Tmpfs virtual memory file system support (former shm fs)

configname: CONFIG_TMPFS

Linux Kernel Configuration
└─>File systems
└─>Pseudo filesystems
└─>Tmpfs virtual memory file system support (former shm fs)
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
Tmpfs is a file system which keeps all files in virtual memory.

Everything in tmpfs is temporary in the sense that no files will be
created on your hard drive. The files live in memory and swap
space. If you unmount a tmpfs instance, everything stored therein is
lost.

See Documentation/filesystems/tmpfs.txt for details.

depends
CONFIG_SHMEM

is selected by
CONFIG_BIG_KEYS