4.3BSD-UWisc/man/cat8/bad144.8
BAD144(8) UNIX Programmer's Manual 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
_B_a_d_1_4_4 can be used to inspect the information stored on a
disk that is used by the disk drivers to implement bad sec-
tor forwarding. The format of the information is specified
by DEC standard 144, as follows.
The bad sector information is located in the first 5 even
numbered sectors of the last track of the disk pack. There
are five identical copies of the information, described by
the _d_k_b_a_d structure.
Replacement sectors are allocated starting with the first
sector before the bad sector information and working back-
wards 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 con-
ventionally 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 _b_t__b_a_d array are filled with all bits
set, a putatively illegal value.
Printed 12/27/86 May 20, 1986 1
BAD144(8) UNIX Programmer's Manual BAD144(8)
_B_a_d_1_4_4 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 arguments it reads the first sector of the last
track of the corresponding disk and prints out the bad sec-
tor information. It issues a warning if the bad sectors are
out of order. _B_a_d_1_4_4 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, how-
ever, that _b_a_d_1_4_4 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 information 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 accommodate the additions;
the new replacement sectors are cleared. The entire process
is described as it happens in gory detail if -v (verbose) is
given. The -c option forces an attempt to copy the old sec-
tor to the replacement, and may be useful when replacing an
unreliable sector.
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 sec-
tors. 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
Printed 12/27/86 May 20, 1986 2
BAD144(8) UNIX Programmer's Manual BAD144(8)
free of errors and bad sectors.
Printed 12/27/86 May 20, 1986 3