From: CSRG <csrg@ucbvax.Berkeley.EDU>
Date: Mon, 26 Sep 1983 06:59:57 +0000 (-0800)
Subject: BSD 4_2 development
X-Git-Tag: BSD-4_3^2~74
X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/commitdiff_plain/f620aa1dbe5243cddbac940a73e40351b385c65a

BSD 4_2 development
Work on file usr/man/man8/bad144.8

Synthesized-from: CSRG/cd1/4.2
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+.TH BAD144 8 "18 July 1983"
+.UC 4
+.SH NAME
+bad144 \- read/write dec standard 144 bad sector information
+.SH SYNOPSIS
+.B /etc/bad144
+[
+.B \-f
+]
+disktype disk
+[ sno [
+bad ...
+] ]
+.SH DESCRIPTION
+.I 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 format of
+the information is specified by DEC standard 144, as follows.
+.PP
+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
+.I dkbad
+structure.
+.PP
+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.
+.PP
+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.
+.PP
+The bad sector structure is as follows:
+.PP
+.ta .75i 1.5i 3.5i
+.nf
+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];
+};
+.fi
+.PP
+Unused slots in the
+.I bt_bad
+array are filled with all bits set, a putatively
+illegal value.
+.PP
+.I Bad144
+is invoked by giving a device type (e.g. rk07, rm03, rm05, etc.), and a device
+name (e.g. hk0, hp1, etc.).  It reads the first sector of the last track
+of the corresponding 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 sectors, and will then write the supplied information onto the
+same location.  Note, however, that 
+.I bad144
+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 necessary to reboot before the change will take effect.
+.PP
+If the disk is an RP06, Fujitsu Eagle,
+or Ampex Capricorn on a Massbus, the
+.B \-f
+option may be used to mark the bad sectors as ``bad''.
+\fBNOTE:  this can only be done safely when there is no other disk activity\fP,
+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 sectors 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.
+.SH SEE ALSO
+badsect(8),
+format(8V)
+.SH BUGS
+It should be possible to format disks on-line under UNIX.
+.PP
+It should be possible to mark bad sectors on drives of all type.
+.PP
+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.
+.PP
+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.