| Gentoo fundamentals | ||
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Chapter 14. Gentoo Linux |  |
| Gentoo fundamentals | ||
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Chapter 14. Gentoo Linux | |
Gentoo is (per default) always compiling the source. It supports binary packages that can make use of installing deb or rpm packages.
To allow automatic compilation and installation Gentoo uses ebuilds, that contain all necessary steps to get the packages. Ebuilds can be considered as packages, but instead of having the actual binaries and data inside, they hold the information where to retrieve the source and how to create a binary.
The program emerge is used to install packages.
emerge <ebuildname> installs packets. emerge umerge <ebuild> removes the packet.
On of the fundamental concepts of Gentoo is that the packages are not directly installed into the system. They are first installed in a temporary location and then copied (merged) file by file to the real system. This way Gentoo remembers all the files installed (merged, copied) and knows what to remove when the package gets updated or removed.
Ebuilds are in repositories. If an ebuild does not exist it is better to create an ebuild and put it in a personal overlay. Don't install it manually and run into a conflict with the Gentoo packet management.
The evolution of Gentoo caused some changes, some of them are not necessary to follow since Gentoo has some backward compatibility support. Gentoo uses rolling releases so an 10 year old installation can still be updated to the newest packages, however certain things as directories where the ebuilds are remain old. If possible tho old ways just supported by backward compatibility should be identified and avoided.
Table 14.1.
| Item | deprecated old | actual | comment |
|---|---|---|---|
| repository, place where available ebuilds are |
/usr/portage
|
/var/db/repos/gentoo
|
repository overlays are placed at /var/db/repos/and are therefore handled the same way as the standard gentoo repository |
| place where downloaded package source and binary goes | /usr/portage/distfiles | /var/cache/distfiles | it is considered that the files are cached and can always be downloaded again. |
The ebuilds can be grouped in three categories :
The system ebuilds, emerge -p @system shows them. The selected profile in /var/db/repos/gentoo/profiles defines them, but the profile uses a cascading directory and file structure, therefore it is not as easy as opening a file and look at the system ebuilds.
The ebuilds installed manually that are listed in
/var/lib/portage/world
and cat /var/lib/portage/world shows them or emerge -p @world shows them plus the system ebuilds
Ebuilds depending on the installed ebuilds and get installed automatically. To see everything installed (system, world and depending ebuilds): do equery list "*" or cd /var/db/pkg/ && ls -dl */* or emerge -pe world. The numbers of ebuild listed should be consistent otherwise something is corrupt in /var/db/pkg
To get an overview emerge --depclean --pretend.
Gentoo uses the term sets emerge --list-sets to group ebuilds. To differentiate that a set is meant the @ character has to be put in front of the set name.
Use the official handbook https://wiki.gentoo.org/wiki/Handbook:Main_Page
Download the liveGUI USB image and dd if=livegui-amd64-20250420T121009Z.iso of=/dev/sdj bs=4M status=progress conv=fsync oflag=sync to move it to a USB device.
After booting from the USB device, set the key board layout and get familiar with the liveGUI.
To be root do sudo su - in the console window.
To start the installation consider one of the following approaches:
Open the gentoo handbook and copy and paste the commands from the handbook into the root console.
Run in the root console rc-service sshd start and check for the ip address ifconfig and set a root password using passwd. Then go to the familiar PC and open a root console and type ssh <ip address of the PC to be installed>. Now most of the installation work can be done on the familiar PC including writing notes. So open the Gentoo handbook and copy the commands in the ssh console. However downloading the stage3 image using a graphical browser can obviously not be done in the ssh console window, do this on the new PC or use links the command line browser.
lsblk or fdisk -l will show the disks of the new installation. sda will be the USB device that runs the liveGUI and nvme0n1 will be the M.2 Disk that gets the Gentoo installation.
gtp and uefi have replaced the older mbr (master boot record) approach. On a modern x86_64 system, partitioning the disk for gtp and uefi can be simple using 2 partitions:
A 1GByte fat32 partition used for the efi boot process
The rest of the disk can be used as root partition using ext4 or xfs
fdisk /dev/nvme0n1 can then be used to partition the disk as written in the Gentoo handbook
A question arises is a swap partition necessary or not and how big should it be. Instead of creating a swap partition a swapfile can be created at any time and can also be deleted when desired. free -h or htop will show later how the RAM is used and if swap will help.
