To check for this possibility run the following command: rmadison For example, qt4-default has been discontinued from the default repositories in Ubuntu 20.04 and later. One possible reason for this message is that this package is an old package that has been discontinued from your release's default repositories. What does Package has no installation candidate means that the package is not found in your Ubuntu releases software sources.
To install package munin-memcached, issue the below command: sudo apt-get update & sudo apt-get install munin-memcached To add the PPA, issue the below command: sudo add-apt-repository ppa:chris-lea/munin-plugins I checked again and it is not available in official Ubuntu repos.Īfter a bit of googling I found that it is available in this PPA: chris-lea/munin-pluginsĪdd this PPA and install the packages at your own risk. 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, you need to do an apt-get update so that your system APT's database is updated with all the packages on the repositories listed in the software sources lists. This happens when you try to install a package about which APT does not have any idea.