badsect - create files to contain bad sectors
badsect bbdir sector ...
The badsect utility 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. If a driver supports the
bad blocking standard it is much 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 cannot
make amends for bad blocks in the i-list of file systems or in swap
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
support the bad-blocking standard badsect may be used to good effect.
The badsect utility 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 reports 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(8) 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.
The badsect utility 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 bad sector and whose name is the bad sector
number. When it is discovered by fsck(8) it will ask “HOLD BAD BLOCK ?”.
A positive response will cause fsck(8) to convert the inode to a regular
file containing the bad block.
The badsect utility 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 already in use.
The badsect utility appeared in 4.1BSD.
If more than one sector which comprise a file system fragment are 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.