Correct manual page, based on feedback from Bruce Evans.
Reviewed by: Bruce Evans <bde@freebsd.org>
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svn path=/head/; revision=36414
@ -30,7 +30,7 @@
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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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.\" $Id: dumpon.8,v 1.5 1997/02/22 14:32:21 peter Exp $
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.\" $Id: dumpon.8,v 1.6 1998/05/25 08:54:40 jkoshy Exp $
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.\"
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.Dd May 12, 1995
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.Dt DUMPON 8
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@ -41,45 +41,45 @@
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.Sh SYNOPSIS
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.Nm dumpon
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.Op Fl v
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.Ar swap_device
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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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The system begins with no dump area configured for safety. If a
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.Dq dumps on
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clause is specified in the kernel configuration file
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or if the variable
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.Dq Li dumpdev
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in the boot time configuration file
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.Pa /etc/rc.conf
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names a dump device, future panics will cause the kernel
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to save a crash dump on the specified dump device.
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The dump device must be one of the swap areas
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specified in the filesystem configuration file
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.Pa /etc/fstab ,
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and it must be at least the size of physical memory.
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.Pp
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Calls to
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.Nm dumpon
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normally occur in the system multi-user initialization file
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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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before the
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.Xr savecore 8
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program is run.
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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 can be specified to cause the
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flag causes
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.Nm
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program to be verbose about its activity.
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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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Hardcoding the dump device using the kernel configuration file
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is only useful if a kernel crashes before reaching multi-user mode.
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Otherwise, the use of
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The dump device can also be specified at kernel compile time using
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the
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.Dq dumps on
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clause in the kernel configuration file (see
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.Xr config 8 ).
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This is useful when the kernel panics before multi-user mode
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is reached. Subsequent successful invocations of
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.Nm
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to specify the dump device is recommended.
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will override the compiled in value.
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.Pp
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The
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.Nm
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@ -93,7 +93,7 @@ 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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is the text string:
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.Dq Li off .
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.Sh SEE ALSO
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.Xr sysctl 3 ,
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@ -109,14 +109,16 @@ is the text string
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.Bl -tag -width /dev/[ws]d?b -compact
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.It Pa /dev/[ws]d?b
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standard swap areas
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.It Pa /etc/fstab
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static filesystem and swap information
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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
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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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