December 2

Linux: Gentoo Cheat Sheet 2

Gentoo Cheat Sheet
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This is a reference card of useful commands and tips for administrating Gentoo systems. Newcomers and grey beards alike are encouraged to add their helpful tips below.


Contents
Package management
Sync methods
 Important
It is important to read and follow any and all news items that may be listed after performing a repository sync. See detailed instructions about upgrades.
Portage
Sync all repositories that are set to auto-sync including the Gentoo ebuild repository:

root #emaint --auto sync
Or, for short:

root #emaint -a sync
Sync the Gentoo ebuild repository using the mirrors by obtaining a snapshot that is (at most) a day old:

root #emerge-webrsync
emerge --sync now runs the emaint sync module with the --auto option. See Portage's sync operation.

eix
Sync custom package repository and the Gentoo ebuild repository using eix:

root #eix-sync
app-portage/eix can be installed by issuing:

root #emerge -a app-portage/eix
Gather more information on eix by reading its manual:

user $man eix
layman
 Warning
Eselect/Repository supersedes layman
If there are overlays created by layman, to sync those overlays (layman does not manage overlays defined in /etc/portage/repos.conf):

root #layman -S
app-portage/layman can be installed by issuing:

root #emerge -a app-portage/layman
Package listings
qlist
List installed packages with version number and name of overlay used:

root #qlist -IRv
qlist is provided by app-portage/portage-utils.

eix
To view the list of packages in the world set, along with their available versions, it is possible to use eix:

root #eix --world | less
To keep color in the output, use the --color switch:

root #eix --color -c --world | less -R
Package installation
In the following examples the www-client/firefox package will be used, but users should replace it with the package they want to install.

List what packages would be installed, without installing them:

user $emerge --pretend --verbose www-client/firefox
Or, for short:

user $emerge -pv www-client/firefox
List what packages would be installed, ask for confirmation before installing them:

root #emerge --ask --verbose www-client/firefox
Install a specific version
Install a specific version of a package (use "\=" (backslash and equal sign) for shells that attach special meaning to the "=" character). This example will install the package immediately, without asking for confirmation; use with caution or add the --ask option:

root #emerge =www-client/firefox-24.8.0
Install without adding to the world file
Install a package without adding it to the world file:

root #emerge --ask --oneshot www-client/firefox
Or, for short:

root #emerge -a1 www-client/firefox
Package removal
Recommended method
The recommended way to remove a package is by using emerge --deselect. This removes the specified package from the @world set (i.e. says the package is no longer wanted). To clean up the system afterwards, run depclean as given below.

root #emerge --deselect www-client/firefox
Now run emerge --depclean. The --pretend option will have emerge display what actions would be taken, this must be reviewed to make sure no required packages would be removed:

user $emerge --pretend --depclean
If emerge --depclean has not been run in a while, it may try to remove many packages - caution is advised. Once it has been assured that emerge depclean will only remove unneeded packages, run (--ask option is not needed after a check via --pretend, but is included here to help avoid "copy paste" mishaps):

root #emerge --ask --depclean
Separately, to remove a package that no other packages depend on:

root #emerge --ask --verbose --depclean www-client/firefox
As a safety measure, depclean will not remove any packages unless all required dependencies have been resolved. As a consequence of this, it often becomes necessary to run:

root #emerge --ask --verbose --update --newuse --deep @world
Use --changed-use in place of --newuse to avoid rebuilds when the only changes are USE flags added to or dropped from the repository. Use the --quiet flag for more succinct execution:

root #emerge --ask --quiet --update --changed-use --deep @world
Unclean removal (ignoring dependencies)
 Warning
Use the --unmerge, or the shorthand equivalent -C, options with extreme caution, and only if necessary, and once properly informed of what this does. This will break the system, or other software, if used on some packages. The correct way to remove packages in Gentoo is usually with the --depclean option, as described above.
Remove a package even if it is required by other packages, or is a vital system package:

root #emerge --unmerge www-client/firefox
This may sometimes be useful to temporarily remove a hard block.

The -C switch is short for --unmerge.

 Tip
Do not confuse the lower case -c switch, which is short for --depclean (and is safe), with the upper case -C switch witch risks damaging the system and should only be used when absolutely required.
Package upgrades
Upgrade all packages in the world set, their dependencies (--deep), and packages that have USE flag changes (avoiding unnecessary rebuilds when USE changes have no impact):

root #emerge --ask --verbose --update --deep --changed-use @world
The --newuse may be used in place of--changed-use to make sure that all package use flags reflect the current state of those in the Gentoo repository, though this will entail more rebuilds. The --with-bdeps=y can be used to update build time dependencies also.