The Gentoo handbook describes lot of options that might confuse. Follow the concept less is more or keep it simple and don't install things that are not clear. When the system is up and running additional and missing things can be added.
This section is here to remind about the few things when working with Gentoo Linux without going into the details. The reason why it is here at the beginning, is to prevent that you make a mess in your installation. If you read this book the first time and you understand none of the commands, just skip it.
It is recommended to call emerge -pv before emerging a ebuild. The useflags that the package supports are shown: The ones enabled and the ones disabled. Check what they mean by e.g. ufed and modify them as appropriate.
For the ebuilds that depend on the ones you know or the ones that make troubles use
emerge -1 <ebuild> or emerge --oneshot <ebuild> this prevents that garbage gets
registered in /var/lib/portage/world.
emerge --noreplace <ebuild> add an already emerged ebuild to the world file.
To have a clean installation, watch out what is in
/var/lib/portage/world there should be just packages listed that got installed manually and intended. All packages should be known.
For the unknown a gui portage tool or the internet can help to find out about them. If it is still unknown why they got emerged manually wipe them off the world file (do not --unmerge them since they are probably be used as dependencies for other packages).
Failures and troubles during updating gentoo ask to retry and re-emerge such packages manually. It is highly recommended to use the --oneshot or-l option in the emerge command, so they will not be registered in the
/var/lib/portage/world file. If those
options are not used, then the world file collects all trouble packages and it gets difficult to get rid of them in the future. Cleaning means --unmerge or deleting them manually in the world file.
A lost world file can be recovered using emerge gentoolkit and run regenworld (it is a
python script that does nothing else than trying to restore data from
/var/log/emerge.log ).
To verify that the world does not contain packages that depend on other emerged packages or if your world file has a couple of hundred packages, then unmask and emerge udept and run dep -wvp. If sure that you want to clean it run dep -w. However when later on deleting a front end the back-end is no longer registered in the world file and could be wiped off when running emerge --depclean. Therefore run previously emerge --depclean --pretend. Type dep -h to get the full list of options for the powerful dep command.
Those ebuilds are defined in the profile. Since profiles are cascading there is no single file to
see those ebuilds. The list of basic ebuilds is
/var/db/repos/gentoo/profiles/base/packages. To see
the complete list type emerge -pv system.
The /var/lib/portage/world contains no system
files, it just contains what has been emerged manually.
Everything that is installed can be found in /var/db/pkg. Those
directories contain lot of information relevant during the installation and information about the
packages themselves.
The magic Gentoo command is emerge.
|
emerge |
Compiles and installs new package, use this just for packages that you have selected. |
|
emerge –1 |
Compiles and installs a package, but does not add it to
|
|
emerge “< |
Installs earlier version (>newer, =exact) |
Options with long parameter form:
|
emerge --depclean |
Remove not used packages |
|
emerge --help |
Help about emerge |
|
emerge --help config |
Help about config files |
|
emerge --info |
Shows configuration of your system libraries use flags and many more |
|
emerge --pretend --update world |
Checks what is up to do |
|
emerge --search |
Looks for packets containing name |
|
emerge --searchdesc |
Looks for packets and description containing name |
|
emerge --sync |
Updates the portage tree on the computer to see what new packages are available. Net etiquette do not more than once a day |
|
emerge --unmerge |
De-installs packets |
|
emerge --update --deep --newuse world |
When you have added new use flags and want to update all |
|
emerge --update --deep world |
Does the update including dependencies |
|
emerge --update system |
Updates just the system not the packages |
|
emerge --update world |
Does the update |
|
emerge --usepkg |
Installs prebuild packet (when available, when not build from source code) |
|
emerge --usepkgonly |
Installs prebuild packet |
Options with short parameter form:
|
emerge -e system |
To recompile all with e.g. new compiler version |
|
emerge -e world |
To recompile all with e.g. new compiler version |
|
emerge -epv |
Pretend installing a package, be verbose and show the (empty)tree to see all dependencies |
|
emerge -K |
Short form of --usepkgonly |
|
emerge -k |
Short form of --usepkg |
|
emerge -pv |
Pretend installing a package and be verbose |
|
emerge -pvt |
Pretend installing a package, be verbose and use tree formatting |
|
emerge -u world |
Short form of update |
|
emerge -u world |
Updates all packets to last version |
Usually emerge takes the newest stable package (e.g. x86 keyword). However this default behavior can be changed. There are different options.
