Re: I don't understand the new aptitude
On Tue, May 22, 2007 at 11:03:47AM +0200, Dan H <dunno@stoptrick.com> was heard to say:
> I can't get my head around the (as of etch) newfangled aptitude
> dependency handling procedure. As an example, I'm trying to install
> texlive. As soon as I hit '+', I see this cryptic message in the bottom
> line:
>
> [1(1)/...] Suggest 2 installs, 4 keeps
> w: examine !: apply ...
>
> (...and I just noticed I had to copy that by hand because aptitude
> --and only aptitude!-- seems to disallow copying text from the xterm
> it's running in! What kind of sadism is that?)
This is because aptitude asks xterm to send it mouse events, as do
other programs (links and w3m come to mind). Since aptitude is getting
the mouse events, xterm can't use them to copy & paste.
You can still select text while aptitude is running by holding down
shift while you click.
> Anyway, when I type '!', thinking that aptitude will now do what it
> suggests, namely install stuff, all the to-be-installed things are
> deselected and nothing happens.
>
> So maybe 'e'xamining things will tell me stuff. When I do that, I see
> lists of packages that could be "kept" at their current versions (which
> doesn't make sense because they are flagged "UNINST". I also see
> lists of packages to be installed. Anyway, as soon as I hit '!'
> everything goes away again. I also can scroll through many alternatives
> using '.' and ',' but I don't really understand what this is all about.
That's interesting. Could you say which packages are broken and
which ones aptitude says it wants to install / keep? This might be
a bug. It would also be interesting to see what you get when you
press "o" to get a breakdown of why the resolver did what it did.
The resolver information screen lists as "kept" packages packages
whose upgrade or installation is going to be cancelled. It might be
that aptitude decided to cancel installing texlive for some reason,
which would cancel installing all the stuff it depends on (unfortunately,
the removal of unused packages doesn't integrate with the resolver). My
guess is that aptitude can't find any resolution that includes texlive;
you could verify this by pressing "r" while the "keep texlive at its
current version" option is selected, then seeing what the next new
solution is.
My usual procedure using the resolver is to hit "e" to pop into the
resolution screen and examine the decision aptitude made. You can
select the individual actions in the list it presents to see why it made
each decision (in the lower pane of the display).
I tag the decisions it made that I don't like by pressing "r", then
ask it for the next solution; lather, rinse, repeat until I'm satisfied.
If I'm not satisfied after looking at a few solutions, I might resolve
things by hand, or just take the first solution (which usually errs on
the side of being too conservative). You apply the solution by pressing "!".
In some cases "a" can also be useful; it tells aptitude to take an
action whenever possible. This is partiularly useful (IMO) combined
with tabbing into the list of alternative choices that shows up in
the lower pane of the solution view.
Daniel
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