📝 Major notes and package defaults for gentoo

gentoo/portage.md

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+# Portage (Gentoo Package Manager)
+
+Gentoo's Package Manager is extensive. This doc is just to go over the very
+basics that are specific to my workflow/machine.
+
+## Basics
+
+Updating all packages can be done:
+
+```sh
+emaint sync &&
+emerge -avuDN @world &&
+dispatch-conf &&
+emerge -a --distclean &&
+```
+
+## Unmasking
+
+Oftentimes you might receive an error like the following:
+
+```
+These are the packages that would be merged, in order:
+
+Calculating dependencies... done!
+
+!!! All ebuilds that could satisfy "=dev-java/eclipse-ecj-4.15" have been masked.
+!!! One of the following masked packages is required to complete your request:
+- dev-java/eclipse-ecj-4.15::gentoo (masked by: package.mask)
+/var/db/repos/gentoo/profiles/package.mask:
+# Miroslav Šulc <fordfrog@gentoo.org> (2020-02-27)
+# >=dev-java/ant-eclipse-ecj-4.10 depends on masked >=virtual/{jdk,jre}-11
+# www-servers/tomcat >= 9 depends on masked dev-java/eclipse-ecj
+
+
+For more information, see the MASKED PACKAGES section in the emerge
+man page or refer to the Gentoo Handbook.
+```
+
+Quick fix of this is simply to `emerge` the package with the autounmask flags
+before installing:
+
+```sh
+touch /etc/portage/package.accept_keywords/zzz_autounmask &&
+emerge mypackage --autounmask-write --autounmask &&
+dispatch-conf &&
+# hit u in the dispatch-conf ui
+emerge -av mypackage
+```
+
+## USE Flags
+
+USE flags can get complicated, see the
+[Gentoo Wiki](https://wiki.gentoo.org/wiki/USE_flag) on the subject.
+
+## CFLAGS
+
+CFLAGS can indeed adjust compilation speed and binary size depending on
+settings. See [GCC optimization](https://wiki.gentoo.org/wiki/GCC_optimization)
+for the full details.
+
+Of interest are
+[`-march`](https://wiki.gentoo.org/wiki/GCC_optimization#-march),
+[`-O`](https://wiki.gentoo.org/wiki/GCC_optimization#-O),
+[-pipe](https://wiki.gentoo.org/wiki/GCC_optimization#-pipe)
+
+As long as you set `-O2` or `-O3`, this should be a good compromise with the
+above. Of interest, but is more dangerous/experimental to play around is
+[LTO](https://wiki.gentoo.org/wiki/LTO) and
+[PGO](https://wiki.gentoo.org/wiki/GCC_optimization#Profile_Guided_Optimization_(PGO)).
+
+## More
+
+This is just a note saying that this document is very very sparse on purpose.
+Always consult the Gentoo wiki, this document is meant more as a resource for
+myself than any sort of actual guide.