Here in Gentoo land, the concept of upgrading is quite different compared to the rest of the Linux world. You probably already know that we never got in touch with the "classic" way of upgrading software: waiting for a new release, downloading it, burning, putting it in the cdrom drive and then following the upgrade instructions.

You know (being a Gentoo user after all) that this process is extremely frustrating for power users that want to live on the bleeding edge. Even power users from other distributions probably share the same feelings, given the popularity and spread of tools like apt or apt-rpm which make it possible to have quick and frequent updates. However, no distribution is more suited than Gentoo to satisfy these kind of demanding users. From the beginning, Gentoo was designed around the concept of fast, incremental updates.

Ideally, you install once and never bother with releases: just follow the instructions in A Portage Introduction in the Gentoo Handbook that explain how to keep your system up to date. While that's the way things usually go, sometimes changes are made to the core system which require updates to be done manually.

A recurring question about the Gentoo release process is: "Why roll out new releases frequently, if they are not intended to let users update software?" There are various reasons:

• A new release means new Installation CDs with bugfixes and more features
• A new release provides an updated set of GRP packages, so that users that choose "the fast way" to install (stage3 + precompiled packages) end up with a system that is not outdated
• Finally, a new release may, from time to time, implement some features that are incompatible with previous releases

When a release includes new incompatible features, or provides a set of core packages and settings that deeply modify the behavior of the system, we say that it provides a new profile.

A profile is a set of configuration files, stored in a subdirectory of /usr/portage/profiles, that describe things such as the ebuilds that are considered system packages, the default USE flags, the default mapping for virtual packages, and the architecture on which the system is running.

The profile in use is determined by the symbolic link /etc/make.profile, which points to a subdirectory of /usr/portage/profiles which holds the profile files. For instance, the default x86 2008.0 profile can be found at /usr/portage/profiles/default/linux/x86/2008.0. The files in the parent directories are part of the profile as well (and are therefore shared by different subprofiles). This is why we call these cascaded profiles.

Profiles obsoleted by new ones are kept in /usr/portage/profiles along with the current ones, but they are marked as deprecated. When that happens a file named deprecated is put in the profile directory. The content of this file is the name of the profile that should be "upgraded to"; Portage uses this information to automatically warn you when you should update to a new profile.

There are various reasons that a new profile may be created: the release of new versions of core packages (such as baselayout, gcc, or glibc) that are incompatible with previous versions, a change in the default USE flags or in the virtual mappings, or maybe a change in system-wide settings.

If a new Gentoo release does not include a new profile then you can safely pretend that it never happened. :)

If you update your installed packages as explained in the Gentoo Handbook, then your system will be exactly the same as one that has been installed using the new release.

If a release (such as 2008.0 for x86) introduces a new profile, you have the choice to migrate to the new profile.

Naturally, you are not forced to do so, and you can continue to use the old profile and just update your packages as explained in the Gentoo Handbook.

However, Gentoo strongly recommends updating your profile if it becomes deprecated. When this happens, it means that Gentoo developers no longer plan on supporting it.

If you decide to migrate to the new profile, then you will have to manually perform the update. The way you update may vary significantly from release to release; it depends on how deep the modifications introduced in the new profile are.

In the simplest case you only have to change the /etc/make.profile symlink, in the worst case you may have to recompile your system from scratch while doing a neat voodoo dance. Migration is usually covered in the release notes. You can also find instructions at the end of this guide.

You can view the list of profiles on your architecture officially supported by Gentoo developers when you emerge eselect and then run the following command:

# eselect profile list

First, run emerge eselect. The eselect utility will let you view and select profiles easily, without needing to create or remove symlinks by hand.

(View available profiles)
# eselect profile list

(Select the number of your desired profile from the list)
# eselect profile set <number>

If you'd still prefer to change profiles manually, then simply do the following:

# rm /etc/make.profile
# ln -s ../usr/portage/profiles/<selected profile> /etc/make.profile

If you intend to upgrade to these profiles, you should be aware that they expect the system to be set to a Unicode locale by default; specifically that UNICODE="yes" is set in /etc/rc.conf. For this to work, you must have created a Unicode locale for your system to use. Please read our UTF-8 guide to learn how to create the proper locale.

Alternatively, if you do not wish to set a locale, you should specify UNICODE="no" in /etc/rc.conf, and re-emerge baselayout (or wait until your next baselayout update) with the -unicode USE flag. You can set -unicode just for baselayout, or you can set it globally for all packages by adding it to your USE variable in /etc/make.conf.

(To remove Unicode support just for baselayout)
# echo "sys-apps/baselayout -unicode" >> /etc/portage/package.use
# emerge -a baselayout

(To remove Unicode support from your whole system)
# nano -w /etc/make.conf
USE="-unicode"
# emerge -a baselayout

Finally, follow the general instructions for updating your profile.

To switch to the 2006.0 profile, point the /etc/make.profile symlink to the new location. Make sure your Portage is updated before you change your profile.