Unfortunately the same verb mask is used for two different things and creates therefore confusion. To avoid that the term hard mask has been introduced. Packages can be hard masked by the Gentoo developers. You as system administrator can just (soft) mask them. On the other side you as system administrator can unmask hard masked packages and unmask unstable packages (packages under test). In the worst case a package is masked and unstable. To use it you must hard unmask it and (soft) unmask it.
The emerge command shows information (man emerge for a complete description) about what it is doing with the package:
N new package to be installed
U update already installed package
D Downgrade package
S Slotted package
R Reemerging with same version
f fetch restricted (e.g. due to license) but already downloaded
~ unstable package
Slotted packages are packages where different versions can be installed at the same time.
Using emerge --update world does not necessary update everything as emerge -pe world shows. Files depending on the ones listed in /var/lib/portage/world might not be updated. Such file scan manually be updated using emerge -u <ebuild> but such updates usually have no noticeable effect.
EMERGE_DEFAULT_OPTS="--jobs=<n>--load-average=<m>
can be added to adjust how many jobs in parallel and how much load is used for the compilations.
To use a unstable package that is under test instead of the stable one, use the following
command to appended a line to
/etc/portage/package.keywords
echo "<=sci-electronics/eagle-4.16_p2-r2 ~x86" >> /etc/portage/package.keywords
A package.accept_kewords file has been introduced that will replace the package.keywords file. Or even worse /etc/portage/package.keywords became a directory on new systems and is no more a file, since the /etc/portage/package.keywords got too long. To convert the file to a directory, rename the file and move it to /etc/portage/package.keywords/package.keywords.file
To enable just to the current version, it is wise to do it as show above. Therefore in the future the line gets obsolete when newer stable versions are in portage and therefore the line can be wiped out.
Alternatively to the echo command the file
/etc/portage/package.keywords can be edited:
<=x11-drivers/ati-drivers-8.26.18-r1 ~x86
An unstable package could require to unmask very many additional unstable packages. emerge can do it: emerge --autounmask-write<ebuild> and then run etc-update.
To not use a specific version that caused troubles, create the file
/etc/portage/package.mask to mask the default files add
lines as:
=sys-apps/busybox-1.00-r4 =sys-libs/glibc-2.3.5 =net-misc/unison-2.12.0
Since this way of masking packages is done by the system administrator it is called soft masking.
Masked packages are different from unstable packages. Masked packages are known to have troubles,
this is why they got masked by the Gentoo developers. Since this way of masking packages is done by the
Gentoo developers it is called hard masking. Masked packages and the reasons why they got masked can be
found in /var/db/repos/gentoo/profiles/package.mask
Note that overlays can also mask packages. Therefore look to directories as:
/usr/locale/portage/layman/
<name of overlay>/profiles/package.mask
It is therefore recommend to read those files before unmasking masked packages.
To unmask a package that got masked by the Gentoo developers edit the file
/etc/portage/package.unmask and since it is probably
unstable you need to unmask it in
/etc/portage/package.keywords as well => double
unmasking.
This is an important note, since read and setup storing elogs is a must. Unfortunately the Gentoo manuals do not enough point out this important steps. If not, then the system will get sooner or later errors and requires troubleshooting.
During emerge a lot of information appears on the screen and can obviously not be read. Some of this information is vital to the Gentoo installation.
The logs can be read inside the directory /var/log/portage/elog
Usually just the file summary.log is found in this directory, but adding the following in /etc/portage/make.conf causes individual files being created:
PORTAGE_ELOG_SYSTEM="save" PORTAGE_ELOG_CLASSES="warn info error log"
On the console, those files can be viewed directly. More user friendly is to use mc and have in on window the quick view.
