badsect - Creates files to contain bad sectors
/usr/sbin/badsect bbdir sector ...
The badsect command 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 preferable to use that method to isolate bad blocks because the bad block forwarding makes the disk appear perfect, and such disks can then be copied with dd(1). The technique used by badsect 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 areas.
On some disks, adding a sector that is suddenly bad to the bad sector table currently requires the running of the standard formatter. Thus, to deal with a newly bad block or on disks where the drivers do not support the bad-blocking standard, badsect can be used to good effect.
Use the badsect command on a quiet file system in the following way: 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, as reported in console error messages.) 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 operation will leave the bad sectors in only the BAD files.
The badsect command 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 fsck discovers the file, it will ask "HOLD BAD BLOCK?" An affirmative response will cause fsck to convert the inode to a regular file containing the bad block.
If more than one of the sectors comprised by a file system fragment are bad, you should specify only one to badsect, as the blocks in the bad sector files cover all the sectors in a file system fragment.
The badsect command 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.
Commands: fsck(8) delim off