How to place / store a file in memory on linux?

Question

I have read somewhere that one can put a file on a linux system into memory, and loading it will be superfast.

How do I do this? How do I verify the file is loaded from memory?

Answer 1

If your operating system is aiming for POSIX compliance, you probably already have an tmpfs filesystem that you can write to at /dev/shm.

$ >/dev/shm/foo
$ df /dev/shm/foo
Filesystem           1K-blocks      Used Available Use% Mounted on
tmpfs                   224088         0    224088   0% /dev/shm

This may use swap, however. For a true ramdisk (that won't swap), you need to use the ramfs filesystem.

mount ramfs -t ramfs /mountpoint

Answer 2

It's called a ramdisk. You can simply mount your RAM as follows:

mount tmpfs <mountpoint> -t tmpfs -o size=2G

This creates a ramdisk of 2 GiB. For more information see man mount and search for tmpfs.