launchpad development
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 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 $LP_USER_1 $LP_USER_2 >> /path/to/.ssh/authorized_keys
Tips:
Add to ~/.screenrc for better color handling term screen-256color
References:
