You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
96 lines
3.8 KiB
96 lines
3.8 KiB
2 years ago
|
Title: Introduction of app-alternatives ebuilds
|
||
|
Author: Sam James <sam@gentoo.org>
|
||
|
Posted: 2022-12-24
|
||
|
Revision: 1
|
||
|
News-Item-Format: 2.0
|
||
|
|
||
|
Gentoo is introducing a new category of ebuilds called 'app-alternatives'
|
||
|
to handle cases where a symlink for a common binary may want to be switched
|
||
|
between different packages by a user.
|
||
|
|
||
|
Traditionally, eselect was used for this, and while eselect still has its
|
||
|
place, it's unsuitable for cases like /bin/awk and /bin/sh because it
|
||
|
prevents immutable system directories and (more importantly
|
||
|
from a package management perspective) relies on orphaned symlinks which
|
||
|
means no package owns /bin/awk, /bin/sh, etc. This is not reliable and
|
||
|
can lead to dead symlinks (or no symlink at all) in some edge cases [0].
|
||
|
|
||
|
Systems will be more robust and desired system configuration
|
||
|
can be achieved using the package manager rather than manual steps outside of it.
|
||
|
|
||
|
The initial list of packages which support alternatives is as follows:
|
||
|
- app-alternatives/awk
|
||
|
- app-alternatives/bzip2
|
||
|
- app-alternatives/bc
|
||
|
- app-alternatives/cpio
|
||
|
- app-alternatives/gzip
|
||
|
- app-alternatives/lex
|
||
|
- app-alternatives/sh
|
||
|
- app-alternatives/tar
|
||
|
- app-alternatives/yacc
|
||
|
|
||
|
The stabilization of these new ebuilds and packages depending
|
||
|
on them is ongoing in bug 886017 [1].
|
||
|
|
||
|
## Pre-upgrade requirements
|
||
|
|
||
|
The default configuration on Gentoo systems is FEATURES="protect-owned"
|
||
|
which works similarly to FEATURES="collision-protect" but it allows
|
||
|
collisions between orphaned files. In this case, a one-off collision
|
||
|
occurs as the app-alternatives/ ebuilds begin to claim once-orphaned
|
||
|
symlinks.
|
||
|
|
||
|
A similar issue occurred during the libxcrypt migration where users
|
||
|
had upgrades interrupted by using the older, more aggressive
|
||
|
FEATURES="collision-protect".
|
||
|
|
||
|
It is recommended that users alter their configuration to
|
||
|
remove references to 'collision-protect' in FEATURES and instead either
|
||
|
explicitly enable 'protect-owned' in FEATURES or rely on the default
|
||
|
(equivalent). It is also acceptable to simply disable collision-protect
|
||
|
temporarily for the purposes of this news item.
|
||
|
|
||
|
WARNING: Users with collision-protect enabled must disable FEATURES="collision-protect"
|
||
|
in /etc/portage/make.conf by removing it or setting FEATURES="-collision-protect"
|
||
|
if they have enabled it. collision-protect detects collisions between files including
|
||
|
orphaned files where no package owns the file.
|
||
|
|
||
|
## Migrating
|
||
|
|
||
|
To migrate your system, a standard world upgrade will suffice after
|
||
|
deselecting eselect-awk and eselect-sh:
|
||
|
1. # emerge --deselect app-eselect/eselect-awk app-eselect/eselect-sh
|
||
|
2. # emerge --depclean app-eselect/eselect-awk app-eselect/eselect-sh
|
||
|
3. # emerge --sync
|
||
|
4. # emerge -a -uvDU @world (or other similar standard world upgrade command)
|
||
|
|
||
|
## Configuration
|
||
|
|
||
|
Users who are not interested in using different implementations for
|
||
|
various tools listed above can ignore this section.
|
||
|
|
||
|
No configuration should be required by default, but users may wish
|
||
|
to configure the new app-alternatives/ ebuilds to their tastes as they
|
||
|
used to do via e.g. eselect-sh and eselect-awk.
|
||
|
|
||
|
Going forward, /etc/portage/package.use will be used for this purpose.
|
||
|
|
||
|
Users should review the USE flags available for the various app-alternatives
|
||
|
ebuilds like app-alternatives/sh and adjust their configuration as desired.
|
||
|
|
||
|
For example, to have /bin/gzip be provided by app-arch/pigz for automatic
|
||
|
parallelization of 'gzip', one would have the following in /etc/portage/package.use:
|
||
|
```
|
||
|
# https://wiki.gentoo.org/wiki/Gzip#Parallelization
|
||
|
# Make /bin/gzip be a symlink to pigz for a speedup in compression
|
||
|
app-alternatives/gzip -reference pigz
|
||
|
```
|
||
|
|
||
|
## Further reading
|
||
|
|
||
|
For more details, please see the technical documentation on the wiki [2].
|
||
|
|
||
|
[0] https://wiki.gentoo.org/wiki/Project:Base/Alternatives#Why.3F
|
||
|
[1] https://bugs.gentoo.org/886017
|
||
|
[2] https://wiki.gentoo.org/wiki/Project:Base/Alternatives
|