Documentation/filesystems/ubifs.rst

1 .. SPDX-License-Identifier: GPL-2.0
10 UBIFS file-system stands for UBI File System. UBI stands for "Unsorted
13 is completely different to any traditional file-system in Linux, like
14 Ext2, XFS, JFS, etc. UBIFS represents a separate class of file-systems
16 file-system of this class is JFFS2.
24 2 MTD devices support 3 main operations - read from some offset within an
26   eraseblock. Block  devices support 2 main operations - read a whole
29   re-write its contents. Blocks may be just re-written.
30 4 Eraseblocks become worn out after some number of erase cycles -
31   typically 100K-1G for SLC NAND and NOR flashes, and 1K-10K for MLC
32   NAND flashes. Blocks do not have the wear-out property.
39 file-systems.
43 wear-leveling layer. It provides so called UBI volumes which is a higher
45 is very similar to MTD devices - they still consist of large eraseblocks,
47 limitations like wear and bad blocks (items 4 and 5 in the above list).
49 In a sense, UBIFS is a next generation of JFFS2 file-system, but it is
55 * JFFS2 does not have on-media index and has to build it while mounting,
59 * JFFS2 is a write-through file-system, while UBIFS supports write-back,
62 Similarly to JFFS2, UBIFS supports on-the-fly compression which makes
65 Similarly to JFFS2, UBIFS is tolerant of unclean reboots and power-cuts.
67 journal and recovers from crashes, ensuring that the on-flash data
91 no_bulk_read (*)	do not bulk-read
120     $ mount -t ubifs ubi0_0 /mnt/ubifs
125     $ mount -t ubifs ubi0:rootfs /mnt/ubifs
136 - http://www.linux-mtd.infradead.org/doc/ubifs.html
137 - http://www.linux-mtd.infradead.org/faq/ubifs.html