When listing the content of the dirctory /lib/modules I see a list of generic-pae directories (Ubuntu 12.04): drwxr-xr-x 4 root root 4096 Apr 23  2012 3.2.0-23-generic-paedrwxr-xr-x 5 root root 4096 Nov 20  2012 3.2.0-27-generic-paedrwxr-xr-x 5 root root 4096 Nov 20  2012 3.2.0-29-generic-paedrwxr-xr-x 5 root root 4096 Nov 20  2012 3.2.0-30-generic-paedrwxr-xr-x 5 root root 4096 Nov 20  2012 3.2.0-31-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-32-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-33-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-34-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-35-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-36-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-37-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-38-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-39-generic-paedrwxr-xr-x 5 root root 4096 May 16  2013 3.2.0-41-generic-paedrwxr-xr-x 5 root root 4096 Jun 18 08:26 3.2.0-48-generic-paedrwxr-xr-x 5 root root 4096 Oct  3 07:47 3.2.0-54-generic-paeWhat are all of these directories? What is their content? Can I remove the ones with a lower number, because they take up quite a lot of space?
What are the generic-pae directories in /lib/modules?
ubuntu;kernel modules;libraries