mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-24 11:29:10 +00:00
138 lines
5.4 KiB
Perl
138 lines
5.4 KiB
Perl
.\" Copyright (c) 1983, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)b.t 8.1 (Berkeley) 6/8/93
|
|
.\"
|
|
.\".ds RH "Device Defaulting Rules
|
|
.bp
|
|
.LG
|
|
.B
|
|
.ce
|
|
APPENDIX B. RULES FOR DEFAULTING SYSTEM DEVICES
|
|
.sp
|
|
.R
|
|
.NL
|
|
.PP
|
|
When \fIconfig\fP processes a ``config'' rule which does
|
|
not fully specify the location of the root file system,
|
|
paging area(s), device for system dumps, and device for
|
|
argument list processing it applies a set of rules to
|
|
define those values left unspecified. The following list
|
|
of rules are used in defaulting system devices.
|
|
.IP 1) 3
|
|
If a root device is not specified, the swap
|
|
specification must indicate a ``generic'' system is to be built.
|
|
.IP 2) 3
|
|
If the root device does not specify a unit number, it
|
|
defaults to unit 0.
|
|
.IP 3) 3
|
|
If the root device does not include a partition specification,
|
|
it defaults to the ``a'' partition.
|
|
.IP 4) 3
|
|
If no swap area is specified, it defaults to the ``b''
|
|
partition of the root device.
|
|
.IP 5) 3
|
|
If no device is specified for processing argument lists, the
|
|
first swap partition is selected.
|
|
.IP 6) 3
|
|
If no device is chosen for system dumps, the first swap
|
|
partition is selected (see below to find out where dumps are
|
|
placed within the partition).
|
|
.PP
|
|
The following table summarizes the default partitions selected
|
|
when a device specification is incomplete, e.g. ``hp0''.
|
|
.DS
|
|
.TS
|
|
l l.
|
|
Type Partition
|
|
_
|
|
root ``a''
|
|
swap ``b''
|
|
args ``b''
|
|
dumps ``b''
|
|
.TE
|
|
.DE
|
|
.SH
|
|
Multiple swap/paging areas
|
|
.PP
|
|
When multiple swap partitions are specified, the system treats the
|
|
first specified as a ``primary'' swap area which is always used.
|
|
The remaining partitions are then interleaved into the paging
|
|
system at the time a
|
|
.IR swapon (2)
|
|
system call is made. This is normally done at boot time with
|
|
a call to
|
|
.IR swapon (8)
|
|
from the /etc/rc file.
|
|
.SH
|
|
System dumps
|
|
.PP
|
|
System dumps are automatically taken after a system crash,
|
|
provided the device driver for the ``dumps'' device supports
|
|
this. The dump contains the contents of memory, but not
|
|
the swap areas. Normally the dump device is a disk in
|
|
which case the information is copied to a location at the
|
|
back of the partition. The dump is placed in the back of the
|
|
partition because the primary swap and dump device are commonly
|
|
the same device and this allows the system to be rebooted without
|
|
immediately overwriting the saved information. When a dump has
|
|
occurred, the system variable \fIdumpsize\fP
|
|
is set to a non-zero value indicating the size (in bytes) of
|
|
the dump. The \fIsavecore\fP\|(8)
|
|
program then copies the information from the dump partition to
|
|
a file in a ``crash'' directory and also makes a copy of the
|
|
system which was running at the time of the crash (usually
|
|
``/vmunix''). The offset to the system dump is defined in the
|
|
system variable \fIdumplo\fP (a sector offset from
|
|
the front of the dump partition). The
|
|
.I savecore
|
|
program operates by reading the contents of \fIdumplo\fP, \fIdumpdev\fP,
|
|
and \fIdumpmagic\fP from /dev/kmem, then comparing the value
|
|
of \fIdumpmagic\fP read from /dev/kmem to that located in
|
|
corresponding location in the dump area of the dump partition.
|
|
If a match is found,
|
|
.I savecore
|
|
assumes a crash occurred and reads \fIdumpsize\fP from the dump area
|
|
of the dump partition. This value is then used in copying the
|
|
system dump. Refer to
|
|
\fIsavecore\fP\|(8)
|
|
for more information about its operation.
|
|
.PP
|
|
The value \fIdumplo\fP is calculated to be
|
|
.DS
|
|
\fIdumpdev-size\fP \- \fImemsize\fP
|
|
.DE
|
|
where \fIdumpdev-size\fP is the size of the disk partition
|
|
where system dumps are to be placed, and
|
|
\fImemsize\fP is the size of physical memory.
|
|
If the disk partition is not large enough to hold a full
|
|
dump, \fIdumplo\fP is set to 0 (the start of the partition).
|