Chrome OS, Linux, and /dev/net/tun

If you use the lovely "Linux Apps" for Chrome OS, you might be a little disappointed when you try to use vpnc or anything that requires /dev/net/tun:

kduda@penguin:~$ sudo vpnc hq
vpnc: can't open /dev/net/tun, check that it is either device char 10 200 or (with DevFS) a symlink to ../misc/net/tun (not misc/net/tun): Permission denied
vpnc: can't initialise tunnel interface: Permission denied
kduda@penguin:~$ ls -l /dev/net/tun
crw------- 1 nobody nogroup 10, 200 Feb  7 02:11 /dev/net/tun
kduda@penguin:~$ 

Oh no!  Now what?

Here is the magic incantation to get this thing to work.  Start crosh (control-alt-T in Chrome).  In crosh:

crosh> vmc start termina

(termina) chronos@localhost ~ $ 

When you get the termina prompt, then click on the Terminal App in the Shelf:

This starts the penguin container with the almost-correct configuration.  The trick is to make the configuration all-the-way correct.  Back to crosh:

(termina) chronos@localhost ~ $ lxc stop -f penguin
(termina) chronos@localhost ~ $ lxc config device add penguin tun unix-char path=/dev/net/tun
Device tun added to penguin
(termina) chronos@localhost ~ $ lxc start penguin
(termina) chronos@localhost ~ $ 

Now, one more click on the Terminal App, and you are all set:

ddddddddddadsfasdfasdfasdfasdfasdfasdfasdfasdfasdfasdfakduda@penguin:~$ ls -l /dev/net/tun
crw-rw-rw- 1 root root 10, 200 Feb  7 02:24 /dev/net/tun
kduda@penguin:~$ 

kduda@penguin:~$ ls -l /dev/net/tun
crw-rw-rw- 1 root root 10, 200 Feb  7 02:24 /dev/net/tun
kduda@penguin:~$ 

Victory!

kduda@penguin:~$ sudo vpnc hq
vpnc: can't open /dev/net/tun, check that it is either device char 10 200 or (with DevFS) a symlink to ../misc/net/tun (not misc/net/tun): Permission denied
vpnc: can't initialise tunnel interface: Permission denied
kduda@penguin:~$ ls -l /dev/net/tun
crw------- 1 nobody nogroup 10, 200 Feb  7 02:11 /dev/net/tun
kduda@penguin:~$ 

kduda@penguin:~$ sudo vpnc hq
vpnc: can't open /dev/net/tun, check that it is either device char 10 200 or (with DevFS) a symlink to ../misc/net/tun (not misc/net/tun): Permission denied
vpnc: can't initialise tunnel interface: Permission denied
kduda@penguin:~$ ls -l /dev/net/tun
crw------- 1 nobody nogroup 10, 200 Feb  7 02:11 /dev/net/tun
kduda@penguin:~$ 

kduda@penguin:~$ sudo vpnc hq
vpnc: can't open /dev/net/tun, check that it is either device char 10 200 or (with DevFS) a symlink to ../misc/net/tun (not misc/net/tun): Permission denied
vpnc: can't initialise tunnel interface: Permission denied
kduda@penguin:~$ ls -l /dev/net/tun
crw------- 1 nobody nogroup 10, 200 Feb  7 02:11 /dev/net/tun
kduda@penguin:~$ 

kduda@penguin:~$ sudo vpnc hq
vpnc: can't open /dev/net/tun, check that it is either device char 10 200 or (with DevFS) a symlink to ../misc/net/tun (not misc/net/tun): Permission denied
vpnc: can't initialise tunnel interface: Permission denied
kduda@penguin:~$ ls -l /dev/net/tun
crw------- 1 nobody nogroup 10, 200 Feb  7 02:11 /dev/net/tun
kduda@penguin:~$ 

kduda@penguin:~$ sudo vpnc hq
vpnc: can't open /dev/net/tun, check that it is either device char 10 200 or (with DevFS) a symlink to ../misc/net/tun (not misc/net/tun): Permission denied
vpnc: can't initialise tunnel interface: Permission denied
kduda@penguin:~$ ls -l /dev/net/tun
crw------- 1 nobody nogroup 10, 200 Feb  7 02:11 /dev/net/tun
kduda@penguin:~$ kduda@penguin:~$ sudo vpnc hq

vpnc: can't open /dev/net/tun, check that it is either device char 10 200 or (with DevFS) a symlink to ../misc/net/tun (not misc/net/tun): Permission denied
vpnc: can't initialise tunnel interface: Permission denied
kduda@penguin:~$ ls -l /dev/net/tun
crw------- 1 nobody nogroup 10, 200 Feb  7 02:11 /dev/net/tun
kduda@penguin:~$ 

kduda@penguin:~$ sudo vpnc hq
vpnc: can't open /dev/net/tun, check that it is either device char 10 200 or (with DevFS) a symlink to ../misc/net/tun (not misc/net/tun): Permission denied
vpnc: can't initialise tunnel interface: Permission denied
kduda@penguin:~$