I get this result on my newly installed ubuntu 9.04 netbook remix. I haven't tampered with any apt files at all. It doesnt work for any other packages.
ira@ira-windu100:/etc/apt$ sudo apt-get install git.core
[sudo] password for ira:
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package git.core
ira@ira-windu100:/etc/apt$
You should first search git packages (git.core package doesn't exists)
apt-cache search git --names-only
When you search an un-installed package, you can run :
sudo apt-file search git-core
To install it, simply run :
sudo apt-get install apt-file
In the present case, you just have to run :
sudo apt-get install git
Last but not least, you should run
sudo apt-get update
like Oliver Salzburg said.
9.04 reached end of life in October of 2010; you need to install a supported release.
As Psusi said, Ubuntu 9.04 is no longer supported. If you really need to use it, you can change your /etc/apt/sources.list to something like:
deb http://old-releases.ubuntu.com/ubuntu/ jaunty main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ jaunty-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ jaunty-security main restricted universe multiverse
Then just apt-get update && apt-get install git-core. You'll probably want to upgrade to a supported release. Follow the directions at https://help.ubuntu.com/community/EOLUpgrades/Jaunty
sudo apt-get update?