Linux screen command: sessions, detach, reattach, scroll and logs

Install screen and start a named session

On Debian and Ubuntu, install GNU screen with sudo apt install screen; on Fedora, use sudo dnf install screen. Run screen -v to check the version. These examples were tested on screen 5.0.2 from July 2026 and on the 4.09.01 build in Debian 13, which behave the same for everything here.

sudo apt install screen
screen -v
screen -S train

Give every session a name so you can find it later: screen -S train opens one called train. Everything inside screen starts with Ctrl-a: press Ctrl-a, let go, then press the next key. Ctrl-a ? shows the full list.

Detach and reattach

Press Ctrl-a d to detach and leave everything running. Ctrl-a D D detaches and logs you out of the SSH session in one go.

Run screen -ls from your normal shell to see what is running. With nothing running it prints No Sockets found in ... and exits with status 1.

$ screen -ls
There is a screen on:
        7583.train      (10/30/26 00:12:21)     (Detached)
1 Socket in /run/screen/S-user.

To get back in, run screen -r train, or just screen -r when there is only one session. If the list shows (Attached) because an old SSH connection did not close cleanly, screen -d -r train detaches that terminal and attaches here; screen -D -r train logs the other side out too. screen -x train attaches without detaching anyone, so two terminals share one view.

Windows and split regions

One session can hold several shell windows. Ctrl-a c creates one, Ctrl-a n and Ctrl-a p step through them, Ctrl-a 0 to Ctrl-a 9 jump to a number and Ctrl-a Ctrl-a flips back to the last one.

With several open, Ctrl-a A names the current window so Ctrl-a " shows a readable list. Ctrl-a k kills a window after asking first, and Ctrl-a \ asks once and then kills all windows and the session.

Ctrl-a S splits the display top and bottom and Ctrl-a | splits it left and right. A new region starts out blank: press Ctrl-a Tab to move into it and Ctrl-a c to start a shell. Ctrl-a X removes the current region and Ctrl-a Q keeps only the one you are in.

Scrollback, copy mode and logs

screen keeps its own history for each window, so your terminal's scrollbar and mouse wheel usually do not show it. Press Ctrl-a [ (or Ctrl-a Esc) to enter copy mode. Move with the arrow keys or h, j, k, l, scroll half a page with Ctrl-u and Ctrl-d and a full page with Ctrl-b and Ctrl-f, and jump to the top or bottom with g and G.

Press Space or Enter once to set the first mark and again to set the second; that copies the text between them and leaves copy mode. Ctrl-a ] pastes it. Keys without a copy mode meaning, such as Esc or q, leave without copying.

The compiled default for defscrollback is only 100 lines, and Debian's /etc/screenrc raises it to 1,024. Start with screen -h 10000 or put defscrollback 10000 in ~/.screenrc so long output does not roll off the top.

echo 'defscrollback 10000' >> ~/.screenrc
screen -L -Logfile train.log -S train

-L writes everything the window prints to a log file. Without -Logfile, screen writes screenlog.0 in the directory where you started it, where 0 is the window number. Ctrl-a H toggles logging for the current window, and screen flushes the log to disk every 10 seconds by default (logfile flush).

If logging was off, screen -S train -X hardcopy -h /tmp/train.txt dumps the window and its scrollback to a file.

Run a job in a detached screen

screen -dmS train python -u train.py starts a detached session running the command, but the window closes and the session ends as soon as the command exits. To keep the shell and the final output, start an empty session, type the command into it with stuff and quit it from outside when you are done:

screen -dmS train
screen -S train -X stuff 'python -u train.py\n'
screen -r train
screen -S train -X quit

screen expands $NAME variables inside the stuff string before the shell sees it, so write a literal dollar sign as \$. Other ways to keep a job alive without a multiplexer are in the nohup guide.

Checking on the job still means SSHing back in and reattaching just to see whether it finished.