bad144 man page on Ultrix

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bad144(8)							     bad144(8)

Name
       bad144 - read/write DEC Standard 144 bad sector information

Syntax
       /etc/bad144 [ -f ] disktype disk [ sno [ bad ...	 ] ]

Description
       The  command  can  be  used to inspect the information stored on a disk
       that is used by the disk drivers to implement  bad  sector  forwarding.
       The format of the information is specified by DEC Standard 144, as fol‐
       lows.

       The bad sector information is located in the first five	even  numbered
       sectors	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 which replacement
       sector it corresponds to.  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.

       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, an
       accepted illegal value.

       The command is invoked by giving a  device  type	 (for  example,	 rk07,
       rm03,  rm05,  and  so forth), and a device name (for example, hk0, hp1,
       and so forth).  It reads the first sector of the last track of the cor‐
       responding disk and prints out the bad sector information.  It may also
       be invoked giving a serial number for the pack and a list of  bad  sec‐
       tors,  and will then write the supplied information onto the same loca‐
       tion.  Note, however, that does not arrange for the  specified  sectors
       to  be  marked  bad  in	this case.  This option should only be used to
       restore known bad sector information which was destroyed.  It is neces‐
       sary to reboot before the change will take effect.

       If the disk is an RP06, Fujitsu Eagle, or Ampex Capricorn on a Massbus,
       the -f option may be used to mark the bad sectors as ``bad''.  This can
       only  be	 done  safely when there is no other disk activity, preferably
       while running single-user.  Otherwise, new bad  sectors	can  be	 added
       only  by running a formatter.  Note that the order in which the sectors
       are listed determines which sectors used for replacements.  If new sec‐
       tors  are  being inserted into the list on a drive that is in use, care
       should be taken that replacements for existing  bad  sectors  have  the
       correct contents.

Restrictions
       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.

See Also
       badsect(8), format(8v)

				      VAX			     bad144(8)
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