How to revert from 14.04 back to 12.04
2136
How to roll back Ubuntu to a previous version?
1520
How to install software or upgrade from an old unsupported release?
111573
What's the best way to re-enable PPAs/repos after an upgrade?
98421
How will people upgrade from 12.10 to later releases after 13.04 is EOL?
120
How do I restore the default repositories?
67827
How to restore the new 14.04-lockscreen
156202
backports reversed debian
20399
How do I upgrade from 14.04 LTS to 16.04.1 LTS?
83960
How do I change my update server in Ubuntu 18.04?
67481
How to revert a do-release-upgrade?
63176
How can I update to Ubuntu 21.04?
119334
How to set Python back to the original version
28172
I want to downgrade from Yosemite 10.10 to Mavericks or previous operating system
55211
Problem when upgrading to Ubuntu 14.04 from Ubuntu 12.04
78859
How to reinstall default packages
119595
Is it necessary to upgrade to 14.04 LTS or can I stand in 12.04 LTS forever with no problem?
89166
How to downgrade Kernel