138 lines
3.9 KiB
Groff
138 lines
3.9 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgment:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" From: @(#)swapon.8 8.1 (Berkeley) 6/5/93
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.\" $FreeBSD$
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.\"
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.Dd May 12, 1995
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.Dt DUMPON 8
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.Os FreeBSD 2.1
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.Sh NAME
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.Nm dumpon
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.Nd "specify a device for crash dumps"
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.Sh SYNOPSIS
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.Nm dumpon
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.Op Fl v
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.Ar special_file
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.Nm dumpon
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.Op Fl v
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.Ar off
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.Sh DESCRIPTION
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.Nm Dumpon
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is used to specify a device where the kernel can save a crash dump in
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the case of a panic.
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.Pp
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Calls to
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.Nm
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normally occur from the system multi-user initialization file
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.Pa /etc/rc ,
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controlled by the
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.Dq dumpdev
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variable in the boot time configuration file
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.Pa /etc/rc.conf .
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.Pp
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The size of the specified dump device must be at least 64 KB greater the
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size of physical memory.
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.Pp
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The
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.Fl v
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flag causes
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.Nm
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to be verbose about its activity.
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.Sh NOTES
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One of the system swap devices is usually chosen as the dump device, as
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swap devices are the most likely to have the required space at dump time.
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.Pp
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The
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.Nm
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program operates by setting the
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.Xr sysctl 3
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MIB variable
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.Dq kern.dumpdev
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to the device number of the designated
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.Ar special_file
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or to
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.Dv NODEV
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(meaning that no dumps are to be taken) if
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.Ar special_file
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is the text string:
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.Dq Li off .
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.Pp
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The
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.Xr ddb 4
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interactive kernel debugger may be used
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to specify a device for crash dumps
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that occur in single-user mode.
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For example,
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the following command at the
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.Xr ddb 4
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prompt would return the device number for the swap device
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.Pa /dev/ad0s1b :
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.Bd -literal -offset ident
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show disk/ad0s1b
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.Ed
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.Pp
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The value returned could then be written to the
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.Va dumpdev
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kernel variable as follows:
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.Bd -literal -offset indent
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write dumpdev 0xc0b65800
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.Ed
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.Sh SEE ALSO
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.Xr sysctl 3 ,
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.Xr fstab 5 ,
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.Xr rc.conf 5 ,
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.Xr config 8 ,
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.Xr init 8 ,
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.Xr rc 8 ,
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.Xr savecore 8 ,
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.Xr swapon 8 ,
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.Xr panic 9
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.Sh FILES
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.Bl -tag -width "/dev/{wd,da}?s?b" -compact
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.It Pa /dev/{wd,da}?s?b
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standard swap areas
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.It Pa /etc/rc.conf
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boot-time system configuration
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.El
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.Sh BUGS
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Because the filesystem layer is already dead by the time a crash dump
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is taken, it is not possible to send crash dumps directly to a file.
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.Pp
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.Nm Dumpon
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currently allows only devices with minor number 1 to be used as dump
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devices.
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.Sh HISTORY
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The
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.Nm
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command appeared in
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.Fx 2.1 .
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