$ cat /proc/version
Linux version 2.6.32-504.3.3.el6.x86_64 (mockbuild@x86-028.build.eng.bos.redhat.com) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-9) (GCC) ) #1 SMP Fri Dec 12 16:05:43 EST 2014

$ lsb_release -a
LSB Version:    :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch
Distributor ID: RedHatEnterpriseServer
Description:    Red Hat Enterprise Linux Server release 6.6 (Santiago)
Release:        6.6
Codename:       Santiago

$ cat /etc/redhat-release
Red Hat Enterprise Linux Server release 6.6 (Santiago)

$ cat /etc/debian_version 
8.0

$ cat /usr/lib/os-release
PRETTY_NAME="Debian GNU/Linux 8 (jessie)"
NAME="Debian GNU/Linux"
VERSION_ID="8"
VERSION="8 (jessie)"
ID=debian
HOME_URL="http://www.debian.org/"
SUPPORT_URL="http://www.debian.org/support/"
BUG_REPORT_URL="https://bugs.debian.org/"

Voir aussi /etc/system-release