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.

See also
See also the FAQ and the Portage FAQ.

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 configured package repositories and the Gentoo ebuild repository using eix:

root #eix-sync

This not only syncs the repositories, it also updates the cache used by eix to perform queries. It may be preferable to configure portage to update the cache automatically.

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

Or, for short:

root #emerge -av 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). For example:

root #emerge --ask =www-client/firefox-96.0.1
Warning
This will work temporarily, until the system is updated. During an update Portage will try to install the latest stable version of the package no matter which version is currently installed; whether the package was originally emerged via a preceding = operator or not.

To prevent Portage from automatically updating a package, add a line into a the /etc/portage/package.mask/package.mask file (create the file if it does not exist). Specify using the greater than operator (>) prefix if it is an older package than latest stable or lesser than operator (<) as a prefix if it is a newer one:

FILE /etc/portage/package.mask
<www-client/firefox-96.0.1

See /etc/portage/package.mask for more details on package masking.

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

See also
See the emerge documentation on removing packages for full information.

--deselect

Use emerge --deselect (or -W option for short) to remove the specified package from the @world set (i.e. it indicate that the package is no longer wanted):

root #emerge --deselect www-client/firefox

Now run emerge --depclean (or -c option for short). The --pretend (-p) 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:

root #emerge --ask --depclean

The --ask option is not really needed after a check via --pretend, but is included in the previous example to help avoid "copy paste" mishaps.

Tip
Do not confuse the lower case -c switch, which is short for --depclean (and is safe), with the upper case -C switch which risks damaging the system and should only be used when absolutely required (see warning in following section).

--depclean

To directly remove a package that no other packages depend on:

root #emerge --ask --verbose --depclean www-client/firefox
Calculating dependencies... done!
>>> Calculating removal order...

>>> These are the packages that would be unmerged:

 www-client/firefox
    selected: 68.5.0 
   protected: none 
     omitted: none 

All selected packages: =www-client/firefox-68.5.0

>>> 'Selected' packages are slated for removal.
>>> 'Protected' and 'omitted' packages will not be removed.

Would you like to unmerge these packages? [Yes/No]

As a safety measure, depclean will not remove any packages unless all required dependencies have been resolved. As a consequence of this, it is sometimes necessary to first run:

root #emerge --ask --verbose --update --newuse --deep @world

Use --changed-use (-U) in place of --newuse (-N) to avoid rebuilds when the only changes are USE flags added to or dropped from the repository. Use the --quiet (-q) flag for more succinct execution:

root #emerge --ask --quiet --update --changed-use --deep @world
Warning
There is an --unmerge option (-C), but this is not recommended and can break the system if not used with caution. This should only ever be used if necessary, and once properly informed of what it does. This will break the system, or other software, if used on some packages. The correct way to remove packages in Gentoo is virtually always with the --depclean option, as described above. This may sometimes be useful to temporarily remove a hard block though.

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.

See also
See upgrading Gentoo for more in depth information.

Package troubleshooting

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

root #revdep-rebuild -v

equery is part of app-portage/gentoolkit. Install 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 it gets inadvertently removed, a rescue stick/disk may be required. It may be possible to fetch glibc after setting PORTAGE_BINHOST="http://packages.gentooexperimental.org/packages/amd64-stable/" in /etc/portage/make.conf.

Rebuilds

Sometimes it's necessary to rebuild some packages for them to work properly. Here are some of the common rebuilds:

After installing a new kernel:

root #emerge @module-rebuild

After upgrading to a new version of Go:

root #emerge @golang-rebuild

For using new libraries:

root #emerge @preserved-rebuild

Portage enhancements

Manage configuration changes after an emerge completes:

root #dispatch-conf

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

Log management

genlop

genlop is a Portage log processor, also estimating build times when emerging packages.

Install app-portage/genlop by issuing:

root #emerge -a app-portage/genlop

Gather more information on 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
See Eselect/Repository for more information.

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

Restart the sshd service:

root #rc-service sshd restart

Stop the sshd service:

root #rc-service sshd stop

List services, their status, and the runlevels they belong to:

root #rc-status --all

Show enabled services and the runlevels they belong to (not whether they are running or not, just if they are enabled):

root #rc-update show

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

Tips

Search packages in Portage by regular expressions

To search packages in Portage by regular expressions:

root #emerge -s "%^python$"

Generate metadata caches

Ebuild repositories 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

External resources