Quote:
Originally Posted by geekmaster
In the kindles (and many other linux boxes) /tmp/ is usually RAMdisk, so it would not affect the size of the user store (USB drive).
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The above is probably either a typo or an intentional simplification.
But since there is a currently open problem that is related to this....
Linux does support (if optioned at build time) RAMdisk devices.
These are an area of always resident memory which may be used as any other storage media device, including having a file system put on them. Using these reduces the physical memory page pool.
In addition, there are two memory based file systems user accessible, plus many other "nodev" filesystems.
There is a ramFS which is implemented in the VFS cache buffers without any backing store, hence are always resident. The amount of VFS cache that can be used by this system is a very limited (small) percentage of the cache buffers.
The third is the tmpFS file system, also implemented in the VFS cache buffers. In the case of this file system, it has a backing store, swap. For POSIX compliance, this file system is also accessible on the device /dev/shm.
This file system is system limited in total size to the smaller of 1/2 of memory or 1/2 of (the optional) swap. The size of each instance may also be limited by mount time option.
The directory sub-trees headed by /tmp and /var/tmp are normally mounted on a tmpFS instance.
The directory sub-tree of /run in the newer FHS layout is also normally mounted on a tmpFS instance.
The above distinctions apply in the thread about running a chroot'd system.
A user may display the contents of /proc/filesystems (cat /proc/filesystems) and make note of all the "nodev" entries.
That list varies based on build-time options and what run-time modules are currently loaded but shows that the descriptions in this thread are far from exhaustive.
Note 1: /proc (and /sys) are virtual file systems, those are implemented in the data segments of the kernel's program code. (here, counting the data segments of loadable module code as the same)
Note 2: You will not see "RAMdisk" in that file system list because it is a device, not a file system.
{rant}
There is an embedded Linux development firm out there even more screwed up than lab126 who implements a swap-file in a FAT-32 file system placed on a RAMdisk device.
A really useless idea.
{/rant}