e package libauthen-pam-perl has no installation candidate

This means of all the repositories listed in your software sources, none of them have the package named munin-memcached. It then downloads the package from that repo. Then when you try to install any package, apt checks the package name in it's database, finds it and checks the name of the repo from where it got it. When you add software sources and then do an apt-get update your system APT's database is updated with all the packages on the repositories listed in software sources list. This happens when you are trying to install a package about which APT does not have any idea. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package munin-memcached has no installation candidate I googled for the problem and someone said to do a apt-get upgrade but it still did not solve my problem. Done Package munin-memcached is not available, but is referred to by another package.

Done Building dependency tree Reading state information. What does the above Error mean? What is an installation candidate? I was trying to do sudo apt-get install munin-memcached and I get this message: Reading package lists.

Virtualbox-guest-x11 Has No Installation Candidate.

Fail webmin install, E: Package webmin has no installation candidate. Does anyone know how to install libauthen-pam-perl. E: Package libauthen-pam-perl has no installation. Installing Webmin on Ubuntu Linux (Server edition).

E package libauthen-pam-perl has no installation candidate