For a gui emerge elogviewer or emerge elogv for text based to have a list of all them to look and delete them individually.
There are also virtual packages. Virtual packages allow the use of different implementations for the same purpose. As example there are different implementations of java. A program written in java requires java being installed but does not require a specific java implementation. The dependency to the virtual java package resolves this issue and allows to choose different java implementations.
The virtual java package depends on at least one out of the java package. emerge virtual/jdk will get the default java vm
Gentoo allows that different versions of the same packages can be installed at the same time. This is necessary when a package gets a major release with incompatibilities and other packages still depend on the older version. To those packages a slot number is assigned.
With portage 2.2 a new feature is introduced. Multiple ebuilds can be emerged with a single command: emerge -av @kde
Gui tools as kuroo show you easily what has been installed. However if the list is to big, then the command line tool equery files <packagename> in combination with grep can be used. If the package documentation speaks about some files that can not be found, then the files might be still on the computer but not installed. Go to /var/cache/distfiles and browse through the zipped package.
Portage is a list of packets (programs, ebuilds) maintained by Gentoo that can be installed and managed on your computer. The portage directory can be found in the /etc/portage.make.conf file
PORTDIR="/var/db/repos/gentoo"
There are also other directories inside that contain no ebuilds as:
distfiles holds the source code downloaded from the Internet, newer installations have it in /var/cache/distfiles
eclass holds functions often be called by the ebuilds (as a library for ebuilds)
licenses holds what the name says
metadata holds a lot of different stuff as cache, dtd, glsa, news, timestamp
packages hold binary packages
profiles hold the profiles
scripts holds what the name says
The official portage can be expanded by overlays. Overlays are collections of non-official ebuilds.
Settings can be done in /etc/make.conf .
The FEATURE variable has direct influence on how portage behaves. The following line in
/etc/make.conf
FEATURES=”noman noinfo nodoc”
prevents that documentation is installed. However saving 100MB less compared to the rest is not worth losing the documentation.
The program emerge is used to deal with the portage.
To find what is in portage the following can be done:
emerge --search<criteria>
Check out https://www.gentoo.org/
use a portage GUI front end as porthole, himerge, kuroo, ... .
As time goes by, everything can be improved, but it can also become worse. A replacement of portage with promised improvements is in preparation, lets see what the future brings.
Once the https://www.gentoo.org/ web site contained a lot to browse and search throughout portage, but it disappeared due to a security issue.
If a package is installed, Gentoo downloads the source code and compiles it. You can influence
what and how it is compiled and what is added. You might want to add or remove certain functionalities
and support for other stuff (as adding IP6 support). This is archived by the use flags. Considering
those use flags, the ebuilds add or skip certain items. Use flags are defined (enabled or considered)
in the ebuilds or eclasses
(see /var/db/repos/gentoo/eclass ).
To know what use flags are available for a package and their status
type: emerge -pv <ebuild>
To see for what a useflag (e.g. useflag ldap) is used by a package, emerge euses and type
euses ldap or use equery hasuse ldap found in gentoolkit
See: https://www.gentoo.org/support/use-flags/
There are the following kinds of use flags and places where there are defined:
Global useflags
/var/db/repos/gentoo/profiles/use.desc
Local use flags for specific packages
/var/db/repos/gentoo/profiles/use.local.desc
(This file is deprecated as per GLEP 56 in favor of metadata.xml)
Some useflag names are ambiguous since they exist as global as well as local use flag as mtp.
Expanded use flags
/var/db/repos/gentoo/profiles/base/make.defaults (See USE_EXPAND: VIDEO_CARDS, LIRC_DEVICES, LINGUAS, ...) . Regular use flags have just two conditions set or not set. The expanded use flags are a list of items.
CURL_QUIC="openssl" can also be written and is used as by emerge as curl_quic_openssl
To find use flags:
cat /var/db/repos/gentoo/profiles/use.desc |grep lirc
cat /var/db/repos/gentoo/profiles/use.local.desc |grep lirc
Useflags should just be set when necessary. As example the profile for desktop computers /var/db/repos/gentoo/profiles/targets/desktop/make.defaults hold the X useflag, so there is no need to set it again manually. emerge -pv<ebuild> shows what the default settings do. Also activating useflags that are not used does not make sense.
emerge ufed the use flag editor to change use flag settings. If no package is shown, it is a global use flag, if a package is shown it is a local useflag
Once the default where in a single file
/etc/make.profile/make.defaults but in newer versions /etc/make.profile is a link to cascading profiles as /var/db/repos/gentoo/profiles/default/linux/x86/10.0/desktop.
