BADSECT(8)          UNIX Programmer's Manual           BADSECT(8)

NAME
     badsect - create files to contain bad sectors

SYNOPSIS
     /etc/badsect sector ...

DESCRIPTION
     _B_a_d_s_e_c_t 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 _b_a_d_1_4_4(8) for details.  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 _d_d(1).  The technique used by this program is
     also less general than bad block forwarding, as _b_a_d_s_e_c_t
     can't make amends for bad blocks in the i-list of file sys-
     tems or in swap areas.

     Adding a sector which is suddenly bad to the bad sector
     table currently requires the running of the standard DEC
     formatter, as UNIX does not supply formatters.  Thus to deal
     with a newly bad block or on disks where the drivers do not
     support the bad-blocking standard _b_a_d_s_e_c_t may be used to
     good effect.

     _B_a_d_s_e_c_t is used on a quiet file system in the following way:
     First mount the file system, and change to its root direc-
     tory.  Make a directory BAD there and change into it.  Run
     badsect giving as argument all the bad sectors you wish to
     add.  (The sector numbers should be given as physical disk
     sectors relative to the beginning of the file system,
     exactly as the system reports the sector numbers in its con-
     sole error messages.) Then change back to the root direc-
     tory, unmount the file system and run _f_s_c_k(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 _f_s_c_k remove
     files containing the offending bad sectors, but do not have
     it remove the BAD/_n_n_n_n_n files.  This will leave the bad sec-
     tors in only the BAD files.

     _B_a_d_s_e_c_t works by giving the specified sector numbers in a
     _m_k_n_o_d(2) system call (after taking into account the
     filesystem's block size), creating a regular file whose
     first block address is the block containing bad sector and
     whose name is the bad sector number.  The file has 0 length,
     but the check programs will still consider it to contain the
     block containing the sector.  This has the pleasant effect
     that the sector is completely inaccessible to the containing
     file system since it is not available by accessing the file.

Printed 8/2/83                                                  1

BADSECT(8)          UNIX Programmer's Manual           BADSECT(8)

SEE ALSO
     mknod(2), bad144(8), fsck(8)

BUGS
     If both sectors which comprise a (1024 byte) disk block are
     bad, you should specify only one of them to _b_a_d_s_e_c_t, as the
     blocks in the bad sector files actually cover both (bad)
     disk sectors.

     On the PDP-11, only sector number less than 131072 may be
     specified on 1024-byte block filesystems, 65536 on 512-byte
     block filesystems.  This is because only a short int is
     passed to the system from _m_k_n_o_d.

Printed 8/2/83                                                  2