How can I find the version of Ubuntu that is installed?

Your version of Ubuntu can be determined by opening System Settings and then opening the System Info or Details (from 12.04) section:

This page will also tell you whether you have the 32- or 64-bit version of Ubuntu installed, as well as what processor and graphics you have, the amount of RAM installed, and your disk capacity.

You can get this info from a terminal with the command:

lsb_release -a

Credit in part to htorque and WarriorIng64

[Note: for versions before 11.10, e.g. 11.04 this is not available this way, but see Roland's answer below for workable option (basically use the 'System Monitor' icon instead]

Apart from:

• lsb_release -a and

• cat /etc/*release ,

you can also see the version in the GNOME System Monitor (press Alt + F2, type gnome-system-monitor, and hit Enter):

In Ubuntu 11.10 onwards, the version of Ubuntu installed can be found by entering System Settings > System Info (in newer versions like 14.04 LTS, this tab might be called Details instead):

This page will also tell you whether you have the 32- or 64-bit version of Ubuntu installed, as well as what processor and graphics you have, the amount of RAM installed, and your disk capacity.

$ lsb_release -r
Release:        10.04

$ lsb_release -c
Codename:       lucid

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 10.04.2 LTS
Release:        10.04
Codename:       lucid

$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=10.04
DISTRIB_CODENAME=lucid

"LSB" means Linux Standard Base, a joint project of several Linux distributions. Its goal is to develop and promote a set of open standards that will increase compatibility among Linux distributions.

Quite a few ways -

On the command line:

1. lsb_release -a ▸ exact release name, version, etc.
2. cat /etc/issue ▸ formal release name
3. cat /etc/issue.net ▸ cleaner version of previous one
4. cat /etc/debian_version ▸ will give you the Debian code name
5. cat /proc/version ▸ will give you quite a lot of information about your kernel, when was it compiled, which GCC version has been used, etc.
6. uname -a ▸ will tell you about your kernel information, plus architecture (i386 ▸ 32 bit, x86_64 ▸ 64 bit)

If you like a GUI more than the command line, the System page on System Monitor gnome-system-monitor application should give you more than enough information. Release name, architecture variant, cores in the system, RAM available, and the space available on the root file system.

The command to find ubuntu version is,

lsb_release -a

or

cat /etc/lsb-release

or

System > About Ubuntu

You can check it via command line.

1. Open a Terminal by pressing Ctrl+Alt+T.

2. Type:

   lsb_release -a
   

   and press Enter.

3. The Ubuntu version is displayed on the 'Description:' line.

For more details, see here.

If additionally to the version you want to find out your Ubuntu flavor, run the following:

cat /var/log/installer/media-info 

The output should be something like:

Xubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)

If you also want to be sure about your Desktop Environment, type:

echo $XDG_CURRENT_DESKTOP

The output should be something like:

XFCE

There are GUI ways of checking but I prefer the Terminal.

To check your Ubuntu version using the command line:

1. Open a Terminal by pressing Ctrl+Alt+T.
2. Type: lsb_release -a and press Enter.

The Ubuntu version is displayed on the 'Description:' line.

References:

Identifying the version of Ubuntu you are using.

This command will also find your installed Ubuntu version,

awk '/^Description: Ubuntu [0-9]/ {print "Ubuntu",$3; exit;}' /usr/share/python-apt/templates/Ubuntu.info

Example:

$ awk '/^Description: Ubuntu [0-9]/ {print "Ubuntu",$3; exit;}' /usr/share/python-apt/templates/Ubuntu.info
Ubuntu 14.04