4.3BSD - /usr/man/cat8/bad144.0

BAD144(8)                                                            BAD144(8)


NAME
       bad144 - read/write dec standard 144 bad sector information

SYNOPSIS
       /etc/bad144 [ -f ] [ -c ] [ -v ] disktype disk [ sno [ bad ...  ] ]
       /etc/bad144 -a [ -f ] [ -c ] [ -v ] disktype disk [ bad ...  ]

DESCRIPTION
       Bad144  can be used to inspect the information stored on a disk that is
       used by the disk drivers to implement bad sector forwarding.  The  for‐
       mat of the information is specified by DEC standard 144, as follows.

       The bad sector information is located in the first 5 even numbered sec‐
       tors of the last track of the disk  pack.   There  are  five  identical
       copies of the information, described by the dkbad structure.

       Replacement sectors are allocated starting with the first sector before
       the bad sector information and working backwards towards the  beginning
       of the disk.  A maximum of 126 bad sectors are supported.  The position
       of the bad sector in the bad sector table  determines  the  replacement
       sector  to  which  it  corresponds.   The bad sectors must be listed in
       ascending order.

       The bad sector information and replacement sectors  are  conventionally
       only  accessible  through  the ‘‘c’’ file system partition of the disk.
       If that partition is used for a file system, the  user  is  responsible
       for  making sure that it does not overlap the bad sector information or
       any replacement sectors.  Thus, one track  plus  126  sectors  must  be
       reserved to allow use of all of the possible bad sector replacements.

       The bad sector structure is as follows:

       struct dkbad {
              long    bt_csn;             /* cartridge serial number */
              u_short bt_mbz;             /* unused; should be 0 */
              u_short bt_flag;            /* -1 => alignment cartridge */
              struct bt_bad {
                      u_short bt_cyl;     /* cylinder number of bad sector */
                      u_short bt_trksec;  /* track and sector number */
              } bt_bad[126];
       };

       Unused  slots in the bt_bad array are filled with all bits set, a puta‐
       tively illegal value.

       Bad144 is invoked by giving a  device  type  (e.g.  rk07,  rm03,  rm05,
       etc.), and a device name (e.g. hk0, hp1, etc.).  With no optional argu‐
       ments it reads the first sector of the last track of the  corresponding
       disk and prints out the bad sector information.  It issues a warning if
       the bad sectors are out of order.  Bad144 may also be  invoked  with  a
       serial  number  for  the pack and a list of bad sectors.  It will write
       the supplied information  into  all  copies  of  the  bad-sector  file,
       replacing  any  previous  information.  Note, however, that bad144 does
       not arrange for the specified sectors to be marked bad  in  this  case.
       This procedure should only be used to restore known bad sector informa‐
       tion which was destroyed.  It is necessary to reboot before any  change
       will take effect.

       With the -a option, the argument list consists of new bad sectors to be
       added to an existing list.  The new sectors are sorted into  the  list,
       which must have been in order.  Replacement sectors are moved to accom‐
       modate the additions; the new replacement  sectors  are  cleared.   The
       entire  process  is  described as it happens in gory detail if -v (ver‐
       bose) is given.  The -c option forces an attempt to copy the old sector
       to the replacement, and may be useful when replacing an unreliable sec‐
       tor.

       If the disk is an RP06, RM03, RM05, Fujitsu Eagle, or  SMD  disk  on  a
       Massbus,  the  -f  option  may  be  used to mark the new bad sectors as
       ‘‘bad’’ by reformatting them as unusable sectors.  NOTE:  this  can  be
       done safely only when there is no other disk activity, preferably while
       running single-user.  This option is required unless the  sectors  have
       already  been  marked  bad,  or the system will not be notified that it
       should use the replacement sector.

SEE ALSO
       badsect(8), format(8V)

BUGS
       It should be possible to format disks on-line under UNIX.

       It should be possible to mark bad sectors on drives of all type.

       On an 11/750, the standard bootstrap drivers used to boot the system do
       not understand bad sectors, handle ECC errors, or the special SSE (skip
       sector) errors of RM80-type disks.   This  means  that  none  of  these
       errors  can  occur when reading the file /vmunix to boot.  Sectors 0-15
       of the disk drive must also not have any of these errors.

       The drivers which write a system core image on disk after  a  crash  do
       not  handle errors; thus the crash dump area must be free of errors and
       bad sectors.


4th Berkeley Distribution        May 20, 1986                        BAD144(8)