What Happens During a Distro Upgrade?

[badowskiryan]

I can't seem to find a complete answer to that question.

14.04 is about to release. I've upgraded many times before (since Edgy Eft, lol) and I know a lot of stuff happens when I do. But I don't know what, exactly.

I mean, updates happen almost daily -- packages, and occasionally the kernel. And a Linux distro is essentially a kernel with packages, right?

So what happens during a distro upgrade?

[dbass81]

I can't seem to find a complete answer to that question.

14.04 is about to release. I've upgraded many times before (since Edgy Eft, lol) and I know a lot of stuff happens when I do. But I don't know what, exactly.

I mean, updates happen almost daily -- packages, and occasionally the kernel. And a Linux distro is essentially a kernel with packages, right?

So what happens during a distro upgrade?

Taken from man apt-get:

update
update is used to resynchronize the package index files from their
sources. The indexes of available packages are fetched from the
location(s) specified in /etc/apt/sources.list. For example, when
using a Debian archive, this command retrieves and scans the
Packages.gz files, so that information about new and updated
packages is available. An update should always be performed before
an upgrade or dist-upgrade. Please be aware that the overall
progress meter will be incorrect as the size of the package files
cannot be known in advance.


upgrade
upgrade is used to install the newest versions of all packages
currently installed on the system from the sources enumerated in
/etc/apt/sources.list. Packages currently installed with new
versions available are retrieved and upgraded; under no
circumstances are currently installed packages removed, or packages
not already installed retrieved and installed. New versions of
currently installed packages that cannot be upgraded without
changing the install status of another package will be left at
their current version. An update must be performed first so that
apt-get knows that new versions of packages are available.


dist-upgrade
dist-upgrade in addition to performing the function of upgrade,
also intelligently handles changing dependencies with new versions
of packages; apt-get has a "smart" conflict resolution system, and
it will attempt to upgrade the most important packages at the
expense of less important ones if necessary. The dist-upgrade
command may therefore remove some packages. The
/etc/apt/sources.list file contains a list of locations from which
to retrieve desired package files. See also apt_preferences(5) for
a mechanism for overriding the general settings for individual
packages.

[lykwydchykyn]

I'm guessing you mean a release-upgrade, rather than a "dist-upgrade" which is a specific APT command.

Essentially, a release-upgrade works like this:
- Change sources to the new release
- Dist-upgrade
- Cleanup & reboot

And on some distros (like Debian), this is pretty much what you do to upgrade to the new release.

On Ubuntu, you don't want to do that manually. The release-upgrade tool does a lot more stuff, like safety checks (making sure you have enough disk space, the repos are available, etc), disabling bad PPAs, and handling those corner-cases that APT alone can't deal with.

If you want to see a little more verbose version of a release upgrade, you can always do it at a terminal with the command-line tool "do-release-upgrade".