour terminals
• Sessions can be controlled from the shell without the need to enter a session

Basic Functionality

To get the same functionality as explained in the answer recommending screen, you would need to do the following:

• ssh into the remote machine
• start tmux by typing tmux into the shell
• start the process you want inside the started tmux session
• leave/detach the tmux session by typing Ctrl+b and then d

You can now safely log off from the remote machine, your process will keep running inside tmux. When you come back again and want to check the status of your process you can use tmux attach to attach to your tmux session.

If you want to have multiple sessions running side-by-side, you should name each session using Ctrl+b and $. You can get a list of the currently running sessions using tmux list-sessions or simply tmux ls, now attach to a running session with command tmux attach-session -t <session-name>.

tmux can do much more advanced things than handle a single window in a single session. For more information have a look in man tmux or the tmux GitHub page. In particular, here's an FAQ about the main differences between screen and tmux.

From my testing on tmux 2.6, you'll need two things for the command to move an entire window over:

• The name of the session you want to move the window from (for future reference, $session_name)
• The index of the window you want to move (in the session it's currently in, of course -- we'll call this $window_index). This is actually optional -- if you omit this, then it defaults to the window in focus in the session you're pulling the window from.

From this point, you can just change to the session you want to move the window into, <tmux-escape>: into a command prompt, and type a command of this form:

move-window -s $session_name[:$window_index]

...where, as noted before, the $window_index is optional (as indicated by the square brackets, which aren't actually part of the syntax ). To use some concrete examples:

# Moves from currently-focused window from session named `$session_name`
move-window -s $session_name

# Moves from window with index `$window_index` from 
# session named `$session_name` into the current session
move-window -s $session_name:$window_index

Et voilà! Your window got moved. :)

EDIT: Added some more info on an alternative that omits $window-index.

The latest version of tmux (1.7) supports renumbering of windows.

If you just want to change the number of window 4 to 3, do this in window 4:

move-window -t 3

As Tim said, type fg to bring the last process back to foreground.

If you have more than one process running in the background, do this:

$ jobs
[1]   Stopped                 vim
[2]-  Stopped                 bash
[3]+  Stopped                 vim 23

fg %3 to bring the vim 23 process back to foreground.

To suspend the process running in the background, use:

kill -STOP %job_id

The SIGSTOP signal stops (pauses) a process in essentially the same way Ctrl+Z does.

example: kill -STOP %3.

sources:

• How to send signals to processes in Linux and Unix
• How to manage background and foreground jobs.