Overview
########

High level upgrade process
--------------------------

In broad terms, there are 3 steps involved in upgrading to Bazaar 2.x:

1. Upgrade the core software

2. Upgrade required plugins

3. Migrate data to the new default format.

Bazaar 2.x supports branches in earlier formats so the third step is
strictly not required. However, the new default format in Bazaar 2.x
is more space efficient, faster on large projects and provides a range
of new features, so it is recommended that most projects migrate to it
at a convenient time.

For most users, upgrading to 2.x and migrating to the new format is
straight forward. For projects with a large community of developers
though, things become more complex. In these cases, careful planning
and good communications become essential. This document provides
general advice which aims to assist in this regard. If in doubt,
please contact us on our mailing list or IRC channel with any
questions or concerns you have.


Upgrading the core software
---------------------------

The steps required to upgrade the core software vary from operating
system to operating system. There is nothing special about upgrading
from Bazaar 1.x to Bazaar 2.0 compared to upgrading from Bazaar 1.x
to Bazaar 1.y. In either case, a brief outline of the steps is given
below.

To upgrade Bazaar on Linux:

1. Ensure your package manager is configured with the required
   software sources, e.g. the official release PPA for Ubuntu:
   https://launchpad.net/~bzr/+archive

2. Use your package manager to upgrade to the latest version.

To upgrade Bazaar on Windows:

1. Uninstall the existing version using Add/Remove Programs.

2. Install the new version using the relevant installer.

To upgrade Bazaar on OS X (via the installer):

1. Install the new version using the relevant installer.

To upgrade Bazaar on OS X (via MacPorts):

1. Refresh the package metadata using **sudo port selfupdate**

2. Upgrade to the latest version using **sudo port upgrade bzr**

For further information on installing and upgrading, see
http://bazaar-vcs.org/Download.


Upgrading required plugins
--------------------------

Many plugins are not dependent on a particular Bazaar version so
upgrading them is optional. Other plugins, notably bzrtools and
bzr-svn, are more tightly associated with Bazaar's APIs so these
typically need to be upgraded in lockstep with the core software.

For Windows and OS X users, bzrtools and bzr-svn are typically
included in the installer so no special steps are required to upgrade
these. For Linux and UNIX users, bztrools, bzr-svn and many other
popular plugins can be installed and upgraded using your
platform's package manager, e.g. Synaptic on Ubuntu.


Migrating data to the new default format
----------------------------------------

As mentioned earlier, the complexity of migrating to a new format
depends on several factors, particularly project community size.
It also depends on how data is currently stored, e.g. in a
standalone branch, multiple branches in a shared repository,
stacked branches on Launchpad, etc. These various scenarios are
covered in the next chapter.