Update in 14.04 LTS

The update from Ubuntu 14.04 to 14.04.1 to 14.04.2 and so on is performed automatically when you perform the recommended updates with the help of update-manager, if you have the trusty-updates repository enabled.

Please provide the output of the following diagnostic commands (to be executed in a terminal window)

uname -a
lsb_release -crid
cat -n /etc/apt/sources.list

inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$ uname -a
Linux inderjit-300E4A-300E5A-300E7A-3430EA-3530EA 3.16.0-59-generic #79~14.04.1-Ubuntu SMP Mon Jan 18 15:41:27 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$ lsb_release -crid
Distributor ID: Ubuntu
Description: Ubuntu 14.04.3 LTS
Release: 14.04
Codename: trusty
inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$ cat -n /etc/apt/sources.list^C
inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$

inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$ uname -a
Linux inderjit-300E4A-300E5A-300E7A-3430EA-3530EA 3.16.0-59-generic #79~14.04.1-Ubuntu SMP Mon Jan 18 15:41:27 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$ lsb_release -crid
Distributor ID: Ubuntu
Description: Ubuntu 14.04.3 LTS
Release: 14.04
Codename: trusty
inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$ cat -n /etc/apt/sources.list^C
inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$ cat -n /etc/apt/sources.list
     1 # deb cdrom:[Ubuntu 14.04.2 LTS _Trusty Tahr_ - Release amd64 (20150218.1)]/ trusty main restricted
     2
     3 # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
     4 # newer versions of the distribution.
     5 deb http://in.archive.ubuntu.com/ubuntu/ trusty main
     6 deb-src http://in.archive.ubuntu.com/ubuntu/ trusty main
     7
     8 ## Major bug fix updates produced after the final release of the
     9 ## distribution.
    10 deb http://in.archive.ubuntu.com/ubuntu/ trusty-updates main
    11 deb-src http://in.archive.ubuntu.com/ubuntu/ trusty-updates main
    12
    13 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
    14 ## team. Also, please note that software in universe WILL NOT receive any
    15 ## review or updates from the Ubuntu security team.
    16 deb http://in.archive.ubuntu.com/ubuntu/ trusty universe
    17 deb-src http://in.archive.ubuntu.com/ubuntu/ trusty universe
    18 deb http://in.archive.ubuntu.com/ubuntu/ trusty-updates universe
    19 deb-src http://in.archive.ubuntu.com/ubuntu/ trusty-updates universe
    20
    21 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
    22 ## team, and may not be under a free licence. Please satisfy yourself as to
    23 ## your rights to use the software. Also, please note that software in
    24 ## multiverse WILL NOT receive any review or updates from the Ubuntu
    25 ## security team.
    26
    27 ## N.B. software from this repository may not have been tested as
    28 ## extensively as that contained in the main release, although it includes
    29 ## newer versions of some applications which may provide useful features.
    30 ## Also, please note that software in backports WILL NOT receive any review
    31 ## or updates from the Ubuntu security team.
    32
    33 deb http://security.ubuntu.com/ubuntu trusty-security main
    34 deb-src http://security.ubuntu.com/ubuntu trusty-security main
    35 deb http://security.ubuntu.com/ubuntu trusty-security universe
    36 deb-src http://security.ubuntu.com/ubuntu trusty-security universe
    37
    38 ## Uncomment the following two lines to add software from Canonical's
    39 ## 'partner' repository.
    40 ## This software is not part of Ubuntu, but is offered by Canonical and the
    41 ## respective vendors as a service to Ubuntu users.
    42 deb http://archive.canonical.com/ubuntu trusty partner
    43 deb-src http://archive.canonical.com/ubuntu trusty partner
    44
    45 ## This software is not part of Ubuntu, but is offered by third-party
    46 ## developers who want to ship their latest software.
    47 # deb http://extras.ubuntu.com/ubuntu trusty main
    48 # deb-src http://extras.ubuntu.com/ubuntu trusty main
inderjit@inderjit-300E4A-300E5A-300E7A-3430EA-3530EA:~$

See your output

"Description: Ubuntu 14.04.3 LTS"

You are running 14.04.3.

Thanks actionparsnip, that solved my question.