Re: Understanding package dependencies

[Greg Wooledge <greg@wooledge.org>]

On Sat, Oct 07, 2023 at 07:24:24PM +0200, Steve Keller wrote:
> Greg Wooledge <greg@wooledge.org> writes:
> 
> > Package: sysvinit-utils
> > [...]
> > Provides: lsb-base (= 11.1.0)
> >
> > When you remove the physical lsb-base package, the virtual package
> > provided by sysvinit-utils remains, to satisfy the dependencies of
> > ntpsec, rsync, etc.
> 
> OK, that explains, why lsb-base can be removed without ntpsec. Is there
> a way to search for "Provides" in packages? I.e. show me all packages
> (installed or all) that provide some feature "foobar"?

I couldn't find one within a minute or so of looking, so I simply
searched for "Provides:.*lsb-base" in /var/lib/dpkg/status.

Now that I've had a bit more time to ponder it, I recall that there's
"apt-cache showpkg".  It's not intuitive or easy to remember, but....

unicorn:~$ apt-cache showpkg lsb-base
Package: lsb-base
[... LOTS of useless info ...]
Dependencies: 
11.6 - sysvinit-utils (2 3.05-4~) 
Provides: 
11.6 - lsb-base:i386 (= 11.6) 
Reverse Provides: 
sysvinit-utils:i386 3.06-4 (= 11.1.0)
sysvinit-utils 3.06-4 (= 11.1.0)