On Ubuntu 13.04 /dev/shm is symlink to /run/shm and /run/shm is just subdirectory of /run. /run is some tmpfs which is mounted but ………… I can't find by what and how (surely it is not present in /etc/fstab and I can't grep anything sensible in /etc/init*).
While usually this directory need no attention, both while trying to setup Oracle, and while trying to setup DB2, I faced errors which in the end turned out to mean „/dev/shm is too small”. Net is full of advice how to mount --rebind run to make it bigger, but this operation nicely breaks apps which use /run and are already running at the moment rebind happens (and there are a lot of them, especially on desktop, including things like upstart, networkmanager, or udev).
My questions:
Where exactly is the code which mounts /run, when does it happen?
What should I change to increase /run size at the moment it is created? (on my laptop it takes 10% of memory - 600MB on 6GB laptop - I'd like to give it 1GB)
If 2 is impossible, what is the proper moment to rebind /run to resize it - so it happens before anythning starts actually using /run?
Does there exist any documentation on the subject? While there are many posts and notes about /run as such, I couldn't find anything about configuring it.
1 Answer
In Ubuntu those mounts are configured in /lib/init/fstab, and as it says there in the default comments, to override the settings you can simply copy the line to /etc/fstab and modify as you see fit.
# /lib/init/fstab: static file system information. # # These are the filesystems that are always mounted on boot, you can # override any of these by copying the appropriate line from this file into # /etc/fstab and tweaking it as you see fit. See fstab(5). 
