Software update, requires installing packages from unauthenticated sources
12054
How do I deal with "unauthenticated sources" errors in the Software Center?
115722
Apt sources.list problem , packages not found?
73173
How to Fix Broken Packages?
92604
How can I install a package without root access?
17208
What does this apt error message ("Download is performed unsandboxed as root...") mean?
60659
Install newer package version from trusty-backports
134143
How do I know what packages I need to install?
18052
How to remove/install a package that is not fully installed?
5830
How to prevent updating of a specific package?
66915
How to request a package upgrade in the next Ubuntu release
99687
update-alternatives --install says it needs link name path priority?
5242
How to update software installed via .deb file
10633
software updater failed to download repository information
5162
How to fake a package version installed?
54991
How can I install updates and shut down from the command line?
3298
How do I resolve unmet dependencies after adding a PPA?
30754
Cannot update: "No available releases found"