Package troubleshooting
Check for and rebuild missing libraries (not normally needed):

root #revdep-rebuild -v
equery is part of app-portage/gentoolkit. You can obtain it by issuing this command:

root #emerge -a gentoolkit
Tell which installed package provides a command using equery:

user $equery b `which vim`
 Tip
qfile can provide a faster alternative to equery, if needed.
Tell which (not) installed package provides a command using e-file:

user $e-file vim
Install e-file with:

root #emerge -a app-portage/pfl
Tell which packages depend on a specific package (cat/pkg in the example) using equery:

user $equery d www-client/firefox
Get information about a package using eix:

root #eix www-client/firefox
 Warning
Do not unemerge sys-libs/glibc. It is needed by nearly every other package. If you inadvertedly remove it you may need a rescue stick/disk. You can fetch glibc after setting PORTAGE_BINHOST="http://packages.gentooexperimental.org/packages/amd64-stable/" in /etc/portage/make.conf.
Portage enhancements
Manage configuration changes after an emerge completes:

root #dispatch-conf
Or alternatively:

root #etc-update
After installations or updates
After updating perl-core packages:

root #perl-cleaner --all
or if previous didn't help:

root #perl-cleaner --reallyall -- -av
For haskell packages:

root #haskell-updater
USE flags
Obtain descriptions and usage of the USE flag X using euse:

user $euse -i X
Gather more information on euse by reading its manual page:

user $man euse
Show what packages have the mysql USE flag:

user $equery hasuse mysql
Show what packages are currently built with the mysql USE flag:

user $eix --installed-with-use mysql
Show what USE flags are available for a specific package:

user $equery uses <package-name>
Quickly add a required USE flag for a package install:

root #echo 'dev-util/cmake -qt5' >> /etc/portage/package.use
Important Portage files
/etc/portage - primary configuration directory for Portage.
/etc/portage/make.conf - Global settings (USE flags, compiler options).
/etc/portage/package.use - USE flags of individual packages. Can also be a folder containing multiple files.
/etc/portage/package.accept_keywords - Keyword individual packages; e.g. ~amd64, ~x86, or ∼arm.
/etc/portage/package.license - Accepted licenses
/var/lib/portage/world - List of explicitly installed package atoms.
/var/db/pkg - Contains information for every installed package a set of files about the installation.
Log management
genlop
genlop is a Portage log processor, also estimating build times when emerging packages.

Install genlop by issuing:

root #emerge -a app-portage/genlop
You can gather more information on app-portage/genlop by reading its manual page:

root #man genlop
View the last 10 emerges (installs):

root #genlop -l | tail -n 10
View how long emerging LibreOffice took:

root #genlop -t libreoffice
Estimate how long emerge -uND --with-bdeps=y @world will take:

root #emerge -pU @world | genlop --pretend
Watch the latest merging ebuild during system upgrades:

root #watch genlop -unc
Overlays
eselect repository
app-eselect/eselect-repository can be installed by issuing:

root #emerge -a app-eselect/eselect-repository
List all existing overlays:

user $eselect repository list
List all installed overlays:

user $eselect repository list -i
See also Eselect/Repository

Layman
 Warning
Eselect/Repository supersedes layman
app-portage/layman can be installed by issuing:

root #emerge -a app-portage/layman
List all existing overlays:

user $layman -L
List all installed overlays (layman does not manage overlays defined in /etc/portage/repos.conf):

user $layman -l
See also Layman

Services
Obtain root shell (if the current user is listed in the sudoers list):

user $sudo -i
OpenRC
Start the ssh daemon in the default runlevel at boot:

root #rc-update add sshd default
Start the sshd service now:

root #rc-service sshd start
Check if the sshd service is running:

root #rc-service sshd status
systemd
Start the ssh daemon at boot:

root #systemctl enable sshd
Start the sshd service now:

root #systemctl start sshd
Check if the sshd service is running:

root #systemctl status sshd
Gentoo Monthly Newsletter (GMN)
Search packages in Portage by regular expressions:

root #emerge -s "%^python$"
Overlays vary from very small to very large in size. As a result they slow down the majority of Portage operations. That happens because overlays do not contain metadata caches. The cache is used to speed up searches and the building of dependency trees. A neat trick is to generate local metadata cache after syncing overlays.

root #emerge --regen
This trick also works in conjunction with eix. eix-update can use metadata cache generated by emerge --regen to speed up things. To enable this, add the following variable to /etc/eixrc/00-eixrc:

FILE /etc/eixrc/00-eixrc
OVERLAY_CACHE_METHOD="assign"
qcheck
Use qcheck to verify installed packages:

root #qcheck vim-core
qcheck comes with app-portage/portage-utils and can be installed by running this command:

root #emerge -a app-portage/portage-utils
Learn more about qcheck by reading its manual page:

user $man qcheck


Copyright 2021. All rights reserved.

Posted December 2, 2021 by Timothy Conrad in category "Linux

About the Author

If I were to describe myself with one word it would be, creative. I am interested in almost everything which keeps me rather busy. Here you will find some of my technical musings. PGP: 4CB8 91EB 0C0A A530 3BE9 6D76 B076 96F1 6135 0A1B