Пишу сам для себе, бо постійно забуваю :) .
lsb_release -a
lufa@ts:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04 LTS
Release: 12.04
Codename: precise
cat /etc/issue.net (/etc/issue)
lufa@ts:~$ cat /etc/issue.net
Ubuntu 12.04 LTS