Gentoo: Using Portage
Introduction
The Gentoo Portage system is an excellent resource (in terms of software) when used correctly. However, incorrect use can lead to a bloated system with unidentifiable packages and files that cannot be updated. This guide will help users properly manage Gentoo portages to have a better system.
Installing packages
First, what do we mean by "Emerge"? The description of the emerge command (available in English here), indicates that emerge is the command-line program that serves as the interface to the Portage system. This command allows packages to be installed on the system. This installation includes (these steps are fully automated):
- finding dependencies for the package in question
- installing and/or updating dependencies if necessary
- installing the package in question
After "emerging" a package, the package is integrated into the system, which can use it directly.
The Portage tree
Portage has a large database of packages it can install. This database is called the Portage tree. This tree is stored on the hard drive, usually in the /usr/portage/ directory. To benefit from the latest packages, it is necessary to keep the tree up-to-date by synchronizing it with the official Gentoo tree, which is updated hundreds of times per day and stored on dedicated servers. This operation is done very simply on a Gentoo system connected to the Internet by typing:
It is unnecessary and not recommended to update the Portage tree more than once a day.
Choosing the right mirrors
To update its tree or obtain the sources of packages to install, Portage must download files from one of its servers. There are many mirrors containing these files, so it's better to choose one that is fastest for your geographic area. This choice can be made automatically using the mirrorselect program.
To install mirrorselect:
Once the installation is complete, to choose the 4 best mirrors for downloading sources:
You can optionally specify the -D option for a more accurate evaluation of mirror performance, but the operation will take longer. The /etc/make.conf file is automatically updated to take into account the chosen mirrors.
By running mirrorselect -ir, you can also choose the geographic area of servers to contact to synchronize the Portage tree. However, French mirrors are often not very performant, so it's best to leave the default option (SYNC="rsync://rsync.gentoo.org/gentoo-portage" in the /etc/make.conf file).
ACCEPT_KEYWORDS
The "emerge" function makes it very easy to manage the installation of stable and unstable packages (newer versions of the same software but insufficiently tested). A simple (even simplistic) method to install an unstable package (let's take vlc as an example) for an x86 architecture would be:
Unfortunately, this simple method only allows installing the unstable package (vlc) temporarily. During the next system update, the emerge -u world command will try to replace the unstable version of the package with its stable version. A cleaner method is to indicate in the /etc/portage/package.keywords file that we want to use the unstable version:
Thus, each time we want to emerge vlc (during an update for example), the ACCEPT_KEYWORDS="~x86" command will be implied.
Masked packages
Various situations may lead us to mask (or unmask) certain packages. Similarly to above, you need to use the /etc/portage/package.mask file to do this.
And to unmask a masked package, you obviously do:
USE variable
The best way to affect compilation options for packages that interest us is to assign each package (as they are installed) a line in the /etc/portage/package.use file as follows:
Package maintenance
When you want to update your system with the 'emerge -u world' command, it is possible that Portage might suggest replacing an application with an older version.
About the 'world' file
First, a brief explanation of what the 'world' file is. The 'world' file lists all packages that the user wants to be able to automatically update with Portage (using the emerge -u world command). For example, by running:
Portage records the corresponding package (here gnome-base/gnome) in the 'world' file - only gnome, not its dependencies. This is why, when you run emerge -u world, only packages in the world file are updated, not the dependencies. To update dependencies as well, use the --deep option, or -D for short.
If you lose your 'world' file, Portage will no longer know which packages you want to update, which is generally considered problematic.
To try to recover your 'world' file, run:
The world file resides in /var/lib/portage/world. You can check its content but don't edit it manually, otherwise Portage could behave erratically.
Also take a look at this thread which gives instructions for recovering your 'world' file if regenworld doesn't work.
Updating installed software
Using this method, you'll ensure that the 'emerge -u world' command does its job correctly, and you'll have a perfectly configured machine.
This is the best way to update your Gentoo system. -u for upgrade (update to the latest packages) -D for deep (update dependencies) -a for ask (displays the list of packages to update and asks before compiling) -v for verbose (displays maximum information, e.g., USE flags used for each package) -t for tree (displays packages as a dependency tree).
I recommend trying ecatmur's Cruft script or hepta_sean's more recent 'findcruft' script to keep your system clean and tidy!