[arch-general] First Problem with pacman - Need to understand why

[David C. Rankin]

Aaron Griffin wrote:
> On Wed, Apr 22, 2009 at 2:45 PM, David C. Rankin
> <drankinatty at suddenlinkmail.com> wrote:
>> checking package integrity...
>> (12/12) checking for file conflicts
>> [#############################################] 100%
>> error: could not prepare transaction
>> error: failed to commit transaction (conflicting files)
>> ttf-dejavu: /usr/share/fonts/TTF/DejaVuSans-Bold.ttf exists in filesystem
>> ttf-dejavu: /usr/share/fonts/TTF/DejaVuSans-BoldOblique.ttf exists in filesystem
>> ttf-dejavu: /usr/share/fonts/TTF/DejaVuSans-ExtraLight.ttf exists in filesystem
>>        <snip - remaining dejavu variants>
>> Errors occurred, no packages were upgraded.
>>
>>        And "Yes", DejaVu fonts did exist in /usr/share/fonts/TTF softlinked to
>> /usr/share/fonts/truetype, but why does pacman care? If the same font already
>> exists in a directory, that shouldn't cause the install to blow up -- should it?
> 
> pacman cares because pacman will try it's hardest to never ever break
> your system unless you say so. If pacman has no knowledge of files in
> your system, it'd be amazingly stupid to blindly overwrite them. What
> happens if I wrote a big long OOo document and saved it (stupidly) as
> /usr/bin/mydoc and then pacman decided to install an app named
> "mydoc". Poof, lost my work.
> 
> I know the above is a contrived example, but it serves to illustrate
> the point: pacman is not in control of your system. You are. Pacman
> will never say "I know better than you, so I'll just replace this with
> what I think it should be". Instead it will say "woah woah woah... you
> did something I don't understand. You deal with it and tell me when
> you figured it out"
> 

	That really was a really good "contrived" example, but it makes sense. pacman
is coded to be conservative and doesn't have and way of checking whether what
it is overwriting is a font file or something else and since it isn't a config
file there isn't a md5 hash comparison done to determine whether to overwrite
or install as .pacnew. So in this case pacman just balked at installing the
font, issued the warnings and quit.

	Now I (at least think I) understand.

-- 
David C. Rankin, J.D.,P.E.
Rankin Law Firm, PLLC
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