Tmpfs is a file system which keeps all of its files in virtual memory.

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

tmpfs puts everything into the kernel internal caches and grows and shrinks to accommodate the files it contains and is able to swap unneeded pages out to swap space, if swap was enabled for the tmpfs mount. tmpfs also supports THP.^[1]

The tmpfs filesystem can now be mounted in a case-folding mode where file names are no longer case-sensitive. PS all new dir in FS will be created with the casefold flag, this also means that mountpoint will still be case-sensitive. ^[2]