TMPFS

NuttX TMPFS file system is a tiny dynamic RAM based file system.

It can be enabled by adding CONFIG_FS_TMPFS=y to the configuration at build time.

At runtime, simply use mount -t tmpfs /tmp to have a /tmp folder backed by TMPFS, then files and folders can be created under that folder.

Be aware that TMPFS is backed by kernel memory thus don’t expect to store big files on it and its size is limited by free kernel memory.

We can watch the size of TMPFS with df -h command, especially you can see the Size column of TMPFS changes when files are added or removed in the TMPFS folder. Changes in TMPFS size is always reflected by reverse changes of free kernel memory size.

Permissions

When CONFIG_FS_PERMISSION is enabled, tmpfs stores per-object owner, group, and mode and enforces them on path operations inside the volume. It also implements the optional mountpt_operations.permission hook.

Access into the mount from the pseudoFS is gated by the VFS (parent and mountpoint X_OK). See Filesystem Permission Interface.