How to reinstall Ubuntu in the easiest way?

I just want to delete EVERYTHING except maybe /home folder and reinstall everything, because system became a little bit slow and I want to do that when 14.04 comes out. What's the best way to do that?

At the moment I have 12.04 and have some other systems (cinamon, lubuntu etc.) that I want gone.

How you re-install Ubuntu over an existing older version depends on if you have /home in a separate partition or as a folder within / partition, the default.

In either case you start the installation process from a live DVD/USB. Proceed until you come to the Installation Type page.

If you have /home in its default location within / partition:

Choose the option: Upgrade Ubuntu 12.04 LTS to 14.04 LTS. This will keep your /home folder. Even though it says "installed software will be kept where possible," in my experience it cleared most of them. YMMV.

If you have /home in its own separate partition:

You can either go with the above choice.

Or you can choose Something else. If you choose "Something else," make sure you check the format box for the / partition and uncheck the format box for /home partition. See below for an example.

Note, in this picture above both the / and /home partitions are to be formatted. Make sure that the format box for /home is unchecked before you proceed. Otherwise you will lose all your data!

This method will format the / partition and all the extra programs you had installed in the older version will be gone. However, the settings saved in the /home will remain. If you decide to re-install some of them, say Chrome, your personal configuration, if any, should be there for the new installation to use.

Removing Cinamon and Lubuntu

It depends on how you installed Cinamon Lubuntu etc.

If you had installed just the cinamon desktop environments (DE) and the LXDE (the DE for Lubuntu) on top of Ubuntu via Ubuntu Software Center, or the apt-get command, then yes. Either method will delete them.

If you installed these from their own LiveDVD/CD/USB in separate partitions, then no. In that case you will have to remove those partitions first. You can remove these partitions either from the LiveDVD/USB, by choosing the option Try before installing and then using gparted. Make sure you don't delete the wrong partitions. At this stage you can move the other partitions around if needed and reallocate the empty space to the version of Ubuntu you want to keep.

Hope this helps

Just reinstall it over itself.

Ubuntu will not touch your data in /home and you'll start off with a clean slate. Just ensure that "Format" is not selected in your partition screen.

You can reinstall it in the same fashion as you installed:

• How do I install Ubuntu?

Let me reiterate to ensure that you do not reformat your partition! And as with all system upgrades and reinstalls, having a fresh backup is always a good precaution to take.

You might have some things in your home directory that could be leading to performance degradation. In the past I've had config files in my home directory in directories like .gconf and .gnome that ended to get large and unweildy. These days things like that aren't as much of an issue.