Ubuntu

=> 14.04

$ uname -a
Linux [hostname] 3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:28:38 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.1 LTS
Release:    14.04
Codename:   trusty

$ cat /etc/issue.net 
Ubuntu 14.04.1 LTS

=> 13.10

$ uname -a
Linux localhost 3.11.0-3-generic #8-Ubuntu SMP Fri Aug 23 16:49:15 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/issue.net
Ubuntu Saucy Salamander (development branch)

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu Saucy Salamander (development branch)
Release:    13.10
Codename:   saucy

=> 13.04

$ cat /etc/issue.net
Ubuntu 13.04

$ uname -a
Linux Desktop 3.8.0-35-generic #50-Ubuntu SMP Tue Dec 3 01:24:59 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

=> 12.04

$ cat /etc/issue.net
Ubuntu 12.04.3 LTS

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 12.04.2 LTS
Release:    12.04
Codename:   precise

=> 11.04

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 11.04
Release: 11.04
Codename: natty

=> 10.04

$ uname -a
Linux [hostname] 2.6.32-24-generic #38-Ubuntu SMP Mon Jul 5 09:22:14 UTC 2010 i686 GNU/Linux

$ cat /etc/issue.net
Ubuntu 10.04.4 LTS

$ lsb_release -a
Distributor ID: Ubuntu
Description:    Ubuntu 10.04.1 LTS
Release:    10.04
Codename:   lucid

---

Linux Mint

=> 17

$ cat /etc/issue.net
Linux Mint 17 Qiana

$ cat /etc/lsb-release
DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=17
DISTRIB_CODENAME=qiana
DISTRIB_DESCRIPTION="Linux Mint 17 Qiana"

=> 16

$ cat /etc/issue.net
Linux Mint 16 Petra

$ cat /etc/lsb-release
DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=16
DISTRIB_CODENAME=petra
DISTRIB_DESCRIPTION="Linux Mint 16 Petra"

=> 15

Mate

$ cat /etc/linuxmint/info
RELEASE=15
CODENAME=olivia
EDITION="MATE 64-bit"
DESCRIPTION="Linux Mint 15 Olivia"
DESKTOP=MATE

Cinnamon

$ cat /etc/linuxmint/info
RELEASE=15
CODENAME=olivia
EDITION="Cinnamon 64-bit"
DESCRIPTION="Linux Mint 15 Olivia"
DESKTOP=Gnome

=> 14

$ cat /etc/issue.net
Linux Mint 14 Nadia

=> 13

$ cat /etc/linuxmint/info
RELEASE=13
CODENAME=maya
EDITION="Cinnamon 32-bit"
DESCRIPTION="Linux Mint 13 Maya"
DESKTOP=Gnome

=> 9

$ cat /etc/linuxmint/info 
RELEASE=9
CODENAME=isadora
EDITION="Gnome 32-bit"
DESCRIPTION="Linux Mint 9 Isadora"
DESKTOP=Gnome

=> 1 (?)

$ lsb_release -a
No LSB modules are available.
Distributor ID:   LinuxMint
Description:   LMDE Xfce Edition
Release:   1
Codename:   debian

$ lsb_release -a
No LSB modules are available.
Distributor ID:   LinuxMint
Description:   Linux Mint Debian Edition
Release:   1
Codename:   debian

---

Debian

=> 7

$ cat /etc/issue.net
Debian GNU/Linux 7.0

$ lsb_release -a
No LSB modules are available.
Distributor ID:   Debian
Description:   Debian GNU/Linux 7.0 (wheezy)
Release:   7.0
Codename:   wheezy

=> 6

$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux 6.0.6 (squeeze)
Release:    6.0.6
Codename:   squeeze

$ cat /etc/issue.net
Debian GNU/Linux 6.0

$ lsb_release -a
No LSB modules are available.
Distributor ID:   Debian
Description:   Debian GNU/Linux 6.0.5 (squeeze)
Release:   6.0.5
Codename:   squeeze

---

Red Hat Enterprise Server

=> 6.2

$ uname -a
Linux [hostname] 2.6.32-220.el6.x86_64 #1 SMP Wed Nov 9 08:03:13 EST 2011 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/issue.net
Red Hat Enterprise Linux Server release 6.2 (Santiago)
Kernel \r on an \m

$ lsb_release -a
LSB Version:    :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 6.2 (Santiago)
Release:        6.2
Codename:       Santiago

=> 5.6

$ uname -a
Linux srs759 2.6.18-238.el5 #1 SMP Sun Dec 19 14:22:44 EST 2010 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/issue.net
Red Hat Enterprise Linux Server release 5.6 (Tikanga)
Kernel \r on an \m

$ lsb_release -a
LSB Version:    :core-4.0-amd64:core-4.0-ia32:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-ia32:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-ia32:printing-4.0-noarch
Distributor ID: RedHatEnterpriseServer
Description:    Red Hat Enterprise Linux Server release 5.6 (Tikanga)
Release:        5.6
Codename:       Tikanga

=> 5.5

$ uname -a
Linux [hostname] 2.6.18-194.el5 #1 SMP Tue Mar 16 21:52:39 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/issue.net
Red Hat Enterprise Linux Server release 5.5 (Tikanga)
Kernel \r on an \m

$ lsb_release -a
LSB Version:    :core-3.1-amd64:core-3.1-ia32:core-3.1-noarch:graphics-3.1-amd64:graphics-3.1-ia32:graphics-3.1-noarch
Distributor ID: RedHatEnterpriseServer
Description:    Red Hat Enterprise Linux Server release 5.5 (Tikanga)
Release:        5.5
Codename:       Tikanga

=> 5.1

# lsb_release -a
LSB Version:    :core-3.1-ia32:core-3.1-noarch:graphics-3.1-ia32:graphics-3.1-noarch
Distributor ID: RedHatEnterpriseServer
Description:    Red Hat Enterprise Linux Server release 5.1 (Tikanga)
Release:        5.1
Codename:       Tikanga

---

CentOS

=> 6.5

$ uname -a
Linux [hostname] 2.6.32-431.1.2.0.1.el6.i686 #1 SMP Fri Dec 13 11:45:23 UTC 2013 i686 i686 i386 GNU/Linux

$ cat /etc/issue.net 
CentOS release 6.5 (Final)
Kernel \r on an \m

$ lsb_release -a
-bash: lsb_release: command not found

=> 6.4

# 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: CentOS
Description:    CentOS release 6.4 (Final)
Release:        6.4
Codename:       Final

---

ArchLinux

$ lsb_release -a
LSB Version: n/a 
Distributor ID: archlinux 
Description: Arch Linux 
Release: rolling 
Codename: n/a

---

CrunchBang

$ cat /etc/issue.net
CrunchBang Linux waldorf

---

Oracle

=> 5.7

# cat /etc/issue.net (and 'head -1')
Oracle Linux Server release 5.7

=> 5.4

$ lsb_release -a
LSB Version: :core-3.1-amd64:core-3.1-ia32:core-3.1-noarch:graphics-3.1-amd64 :graphics-3.1-ia32:graphics-3.1-noarch
Distributor ID: EnterpriseEnterpriseServer
Description: Enterprise Linux Enterprise Linux Server release 5.4 (Carthage)
Release: 5.4
Codename: Carthage