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AMD64 Handbook
About the installation
Choosing the media
Configuring the network
Preparing the disks
The stage file
Installing base system
Configuring the kernel
Configuring the system
Installing tools
Configuring the bootloader
Working with Gentoo
Portage introduction
USE flags
Portage features
Initscript system
Environment variables
Working with Portage
Files and directories
Mixing software branches
Additional tools
Custom package repository
Advanced features
OpenRC network configuration
Getting started
Advanced configuration
Modular networking
Adding functionality
Dynamic management

Portage configuration

As noted previously, Portage is configurable through many variables which should be defined in /etc/portage/make.conf or one of the subdirectories of /etc/portage/. Please refer to the make.conf and portage man pages for more and complete information:

user $man make.conf
user $man portage

Build-specific options

Configure and compiler options

When Portage builds applications, it passes the contents of the following variables to the compiler and configure script:

Define the desired compiler flags for C and C++ compiling.
Defines the build host information for the application's configure script
Passed to the make command and is usually set to define the amount of parallelism used during the compilation. More information about the make options can be found in the make man page.

The USE variable is also used during configure and compilations but has been explained in great detail in previous chapters.

Merge options

When Portage has merged a newer version of a certain software title, it will remove the obsoleted files of the older version from the system. Portage gives the user a 5 second delay before unmerging the older version. These 5 seconds are defined by the CLEAN_DELAY variable.

It is possible to tell emerge to use certain options every time it is run by setting EMERGE_DEFAULT_OPTS. Some useful options would be --ask, --verbose, --tree, and so on.

Configuration file protection

Portage protected locations

Portage overwrites files provided by newer versions of a software title if the files aren't stored in a protected location. These protected locations are defined by the CONFIG_PROTECT variable and are generally configuration file locations. The directory listing is space-delimited.

A file that would be written in such a protected location is renamed and the user is warned about the presence of a newer version of the (presumable) configuration file.

To find out about the current CONFIG_PROTECT setting, use the emerge --info output:

user $emerge --info | grep 'CONFIG_PROTECT='

More information about Portage's configuration file protection is available in the CONFIGURATION FILES section of the emerge manpage:

user $man emerge

Excluding directories

To 'unprotect' certain subdirectories of protected locations users can use the CONFIG_PROTECT_MASK variable.

Download options

Server locations

When the requested information or data is not available on the system, Portage will retrieve it from the Internet. The server locations for the various information and data channels are defined by the following variables:

Defines a list of server locations which contain source code (distfiles).
Defines a particular server location containing prebuilt packages for the system.

A third setting involves the location of the rsync server which users use to update their local Gentoo repository. This is defined in the /etc/portage/repos.conf file (or a file inside that directory if it is defined as a directory):

Defines the type of server and defaults to rsync.
Defines a particular server which Portage uses to fetch the Gentoo repository.

The GENTOO_MIRRORS, sync-type, and sync-uri variables can be set automatically through the mirrorselect application. Of course, app-portage/mirrorselect needs to be installed first before it can be used. For more information, see mirrorselect's online help:

root #mirrorselect --help

If the environment requires the use of a proxy server, then the http_proxy, ftp_proxy, and RSYNC_PROXY variables can be declared.

Fetch commands

When Portage needs to fetch source code, it uses wget by default. This can be changed through the FETCHCOMMAND variable.

Portage is able to resume partially downloaded source code. It uses wget by default, but this can be altered through the RESUMECOMMAND variable.

Make sure that the FETCHCOMMAND and RESUMECOMMAND store the source code in the correct location. Inside the variables the \${URI} and \${DISTDIR} variables can be used to point to the source code location and distfiles location respectively.

It is also possible to define protocol-specific handlers with FETCHCOMMAND_HTTP, FETCHCOMMAND_FTP, RESUMECOMMAND_HTTP, RESUMECOMMAND_FTP, and so on.

Rsync settings

It is not possible to alter the rsync command used by Portage to update the Gentoo repository, but it is possible to set some variables related to the rsync command:

Sets a number of default variables used during sync, each space-separated. These shouldn't be changed unless you know exactly what you're doing. Note that certain absolutely required options will always be used even if PORTAGE_RSYNC_OPTS is empty.
Used to set additional options when syncing. Each option should be space separated:
This defines the number of seconds an rsync connection can idle before rsync sees the connection as timed-out. This variable defaults to 180 but dialup users or individuals with slow computers might want to set this to 300 or higher.
This points to a file listing the packages and/or categories rsync should ignore during the update process. In this case, it points to /etc/portage/rsync_excludes.
Reduces output to the screen.
Prints a complete filelist.
Displays a progress meter for each file.
Defines how many times rsync should try connecting to the mirror pointed to by the SYNC variable before bailing out. This variable defaults to 3.

For more information on these options and others, please read man rsync.

Gentoo configuration

Branch selection

It is possible to change the default branch with the ACCEPT_KEYWORDS variable. It defaults to the architecture's stable branch. More information on Gentoo's branches can be found in the next chapter.

Portage features

It is possible to activate certain portage features through the FEATURES variable. The Portage features have been discussed in previous chapters.

Portage behavior

Resource management

With the PORTAGE_NICENESS variable users can augment or reduce the nice value Portage will use while running. The PORTAGE_NICENESS value is added to the current nice value of Portage.

For more information about nice values, see Portage niceness and the nice man page:

user $man nice

Output behavior

The NOCOLOR variable, which defaults to false, defines if Portage should disable the use of colored output.