Re: safe to purge older versions of installed software?

[Dean Sutherland <dean@codemonkies.net>]

On Sat, 22 Aug 2009 05:45:00 -0400 (EDT), rpjday@crashcourse.ca wrote:

[snip]
> >
> >   no, i want to go the *other* way -- to ask what
> > currently-installed packages depend *on* a given,
> > currently-installed package.
> 
>   actually, even though i was asking in the context of a system in the
> process of upgrading on which there is all kinds of historical cruft
> so i fully expect to find older versions of packages lying around, i
> just noticed that the same thing happens on a fresh (and updated)
> version of lenny (5.0.2).
> 
>   here are two currently installed packages (according to "dpkg -l"):
> 
>     gcc-4.2-base
>     gcc-4.3-base
> 
> my immediate thought is -- why do i need both?  it's quite possible i
> *do*, but i don't know how to verify that.  hence my question:  how
> can i display what installed packages allegedly depend on
> gcc-4.2-base, so that i know it's actually required to be on my
> system.  i realize i can simulate trying to remove it to see what
> would happen, but that strikes me as messy and overkill.
> 


Hi,

Someone correct me if I'm wrong, but I believe the command you're
after is apt-cache rdepends packagename

dean@subspace:~$ apt-cache rdepends gcc-4.1
gcc-4.1
Reverse Depends:
  linux-headers-2.6.26-1-686
  gcc-doc-base
  gcc-doc-base
  gcc-4.1-doc
  gcc-4.1-doc
  gpc-4.1
  gcj-4.4-jdk
  gcj-4.3
  gcj-4.2
  gcc-4.1-multilib
  gcc-4.1-multilib
  gcc-4.1-locales
  g++-4.1

It appears not all of those packages will be removed if you remove the
gcc-4.1 package.

dean@subspace:~$ sudo apt-get remove gcc-4.1-base
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be REMOVED:
  cpp-4.1 gcc-4.1 gcc-4.1-base linux-headers-2.6.26-1-686
0 upgraded, 0 newly installed, 4 to remove and 394 not upgraded.


--
Dean Sutherland