Can i upgrade ubuntu without losing my apps and files?

Solution 1:

Yes, you can. However, the restriction is the versions you can upgrade to.

Ubuntu's versioning scheme is that 12.04 and 14.04 are LTS releases and are supported for a longer period of time than non-LTS releases, which are the releases inbetween (12.10, 13.04, 13.10). Due to support length changes before 13.04 was released, the current supported non-LTS releases are 12.10 and 13.10 (13.04 has reached End-Of-Life).

As for upgrading, you cannot directly upgrade from 12.04 (LTS) to 13.04 (non-LTS) (nor can you upgrade to 13.04 in any way, since it is EOL); You will have to go through 12.10, and then jump to 13.10. Usually, for non-LTS releases, you have to go through each version inbetween.

However, you will be able to upgrade directly from 12.04 (LTS) to 14.04 (LTS) when 14.04 is released.