In reply to:

---

Does mke2fs always put a backup superblock at 8193?

---

Dunno - I admit to being on guesswork here.

Here's what the e2fsck manpage on my workstation says:

-b superblock

Instead of using the normal superblock, use an alternative superblock specified by superblock. This option is normally used when the primary superblock has been corrupted. The location of the backup superblock is dependent on the filesystem's blocksize. For filesystems with 1k blocksizes, a backup superblock can be found at block 8193; for filesystems with 2k blocksizes, at block 16384; and for 4k blocksizes, at block 32768.

Additional backup superblocks can be determined by using the mke2fs program using the -n option to print out where the superblocks were created. The -b option to mke2fs, which specifies blocksize of the filesystem must be specified in order for the superblock locations that are printed out to be accurate.

If an alternative superblock is specified and the filesystem is not opened read-only, e2fsck will make sure that the primary superblock is updated appropriately upon completion of the filesystem check.

In reply to:

---

There isn't even a "mke2fs --dry-run" that tells you where it's putting them.

---

"man mke2fs" says:

-n causes mke2fs to not actually create a filesystem, but display what it would do if it were to create a filesystem.

Does that not tell you where the superblocks are going? What if you also use -v?

Also,looking at the mke2fs manpage, it mentions rebuilding the superblock if you know the right parameters, using the -S option. Anyone know what incantation to use this on the Empeg?