apt-get holds back updates

[Derek Broughton]

Olaf Stein wrote:

> Hi List
>  
> I have a weird issue, but maybe there is is an explanation
>  
> when updating my system with
>> apt-get update
>> apt-get upgrade
>  
> the pakets
> linux-image-386 linux-restricted-modules-386
> are kept back. All others are installed/upgraded though.
>  
> Why is that and how can I have them installed??

They are "kept back" because that's what "upgrade" does.  Upgrade is the
"safe" (well, perhaps not always [1]...) upgrade path.  It will not remove
packages, and it will not install packages that don't already exist. 
Therefore it won't upgrade any packages that depend on one of those
actions.  It will only upgrade packages that already exist on the system.
("aptitude" behaves slightly different from apt-get - its "unused dependency
removal" logic is executed regardless, so packages might still be removed
in an "upgrade")

"dist-upgrade", otoh, says "go ahead, remove anything you have to and
install any new dependencies to get all these updated packages installed". 
Generally, on the stable distribution (currently breezy) this should always
be safe.  On the testing distribution (currently dapper) that may sometimes
result in an attempt to remove all of KDE or Gnome!

For safety, whenever there's a large number of updates, it's good to use
"upgrade" first, then do "dist-upgrade".  It lowers the number of decision
points for apt to try to calculate what has to be removed and added.

[1] twice in the past two weeks I've had upgrade situations where libc6 and
libc6-i686 have been upgraded and b0rked the system.  "upgrade" is not
_always_ safe, particularly when libc6 is involved.
-- 
derek