What does the following apt-get response mean?

[Jordon Bedwell]

On Dec 1, 2010, at 2:00 AM, John Conover wrote:

> Dotan Cohen writes:
>> On Wed, Dec 1, 2010 at 09:14, John Conover <conover at rahul.net> wrote:
>>> 
>>> What does the following apt-get response mean?
>>> 
>>>    root at mymachine:/ 520# apt-get upgrade
>>>    Reading package lists... Done
>>>    Building dependency tree
>>>    Reading state information... Done
>>>    The following packages have been kept back:
>>>      linux-generic linux-headers-generic linux-image-generic
>>>    0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
>>> 
>>> Why won't it upgrade it?
>>> 
>> 
>> Try using dist-upgrade instead.
>> 
> 
> Thanks, Dotan. That worked. What caused it to not upgrade?
> 
> I have three machines that are all identical, but one would not
> upgrade. Do you know what caused it?
> 
> Should "dist-upgrade" be used, always, instead of just "upgrade"?

Nothing to do with you or Ubuntu really.  It's more of a need be.  Most system administrators don't like to do major release upgrades without testing.  So dist-upgrade does things like point-releases, major releases and kernels whereas upgrade does normal and normal system software.   When you see that simply run dist-upgrade and upgrade your system, otherwise a normal upgrade is fine because there are no major system updates.