SSH with Pseudo-terminal

It’s pretty common for me to execute the same commands on a remote machine everyday. I usually do something like:

$ ssh <>
$ screen -x   # reattach to irssi screen session

The most obvious optimization to make is to edit the ~/.ssh/config file to alias to something easier to type, like just machine. Now I can just type:

$ ssh machine
$ screen -x

Of course, it would be nice if I didn’t have to type screen -x each time as well. We can solve this by passing the commands to run on the remote maching as arguments to the ssh command. So we try:

$ ssh machine 'screen -x '
Must be connected to a terminal.

Uh oh. The remote machine is unable to start screen because, by default, a tty (a pseudoterminal), isn’t created when we execute remote commands. To work around this we need to pass the magic -t option. This forces the remote machine to create a tty for us.

$ ssh machine -t 'screen -x '

Voila! Worked like a charm. And this is useful for a bunch of typical commands you’d like to run on a remote server, for example:

$ ssh machine -t 'top'  # grab stats

$ ssh machine -t 'watch ps -eaf | grep <blah>'

The final optimization we can make is to alias the whole command to something easier to type. Since I like to keep my aliases in a separate ~/.bash_aliases file, I’d run:

$ echo alias irc='ssh machine -t "screen -x"' >> ~/.bash_aliases

Now, all I have to do is type irc each morning and I’m right back into my IRC session.

Posted on 03 June 2011.
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