[Jailkit-users] Screen in jailkit

[dev]

Hello, 

I've been experimenting with getting screen to work in a jail created by 
jailkit. After two hours of experiments and consulting a "big search engine" 
I have been successful.
I still believe my solution is neither the 'best thing' nor is it probably 
very secure. So without further ado, here is how to get screen working in 
debian 4.0r1 (minimal installation) - this may or may not work on other 
linux distributions: 

1. Extend /etc/jailkit/jk_init.ini with: 

[screen]
comment = files and devices for screen
groups = tty
executables = /usr/bin/screen, /usr/bin/dircolors
paths_w_owner = /usr/share/terminfo, /dev/pts, /var/run/screen
devices = /dev/ptypa, /dev/ttypa, /dev/ptmx, /dev/null 

2. Create a jail directory (or use an exisiting directory). See 
http://olivier.sessink.nl/jailkit/howtos_chroot_shell.html 

Use the definition from 1 to extend your jail
"jk_init -v /home/jail screen" 

2b. Now you could start screen, but read the next few steps 

3. Start screen. The first error: "Must be connected to a terminal"
This - possibly dangerous - solution: mount devpts into the jail:
"mount -t devpts devpts /home/jail/dev/pts/" 

4. The next error from screen is "Please set a terminal type". This can be 
circumvented by running "export TERM=xterm" in your chroot session. 

5. Next up is "Directory '/var/run/screen' must have mode 777". So "chmod 
777 /home/jail/var/run/screen". You are probably not logging into the chroot 
with the user root, so you have to correct this from outside your chroot 
session. 

6. This is it: screen should be working inside your jail. 

7. There is only one slight problem up to now: Each time you reconnect to 
your machine using ssh, you'd have to re-export the environment variable 
TERM.
You can edit /home/jail/home/${myuser}/.bashrc and add
"export TERM=xterm" to the end of that file. Now it is set each time you log 
into the jail. 

Any suggestions are very welcome. 

Cheers,
Stephen