what are the safest software sources?

[iMac71]

No; this should be enough:

sudo apt-get install ppa-purge

Sure, first of all I have to install ppa-purge as shown by you, but then? I think I should use the command I wrote in my previous post for purging all unwanted ppas, don't I?

[Pjotr123]

Sure, first of all I have to install ppa-purge as shown by you, but then? I think I should use the command I wrote in my previous post for purging all unwanted ppas, don't I?

Possibly; I've never needed to use it myself.... You can read the manual:

man ppa-purge

[iMac71]

Possibly; I've never needed to use it myself.... You can read the manual:

man ppa-purge

from the online manual page of ppa-purge: it

provides a bash shell script capable of automatically downgrading all packages in a given PPA back to the ubuntu versions.

So, thanks to your suggestions and to the ones of the other forum users, I won't need to make a clean install, but I'll have only to use ppa-purge for all unwanted ppas.

[zombifier25]

This is still extreme paranoia IMO. You only use two PPAs that are pretty much well-known, trusted, tested, etc. etc.. I use about a dozen.

Makes me think you should be using Debian Stable

[Zill]

Makes me think you should be using Debian Stable

...but the current Stable (squeeze) will superseded very shortly by the current Testing (wheezy).

• DebianWheezy

[iMac71]

This is still extreme paranoia IMO.

you might be right...

Makes me think you should be using Debian Stable

unfortunately Debian seems not to work properly on my iMac .