difference update, upgrade, upgrade distros

[uk2]

Hello

I am just wondering what the difference is between them.

When I want to do a update I do this:
sudo apt-get update
Does this download all the latest updates.

And then
sudo apt-get upgrade
Does this install all the updates that have been downloaded.

And this:
sudo apt-get upgrade distros
Does this update to the next available version. For example. I currently have 8.04.2. So I will upgrade to 8.04.3

Many thanks,

[Partyboi2]

Hi,
You can read more about apt by checking out the man pages which can be done by typing

man apt-get in a terminal.


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
/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.