Re: screen -X

[Bernard Pratz]

On Wed, 2008-12-03 at 15:32 -0800, Jim Lloyd wrote:
> I'd like to so something that I bet savvy unix admins do all the time
> with screen, but I haven't figured out the trick.
> 
> I have a shell script that lets me do this:
> 
> $ each <command>
> 
> The script expands this running the same command on several machines:
> 
> $ ssh host1 <command>
> $ ssh host2 <command>
> ...
> $ ssh hostN <command>
> 
> The script basically works fine, but it executes the commands
> serially. For long running commands, I'd like to run them in parallel.
> Ideally I'd run them in a detached screen session on each machine. The
> ssh command should execute just long enough to start the long running
> command in a detached screen session.

well, like perl people like to say : timtoady, if you don't like the
solutions given in the thread,

the simplest way with screen would be :

-------------------------8<--------------------------8<----------------
ssh host1 "screen -dmS <sessionname>;screen -x <sessionname> -X screen
<command>"
ssh host2 "screen -dmS <sessionname>;screen -x <sessionname> -X screen
<command>"
...
ssh hostN "screen -dmS <sessionname>;screen -x <sessionname> -X screen
<command>"
------------------------->8-------------------------->8----------------

you could also have all run in a local screen, so you see the outputs,
but the commands don't get killed if your connection fails :

-------------------------8<--------------------------8<----------------
screen -dmS <localsessionname>
screen -x <localsessionname> -X screen 'ssh host1 "screen -dmS
<sessionname>;screen -x <sessionname> -X screen <command>"'
screen -x <localsessionname> -X screen 'ssh host2 "screen -dmS
<sessionname>;screen -x <sessionname> -X screen <command>"'
...
screen -x <localsessionname> -X screen 'ssh hostN "screen -dmS
<sessionname>;screen -x <sessionname> -X screen <command>"'
------------------------->8-------------------------->8----------------

and you can manually enter all passwords, or use password-less keys to
send all those commands without entering your password or use stuff :

-------------------------8<--------------------------8<----------------
screen -x <localsessionname> -X screen 'ssh hostN "screen -dmS
<sessionname>;screen -x <sessionname> -X screen <command>"'
screen -x <localsessionname> -X stuff <password>
------------------------->8-------------------------->8----------------

and if you like the idea of running all ssh in one local screen, you can
put all commands in your .screenrc (and use your favorite language to
modify <command> or get <command> from argv).

-------------------------8<--------------------------8<----------------
screen 'ssh host1 "screen -dmS <sessionname>;screen -x <sessionname> -X
screen <command>"'
screen 'ssh host2 "screen -dmS <sessionname>;screen -x <sessionname> -X
screen <command>"'
...
screen 'ssh hostN "screen -dmS <sessionname>;screen -x <sessionname> -X
screen <command>"'
------------------------->8-------------------------->8----------------

> The -X option seems like it's intended for this purpose, but it seems
> to be a no-op. The man page says "Note that this command doesn't work
> if the session is password protected." To my knowledge the session is
> not password protected, but perhaps I am misunderstanding this.

well, it's just about ^a:password

> Is there some simple recipe for using ssh to execute a command in a
> detached screen on another host?

hope it helps

cheers,

-- 
Guyzmo