Useflags can be set global, so they apply for every package emerged or they can be set just for a single package.
When setting useflags globally side effects might happen as troubles with other packages. Setting them package based is therefore less problematic.
Global useflags should be set Global useflags are set in /etc/portage/make.conf
If a – is put in front then it is disabled.
Package specific use flags can be set to
/etc/portage/package.use as
media-tv/xmltv de_tvtoday
Or cleared to avoid that a certain package uses a useflag that has been globally set
dev-java/blackdown-jdk -doc
This example emerged blackdown java without the documentation that gets loaded from Sun Microsystems thats very often causes problems.
It is wise to do first an emerge -pv that means pretend verbose. Nothing happen but you see what use flags are there and if they are set or not set.
Sometime some programs rely on other programs and how they got complied (their use flag settings), this can give some problems and error messages during the emerge. To get rid, you have to find the program an recompile (reemerging) with the appropriate use flag setting. Or do a radical step by:
emerge --update --deep --newuse world
emerge --p --depclean
Then if nothing dangerous shows up do
emerge --depclean
emerge @preserved-rebuild
To see whats up with the use flags set or clear one useflag and check its impact with
emerge --update --deep --pretend world
Or to see all of them being used:
emerge -evp system
emerge -evp world
Or for a package
emerge <package> -pv
- are use flags not set
red are active use flags
blue are inactive use flag
% after the use flag shows that an update of a package has introduced this new use flag
* after the use flag shows that use flag status does not match with what has been installed.
yellow are use flags that will be added by new emerges
green are use flags that have been used previously for the package
Gentoo has the tool eselect to do tasks as selecting symlinks and other things automatic in a more safe way than doing the same manually.
It is modular where eselect help shows what is available.
eselect news list will list the news and eselect news read new will show the news.
License groups are defined in /var/db/repos/gentoo/profiles/license_groups
Licenses are controlled by the ACCEPT_LICENSE variable in /etc/portage/make.conf
ACCEPT_LICENSE="* -@EULA"
* the wild-card means all known licenses
- means minus
@ means that the following is a name of a group of licenses and not a single license
All together mean all known licenses are automatically accepted except the licenses the require a End User License Agreement
Licenses can also be accepted by per-package basis in /etc/portage/package.license
If the license is not accepted messages pop up as:
!!! All ebuilds that could satisfy "app-emulation/virtualbox-bin" have been masked. !!! One of the following masked packages is required to complete your request: - app-emulation/virtualbox-bin-3.1.2 (masked by: PUEL license(s)) A copy of the "PUEL" license is located at "/usr/portage/licenses/PUEL".
Then it is due to the lawyers out there. Especially sun Microsystems and now Oracle that owns them tries to give you a hard time. Maybe worth to use an other java implementation as Alternatives are switching to dev-java/icedtea-bin:6 or the source-based dev-java/icedtea:6?
To accept the license put something as
ACCEPT_LICENSE="${ACCEPT_LICENSE} PUEL"
into /etc/portage/make.conf.
Or add it to the license file /etc/portage/package.license
>=dev-java/sun-jdk-1.6.0.29-r1 Oracle-BCLA-JavaSE
Example 14.1. License blockage example
!!! The following updates are masked by LICENSE changes: - www-plugins/adobe-flash-11.2.202.262::gentoo (masked by: AdobeFlash-11.x license(s)) A copy of the 'AdobeFlash-11.x' license is located at '/usr/portage/licenses/AdobeFlash-11.x'. For more information, see the MASKED PACKAGES section in the emerge man page or refer to the Gentoo Handbook.
Does not give a useful hint what to do. To solve it add the following:
>=www-plugins/adobe-flash-11.2.202.262 AdobeFlash-11.x
to:
/etc/portage/package.license
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| Chapter 14. Gentoo Linux |
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