# rm /etc/make.profile
# ln -s ../usr/portage/profiles/<selected profile> /etc/make.profile

alpha - Users that use a 2.4 kernel or don't want to use NPTL should use the default-linux/alpha/no-nptl profile. More information is available in the alpha release notes.

ppc - The merge of the ppc32 and ppc64 profiles went forward. The ppc32 profile has been changed in a way that offers a minimalistic generic profile for all purposes, located in default-linux/ppc/ppc32. The release-dependent profile is optimized for desktop-usage and located in default-linux/ppc/ppc32/2006.0. There are some subprofiles available for G3 and G4 processors, and G3/Pegasos and G4/Pegasos for the Pegasos Open Desktop Workstation. Make sure you choose the correct subprofile for your system when migrating to a 2006.0 profile.

sparc - Upgrading to the 2.4-kernel based 2006.0/2.4 profile requires manual user intervention (unmerging java stuff) and an emerge -e world because of the gcc upgrade.
Upgrading to the 2.6-kernel based 2006.0 profile which is not considered stable also requires an entry in /etc/portage/package.unmask to umask a 2.6 version of gentoo-sources and a full rebuild.

All other archs - There are no fundamental changes in this profile. No specific action needs to be performed.

To switch to the 2005.1 profile, point the /etc/make.profile symlink to the new location. Make sure your Portage is updated before you change your profile.

# rm /etc/make.profile
# ln -s ../usr/portage/profiles/<selected profile> /etc/make.profile

All archs - There are no fundamental changes in this profile. No specific action needs to be performed.

ppc - With the 2005.1 release, the ppc and ppc64 profiles were merged and a number of subprofiles for specific subarchitectures were created. Make sure you choose the correct subprofile for your system when migrating to a 2005.1 profile.

With the introduction of 2005.0, several architectures have decided to define additional profiles. Make sure you read the description of said profiles before you decide to migrate to one of them. Most architectures now also default to the 2.6 kernel tree where 2.4 was chosen previously.

Some architectures require a bit more actions to be completed in order to convert from one profile to another. If that is the case, the step-by-step guides are linked from the table.

To switch to the selected profile, point the /etc/make.profile symlink to the new location. Make sure your Portage is updated before you change your profile!

# rm /etc/make.profile
# ln -s ../usr/portage/profiles/<selected profile> /etc/make.profile

If you are running a Linux 2.4-based system but want to migrate to a 2.6-based kernel, make sure you read our Gentoo Linux 2.6 Migration Guide.

With the introduction of the 2004.3 profiles, users are not going to see huge modifications of their systems (see below for details). However, Gentoo developers decided to push out this new profile and to deprecate quite a few of the old ones to speed up the adoption of stacked profiles, that is, the profiles that follow the new layout of the /usr/portage/profiles directory, for instance /usr/portage/profiles/default-linux/x86/2004.3 (supported by Portage 2.0.51 or later).

To switch to the 2004.3 profile, point the /etc/make.profile symlink to the new location:

substitute <arch> with your arch
# rm /etc/make.profile
# ln -s ../usr/portage/profiles/default-linux/<arch>/2004.3 /etc/make.profile

All archs - As said above, there are no big changes introduced in this profile. However, it should be noted that sys-apps/slocate and net-misc/dhcpcd are no longer considered system packages. This means that if you run emerge --depclean, Portage will try to remove them from your system. If you need any of those packages, add them to /var/lib/portage/world after the profile switch, or manually emerge them.

ppc - sys-fs/udev is now the default instead of sys-fs/devfs for newly installed machines. This has no effect on already installed machines, though.

Although this section does not seem to integrate well in this upgrading guide, it is quite important. Any profile listed above this section requires a Portage version that supports cascading profiles. However, some obsoleted profiles don't allow the user to upgrade Portage or the user is using a profile that isn't available anymore - any attempt to upgrade Portage will result in a failure.

To work around this problem, users can set a temporary symbolic link to the obsolete profile, allowing them to upgrade their Portage after which they can continue with the upgrade procedure set forth in this guide. Please substitute <arch> with your respective architecture:

# rm /etc/make.profile
# cd /etc
# ln -sf ../usr/portage/profiles/obsolete/<arch> make.profile
# emerge -n '>=sys-apps/portage-2.0.51'

To switch to the 2004.2 profile, point the /etc/make.profile symlink to the new location:

substitute <arch> with your arch
# rm /etc/make.profile
# ln -s ../usr/portage/profiles/default-linux/<arch>/2004.2 /etc/make.profile

x86 - This profile changes the default X11 implementation from x11-base/xfree to x11-base/xorg-x11. This change only touches the default value, and is only relevant for those who have not installed an X server yet. If you already have one installed, then it will not affect you at all; you are free to switch from one X server to the other exactly as before.

amd64 - There are no fundamental changes from previous profiles, no specific action needs to be performed.

To switch to the 2004.0 profile, point the /etc/make.profile symlink to the new location:

substitute <arch> with your arch
# rm /etc/make.profile
# ln -s ../usr/portage/profiles/default-<arch>-2004.0 /etc/make.profile

All archs - There are no fundamental changes from previous profiles, no specific action needs to be performed.

The instructions for this upgrade are quite complex, you can find them here.