= Notes on using screen to collaborate =

Scenario:
 * Alice wants to collaborate with Bob.  
 * Her home network is called alice.net and she has two machines, edge and dev.  
 * Port 22 on alice.net is open and forwards to edge.  
 * Dev is not exposed through her router.  It is the machine where she does her work and wants to allow collaboration.
 * Alice wants to use {{{screen}}} to share a terminal session with Bob.

Setup:
 * On edge Alice creates a user account ''guest'' that will be used by Bob.  
 * Alice does the following to create a reverse tunnel from dev to edge:
    {{{ssh -N -R '*:2200:localhost:22' edge}}}
 * Bob will be connecting to port 2200 so Alice must open that port on her router and forward it to edge.
 * To use screen in multiuser mode, it must run as root with setuid.  Alice must do the following on dev:
    * {{{sudo chmod +s /usr/bin/screen}}}
    * {{{sudo chmod 755 /var/run/screen}}}

Sharing a screen:
 * Alice starts screen {{{screen -S shared}}}.  She then does the required configuration:
    * {{{ctl-a :multiuser on}}}
    * {{{ctl-a :acladd guest}}}
 * Bob connects by using {{{ssh -p 2200 guest@alice.net}}}
 * He'll be prompted for the guest user UNIX password.
 * Once logged in he connects to the screen using {{{screen -x alice/shared}}}

Next steps:
 * Get per user credentials to work as shown in the [[https://wiki.canonical.com/InformationInfrastructure/OSA/ScreenSharingWithDevs|LOSA guide]]
   * Our scenario is more complicated in that Alice doesn't want to allow Bob to connect using her account.  She also doesn't want to work in a dumbed-down guest account.  What to do?
   * The user files in a normal SSH set up are in /home/$user/.ssh/authorized_keys, not in /etc/ssh/user-authorized-keys as shown in the LOSA write up.
   * gmb has written a simple script that will grab the SSH keys of a given LP user for you and echo them out to STDOUT:
{{{
bzr --no-plugins cat http://bazaar.launchpad.net/~gmb/+junk/get-lp-ssh-keys/get-lp-ssh-keys.py > /tmp/get-lp-ssh-keys.py
chmod +x /tmp/get-lp-ssh-keys.py
/tmp/get-lp-ssh-keys.py $LP_USER_1 $LP_USER_2 >> /path/to/.ssh/authorized_keys
}}}

Tips:
 * Add to ~/.screenrc for better color handling {{{term screen-256color}}}

References:
 * http://www.pixelbeat.org/docs/screen/