RFC: installation paths and runtime paths

[o11c]

The directories I am describing is not new; it is only a collection of existing standard practices.

Current practice

Currently, common practice is to install rust packages into ~/.rust. This is unfriendly, since you're adding a junk dir in the middle of someone else's home, and there are better places (mostly ~/.local/lib/rust, but do keep reading).

Installation variables

These are often embedded into the application at configure-time (unlike DESTDIR, which must not be, since it is only for use of packaging tools).

variable	default	purpose
PREFIX	/usr/local	architecture-independent files (/usr for distros)
EPREFIX	${PREFIX}	architecture-dependent files
BINDIR	${EPREFIX}/bin	user executables (${PREFIX}/games for games)
SBINDIR	${EPREFIX}/sbin	system admin executables
LIBEXECDIR	${EPREFIX}/libexec	program executables
SYSCONFDIR	${PREFIX}/etc	read-only single-machine data (/etc for distros)
LOCALSTATEDIR	${PREFIX}/var	modifiable single-machine data (/var for distros)
LIBDIR	${EPREFIX}/lib	object code libraries
DATAROOTDIR	${PREFIX}/share	read-only arch.-independent data root
DATADIR	${DATAROOTDIR}	read-only architecture-independent data (${PREFIX}/share/games for games) (should only use ${DATADIR}/${PACKAGE}/)
LOCALEDIR	${DATAROOTDIR}/locale	locale-dependent data
DOCDIR	${DATAROOTDIR}/doc/${PACKAGE}	documentation root

Working in ${HOME}

(XDG; this applies even if you were installed globally)

variable	default	purpose
XDG_DATA_HOME	$HOME/.local/share	dir to read/write user data
XDG_DATA_DIRS	/usr/local/share/:/usr/share/	dirs to read data after that (should include ${DATADIR} if you change that)
XDG_CONFIG_HOME	$HOME/.config	dir to read/write user config
XDG_CONFIG_DIRS	/etc/xdg	dirs to read config after that
XDG_CACHE_HOME	$HOME/.cache	dir to read/write nonessential temporary files
XDG_RUNTIME_DIR	None (supposed to be set by session manager, often unavailable)	private (0700) dir for sockets and named pipes

(To encourage the development of well-behaved software, some helper functions should be put in one of the standard libraries)

Practical installation into ${HOME}

variable	default
PREFIX	${HOME}/.local
BINDIR	${HOME}/bin
DATADIR	${XDG_DATA_HOME}
SBINDIR	hopeless
SYSCONFDIR	${XDG_CONFIG_HOME}
LOCALSTATEDIR	if an application needs this, it probably can't be installed as user. However, ${LOCALSTATEDIR}/cache is vaguely similar to ${XDG_CACHE_HOME} and ${LOCALSTATEDIR}/run is vaguely similar to ${XDG_RUNTIME_DIR}

[emberian]

This is awesome information to have. But, what is actionable that we should change right now, if anything? Does rustc need to take any of these into account, or just packaging tools?

[emberian]

(cc @thestinger)

[lucab]

@cmr this is something mostly for the new-to-come package manager. However, some parts also impact rustc (eg. LIBDIR) and should be taken into account when touching other stuff like rpaths (#11746).

[huonw]

cc @wycats @carlhuda @carllerche

[steveklabnik]

Closing, as the issue on the Cargo repo covers this.