Ssh – How to launch a screen session with a command over ssh on a remote server from the desktop

gnu-screensshterminaltty

I want to be able to launch screen sessions on remote servers from a single ssh command on my desktop. However, screen seems to need a terminal, which is not available when running a command through ssh.

So the obvious

ssh root@my.machine screen "tail -f /var/log/messages"

(as an example) does not work, and gives

Must be connected to a terminal.

I want ssh to launch the command under a screen so I can log in later and attach as I would to a screen session I would have launched manually.

Best Answer

Try using the -t option to ssh

ssh -t root@my.machine screen "tail -f /var/log/messages"

From man ssh

-t      Force pseudo-tty allocation.  This can be used to execute arbi-
        trary screen-based programs on a remote machine, which can be
        very useful, e.g., when implementing menu services.  Multiple -t
        options force tty allocation, even if ssh has no local tty.

Related Solutions

Linux – Moving an already-running process to Screen

Have a look at reptyr, which does exactly that. The github page has all the information.

reptyr - A tool for "re-ptying" programs.

reptyr is a utility for taking an existing running program and attaching it to a new terminal. Started a long-running process over ssh, but have to leave and don't want to interrupt it? Just start a screen, use reptyr to grab it, and then kill the ssh session and head on home.

USAGE

reptyr PID

"reptyr PID" will grab the process with id PID and attach it to your current terminal.

After attaching, the process will take input from and write output to the new terminal, including ^C and ^Z. (Unfortunately, if you background it, you will still have to run "bg" or "fg" in the old terminal. This is likely impossible to fix in a reasonable way without patching your shell.)

Run (GNU) Screen from script

The screen -S test -X screen command command is what you need to add windows to your daemon session, but not for the reasons you give. It works because -X takes a screen command and not a shell command, and the screen command to create a window is called, confusingly, screen. There is no exec screen command. There is no chaining either, unless you build your command using shell scripting (like this: screen -S script -X screen sh -c 'command1; command2;').

Calling screen -S test -X screen with no command is useless because the default command is a shell, and once you have spawned a shell, you don't have a noninteractive (and non-devious) way to run commands inside that shell. It is better to run the command by itself, without an interactive shell. A side effect is that when the command exits, the screen window doesn't have a child any more, and will close.

Now, you can ask screen to hold the window open anyway, after the command has quit. Use the zombie screen command to enable that. Your sequence looks like:

screen -d -m -S script
screen -S script -X zombie qr
screen -S script -X screen tail -f /var/log/messages
screen -S script -X screen tail -f /var/log/xinetd.log

To reattach interactively:

screen -S script -r

And finally, you can rewrite these -X commands as a screenrc script instead.

Screenrc:

zombie qr
screen tail -f /var/log/messages
screen tail -f /var/log/xinetd.log

Script:

screen -d -m -S script -c screenrc

Best Answer

Related Solutions

Linux – Moving an already-running process to Screen

reptyr - A tool for "re-ptying" programs.

USAGE

Run (GNU) Screen from script

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