ubifs- superblock

The first LEB is not LEB one, it is LEB zero. LEB zero stores the superblock node. The superblock node contains file system parameters that change rarely if at all.

For example, the flash geometry (eraseblock size, number of eraseblocks etc) is stored in the superblock node.At present, there is only one situation where the superblock node gets rewritten, which is when an automatic resize occurs.

UBIFS presently has a very limited ability to resize to grow bigger, but only to a maximum size specified when the file system is created. This mechanism is needed because theactual size of a flash partition varies due to the presence of a variable number of bad eraseblocks.

So when a file system image is created by mkfs.ubifs, the maximum number of eraseblocks is specified and the image records this, and the actual number of eraseblocks used, in the superblock node.

When UBIFS is mounted on a partition (actually a UBI volume), if the number of eraseblocks is greater than that recorded in the superblock node and less than the maximum number of eraseblocks (also recorded in the superblock node), then the UBIFS file system is automatically

resized to fit the partition (UBI volume).