480f31c214
Changes include modifications in kernel crash dump routines, dumpon(8) and savecore(8). A new tool called decryptcore(8) was added. A new DIOCSKERNELDUMP I/O control was added to send a kernel crash dump configuration in the diocskerneldump_arg structure to the kernel. The old DIOCSKERNELDUMP I/O control was renamed to DIOCSKERNELDUMP_FREEBSD11 for backward ABI compatibility. dumpon(8) generates an one-time random symmetric key and encrypts it using an RSA public key in capability mode. Currently only AES-256-CBC is supported but EKCD was designed to implement support for other algorithms in the future. The public key is chosen using the -k flag. The dumpon rc(8) script can do this automatically during startup using the dumppubkey rc.conf(5) variable. Once the keys are calculated dumpon sends them to the kernel via DIOCSKERNELDUMP I/O control. When the kernel receives the DIOCSKERNELDUMP I/O control it generates a random IV and sets up the key schedule for the specified algorithm. Each time the kernel tries to write a crash dump to the dump device, the IV is replaced by a SHA-256 hash of the previous value. This is intended to make a possible differential cryptanalysis harder since it is possible to write multiple crash dumps without reboot by repeating the following commands: # sysctl debug.kdb.enter=1 db> call doadump(0) db> continue # savecore A kernel dump key consists of an algorithm identifier, an IV and an encrypted symmetric key. The kernel dump key size is included in a kernel dump header. The size is an unsigned 32-bit integer and it is aligned to a block size. The header structure has 512 bytes to match the block size so it was required to make a panic string 4 bytes shorter to add a new field to the header structure. If the kernel dump key size in the header is nonzero it is assumed that the kernel dump key is placed after the first header on the dump device and the core dump is encrypted. Separate functions were implemented to write the kernel dump header and the kernel dump key as they need to be unencrypted. The dump_write function encrypts data if the kernel was compiled with the EKCD option. Encrypted kernel textdumps are not supported due to the way they are constructed which makes it impossible to use the CBC mode for encryption. It should be also noted that textdumps don't contain sensitive data by design as a user decides what information should be dumped. savecore(8) writes the kernel dump key to a key.# file if its size in the header is nonzero. # is the number of the current core dump. decryptcore(8) decrypts the core dump using a private RSA key and the kernel dump key. This is performed by a child process in capability mode. If the decryption was not successful the parent process removes a partially decrypted core dump. Description on how to encrypt crash dumps was added to the decryptcore(8), dumpon(8), rc.conf(5) and savecore(8) manual pages. EKCD was tested on amd64 using bhyve and i386, mipsel and sparc64 using QEMU. The feature still has to be tested on arm and arm64 as it wasn't possible to run FreeBSD due to the problems with QEMU emulation and lack of hardware. Designed by: def, pjd Reviewed by: cem, oshogbo, pjd Partial review: delphij, emaste, jhb, kib Approved by: pjd (mentor) Differential Revision: https://reviews.freebsd.org/D4712
186 lines
5.0 KiB
Groff
186 lines
5.0 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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.\" 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: @(#)savecore.8 8.1 (Berkeley) 6/5/93
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.\" $FreeBSD$
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.\"
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.Dd December 10, 2016
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.Dt SAVECORE 8
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.Os
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.Sh NAME
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.Nm savecore
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.Nd "save a core dump of the operating system"
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.Sh SYNOPSIS
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.Nm
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.Fl c
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.Op Fl v
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.Op Ar device ...
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.Nm
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.Fl C
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.Op Fl v
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.Op Ar device ...
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.Nm
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.Op Fl -libxo
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.Op Fl fkvz
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.Op Fl m Ar maxdumps
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.Op Ar directory Op Ar device ...
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.Sh DESCRIPTION
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The
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.Nm
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utility
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copies a core dump into
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.Ar directory ,
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or the current working directory if no
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.Ar directory
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argument is given,
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and enters a reboot message and information about the core dump into
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the system log.
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.Pp
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The options are as follows:
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.Bl -tag -width ".Fl m Ar maxdumps"
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.It Fl -libxo
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Generate output via
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.Xr libxo 3
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in a selection of different human and machine readable formats.
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See
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.Xr xo_parse_args 3
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for details on command line arguments.
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.It Fl C
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Check to see if a dump exists,
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and display a brief message to indicate the status.
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An exit status of 0 indicates that a dump is there,
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1 indicates that none exists.
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This option is compatible only with the
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.Op Fl v
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option.
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.It Fl c
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Clear the dump, so that future invocations of
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.Nm
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will ignore it.
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.It Fl f
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Force a dump to be taken even if either the dump was cleared or if the
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dump header information is inconsistent.
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.It Fl k
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Do not clear the dump after saving it.
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.It Fl m Ar maxdumps
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Maximum number of dumps to store.
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Once the number of stored dumps is equal to
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.Ar maxdumps
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the counter will restart from
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.Dv 0 .
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.It Fl v
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Print out some additional debugging information.
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Specify twice for more information.
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.It Fl z
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Compress the core dump and kernel (see
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.Xr gzip 1 ) .
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.El
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.Pp
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The
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.Nm
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utility
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looks for dumps on each device specified by the
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.Ar device
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argument(s), or on each device in
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.Pa /etc/fstab
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marked as
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.Dq dump
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or
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.Dq swap .
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The
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.Nm
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utility
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checks the core dump in various ways to make sure that it is complete.
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If it passes these checks, it saves the core image in
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.Ar directory Ns Pa /vmcore.#
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and information about the core in
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.Ar directory Ns Pa /info.# .
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If the core is encrypted, it saves the dump key in
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.Ar directory Ns Pa /key.# .
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The core can be later decrypted using
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.Xr decryptcore 8 .
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For kernel textdumps generated with the
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.Xr textdump 4
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facility, output will be stored in the
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.Xr tar 5
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format and named
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.Ar directory Ns Pa /textdump.tar.# .
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The
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.Dq #
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is the number from the first line of the file
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.Ar directory Ns Pa /bounds ,
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and it is incremented and stored back into the file each time
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.Nm
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successfully runs.
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.Pp
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The
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.Nm
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utility
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also checks the available disk space before attempting to make the copies.
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If there is insufficient disk space in the file system containing
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.Ar directory ,
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or if the file
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.Ar directory Ns Pa /minfree
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exists and the number of free kilobytes (for non-superusers) in the
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file system after the copies were made would be less than the number
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in the first line of this file, the copies are not attempted.
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.Pp
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If
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.Nm
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successfully copies the kernel and the core dump, the core dump is cleared
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so that future invocations of
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.Nm
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will ignore it.
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.Pp
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The
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.Nm
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utility
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is meant to be called near the end of the initialization file
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.Pa /etc/rc
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(see
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.Xr rc 8 ) .
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.Sh SEE ALSO
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.Xr gzip 1 ,
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.Xr getbootfile 3 ,
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.Xr libxo 3 ,
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.Xr xo_parse_args 3 ,
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.Xr textdump 4 ,
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.Xr tar 5 ,
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.Xr decryptcore 8 ,
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.Xr dumpon 8 ,
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.Xr syslogd 8
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.Sh HISTORY
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The
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.Nm
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utility appeared in
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.Bx 4.1 .
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.Pp
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Support for kernel textdumps appeared in
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.Fx 7.1 .
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.Sh BUGS
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The minfree code does not consider the effect of compression or sparse files.
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