I just ran df -h a minute ago and noticed a filesystem has been added that I'm not familiar with. Does anyone know why /run exists? Is this something that's been added by the kernel? By Arch Linux?
run 10M 236K 9.8M 3% /run 
2 Answers
Apparently, many tools (among them udev) will soon require a /run/ directory that is mounted early (as tmpfs). Arch developers introduced /run last month to prepare for this.
The udev runtime data moved from
/dev/.udev/to/run/udev/. The/runmountpoint is supposed to be atmpfsmounted during early boot, available and writable to for all tools at any time during bootup, it replaces/var/run/, which should become a symlink some day.(1)
There is more detail here (now dead, link to archive).
(1) From thread on the Arch Projects ML
- 2is it only for Arch or what ?
/runwill be add in RHEL/CentOs, Ubuntu ?Rahul Patil– Rahul Patil2013-04-07 18:59:45 +00:00Commented Apr 7, 2013 at 18:59 - 3Do files get automatically deleted when the process stops running?Ian Ringrose– Ian Ringrose2016-12-08 09:49:23 +00:00Commented Dec 8, 2016 at 9:49
- 2@Ian, if it's a tmpfs filesystem, then on reboot it will be emptied. Your question: as I know, files would not be automatically deleted, rather process itself has to do proper cleanup.anon– anon2017-02-05 05:49:55 +00:00Commented Feb 5, 2017 at 5:49
- @BulatM. tmpfs is explicitly RAM-backed (it will swap though if not all fits in RAM), so on power off everything in /run is lost by design, and no process has to go and clean up previous files.joonas.fi– joonas.fi2021-09-12 09:15:09 +00:00Commented Sep 12, 2021 at 9:15
The /run directory is the companion directory to /var/run. Like for example /bin is the companion of /usr/bin.
That means that daemons like systemd and udev, which are started very early in the boot process - and perhaps before /var/run is available (i.e. mounted) - have with /run a standardized file system location available where they can store runtime information.
Like /bin contains important programs, which may be needed in the boot process before /usr is available (in case it is on its own filesystem).
The /run idea is a relatively new idea/standard.
- 3Arch's
/var/rundirectory is symlinked to/run.user26112– user261122013-04-20 22:24:20 +00:00Commented Apr 20, 2013 at 22:24 - 3Debian's
/var/runis also symlinked to/runnaoko– naoko2016-01-16 14:04:12 +00:00Commented Jan 16, 2016 at 14:04 - 2So is Ubuntu 16.10's.Federico Poloni– Federico Poloni2017-03-27 18:01:17 +00:00Commented Mar 27, 2017 at 18:01
- 12This answer is misleading. /run exists because /var/run was the wrong location, and most distros either symlink or bind mount them to each other. They are not intended to be separate directories; /run is the correct location, /var/run is kept around to support legacy software. See lwn.net/Articles/436012 for the motivation behind it.Matthew Sharp– Matthew Sharp2020-12-24 04:48:51 +00:00Commented Dec 24, 2020 at 4:48
- 2@maxschlepzig Yes I did. My comment was probably a bit non-specific, but it would help if you were more specific about what is misleading in my comment.Matthew Sharp– Matthew Sharp2020-12-26 19:25:38 +00:00Commented Dec 26, 2020 at 19:25
/runrelease goal document, which includes details about how the change applies to 7.0+. wiki.debian.org/ReleaseGoals/RunDirectory