BADSECT(8) OpenBSD System Manager's Manual BADSECT(8)
badsect - create files to contain bad sectors
badsect bbdir sector [...]
badsect makes a file to contain a bad sector. Normally, bad sectors are
made inaccessible by the standard formatter, which provides a forwarding
table for bad sectors to the driver; see bad144(8) for details. If a
driver supports the bad blocking standard, it is much more preferable to
use that method to isolate bad blocks, since the bad block forwarding
makes the pack appear perfect, and such packs can then be copied with
dd(1). The technique used by this program is also less general than bad
block forwarding, as badsect can't make amends for bad blocks in the i-
list of file systems or in swap areas.
On some disks, adding a sector which is suddenly bad to the bad sector
table currently requires the running of the standard DEC formatter. Thus
to deal with a newly bad block or on disks where the drivers do not sup-
port the bad-blocking standard badsect may be used to good effect.
badsect is used on a quiet file system in the following way: First mount
the file system, and change to its root directory. Make a directory BAD
there. Run badsect, giving as argument the BAD directory followed by all
the bad sectors you wish to add. (The sector numbers must be relative to
the beginning of the file system, but this is not hard as the system re-
ports relative sector numbers in its console error messages.) Then
change back to the root directory, unmount the file system and run
fsck(8) on the file system. The bad sectors should show up in two files
or in the bad sector files and the free list. Have fsck remove files
containing the offending bad sectors, but do not have it remove the
BAD/nnnnn files. This will leave the bad sectors in only the BAD files.
badsect works by giving the specified sector numbers in a mknod(2) system
call, creating an illegal file whose first block address is the block
containing the bad sector, and whose name is the bad sector number. When
it is discovered by fsck it will ask ``HOLD BAD BLOCK?'' A positive re-
sponse will cause fsck to convert the inode to a regular file containing
the bad block.
badsect refuses to attach a block that resides in a critical area or is
out of range of the file system. A warning is issued if the block is al-
ready in use.
The badsect command appeared in 4.1BSD.
If more than one sector which comprises a file system fragment is bad,
you should specify only one of them to badsect, as the blocks in the bad
sector files actually cover all the sectors in a file system fragment.
OpenBSD 3.6 June 5, 1993 1