Cannot install packages in Lubuntu 12.04 [duplicate]

Question

I've just installed lubuntu 12.04 on an Acer aspire one netbook. I've noticed that although chromium-browser is installed, it doesn't come with a flash-player. I tried to install it using

sudo apt-get install flashplugin-installer

but I get the error

E: Unable to locate package flashplugin-installer

I also tried to install some other basic packages like gedit, deluge, kate, geany but I get the same error. Then I tried to update all repositories using

sudo apt-get update && sudo apt-get upgrade

but while it's running there are some errors like

Err http://gr.archive.ubuntu.com quantal-updates/main Sources
404  Not Found

or

W: Failed to fetch http://gr.archive.ubuntu.com/ubuntu/dists/quantal/restricted/source/Sources 404 Not Found

Why is this happening? I've checked my internet connection and it's fine. I also tried to install chrome using GDebi package installer` but I get an error

Dependency is not satisfiable : libnns3(>=3.14.3)

I believe that somehow I cannot see the repositories. What can I do to fix this?

Answer 1

I think the reason is that as of April, Quantal (12.10) has reached end of life and is no longer supported in the main Ubuntu package repositories. However I don't know why it's trying to install a Quantal package on a Precise system. This might be of use but I'd want to check first that your precise sources aren't touched by sed (sorry, sed's not my area):

How to install software or upgrade from an old unsupported release?

Answer 2

Try resetting your configuration files with sudo apt-get -o dpkg::options::="--force-confnew" -o dpkg::options::="--force-confmiss" --reinstall install PAKET

If this does not help, open your sources.list file with sudo gedit /etc/apt/sources.list and try commenting this part out http://gr.archive.ubuntu.com/ubuntu/dists/quantal/restricted/source/Sources using a "#" in front of the line.

After changing your sources.list file, save it update your sources.