Bug: https://bugs.gentoo.org/886247 Bug: https://bugs.gentoo.org/886017 Signed-off-by: Sam James <s...@gentoo.org> --- ...022-12-24-alternatives-introduction.en.txt | 92 +++++++++++++++++++ 1 file changed, 92 insertions(+) create mode 100644 2022-12-24-alternatives-introduction/2022-12-24-alternatives-introduction.en.txt
diff --git a/2022-12-24-alternatives-introduction/2022-12-24-alternatives-introduction.en.txt b/2022-12-24-alternatives-introduction/2022-12-24-alternatives-introduction.en.txt new file mode 100644 index 0000000..841e07a --- /dev/null +++ b/2022-12-24-alternatives-introduction/2022-12-24-alternatives-introduction.en.txt @@ -0,0 +1,92 @@ +Title: Introduction of app-alternatives ebuilds +Author: Sam James <s...@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]. + +## Per-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: +1. # emerge --sync +2. # 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 /usr/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 /usr/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 -- 2.39.0