Sunday, August 28, 2011

How to make RAM disk in Linux

UPDATE (2014-08-27): Exactly three years later I discovered that Linux already comes with RAM disk enabled by default, mounted as `/dev/shm` (which points to `/run/shm` on Debian/Ubuntu):
$ df -h /dev/shm
Filesystem      Size  Used Avail Use% Mounted on
tmpfs            75M  4.0K   75M   1% /run/shm
See detailed info here.

*RAM disk* is a term from the past when DOS was alive and information was stored on disks instead of internet. If you created image of some disk, it was possible to load it into memory. Memory disks were useful to load software from Live CDs. Usually software needs some space to write data during boot sequence, and RAM is the fastest way to setup one.

Filesystem space in memory can be extremely useful today too. For example, to run tests without reducing resource of SSD. While the idea is not new, there was no incentive to explore it until I've run upon tmpfs reference in Ubuntu Wiki.

For example, to get 2Gb of space for files in RAM, edit /etc/fstab to add the following line:
tmpfs     /var/ramspace       tmpfs     defaults,size=2048M     0     0
/var/ramspace is now the place to store your files in memory.

No comments:

Post a Comment