Unable to install files with apt-get: "unable to locate package" [duplicate]

I'm having issues with my ubuntu server version 12.04 installed on a HP550 laptop, when i try sudo apt-get install <programname>, e.g apache2 it will not work, saying E: Unable to locate package apache2.

I have tried to look/edit the sources. but they will not work either the gedit command is broken too, i am trying gedit /etc/apt/sources.list for those wondering, is this a case of the computer network not configured properly? it downloaded a language pack easily enough in the installation though. how do i fix this? a prompt reply would be appreciated.

Try running sudo apt-get update before trying to install the package. After installation the system doesn't have an up-to-date package list so you won't be able to find the package.

Once you've done this you should be able to install as normal.

Check your /etc/apt/sources.list

This is an example sources.list file. I have used the program net-select-apt to chose the fastest mirror for me. Also, notice this is for 12.04/Precise.

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://mirror.symnds.com/ubuntu/ precise main restricted
deb-src http://mirror.symnds.com/ubuntu/ precise main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://mirror.symnds.com/ubuntu/ precise-updates main restricted
deb-src http://mirror.symnds.com/ubuntu/ precise-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://mirror.symnds.com/ubuntu/ precise universe
deb-src http://mirror.symnds.com/ubuntu/ precise universe
deb http://mirror.symnds.com/ubuntu/ precise-updates universe
deb-src http://mirror.symnds.com/ubuntu/ precise-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://mirror.symnds.com/ubuntu/ precise multiverse
deb-src http://mirror.symnds.com/ubuntu/ precise multiverse
deb http://mirror.symnds.com/ubuntu/ precise-updates multiverse
deb-src http://mirror.symnds.com/ubuntu/ precise-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://mirror.symnds.com/ubuntu/ precise-backports main restricted universe multiverse
deb-src http://mirror.symnds.com/ubuntu/ precise-backports main restricted universe multiverse

deb http://mirror.symnds.com/ubuntu/ precise-security main restricted
deb-src http://mirror.symnds.com/ubuntu/ precise-security main restricted
deb http://mirror.symnds.com/ubuntu/ precise-security universe
deb-src http://mirror.symnds.com/ubuntu/ precise-security universe
deb http://mirror.symnds.com/ubuntu/ precise-security multiverse
deb-src http://mirror.symnds.com/ubuntu/ precise-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu precise partner
deb-src http://archive.canonical.com/ubuntu precise partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu precise main
deb-src http://extras.ubuntu.com/ubuntu precise main

Update your apt

sudo apt-get update

Check if apt can find apache2

sudo apt-cache search apache2

Install apache2

sudo apt-get install apache2

Optional additional repositories

Here are a few optional repos you can go ahead and add to the bottom of your sources.list.

#Chromium
deb http://ppa.launchpad.net/chromium-daily/stable/ubuntu precise main
deb-src http://ppa.launchpad.net/chromium-daily/stable/ubuntu precise main

Yes try writing sudo apt-get update This will download the source package list. apache2 would be on that updated list