1.\" FreeBSD version Copyright (c) 1996 2.\" Mike Pritchard <mpp@FreeBSD.org>. All rights reserved. 3.\" 4.\" Adapted from share/man/man8/man8.hp300/crash.8 5.\" 6.\" Copyright (c) 1990, 1991, 1993 7.\" The Regents of the University of California. All rights reserved. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the University of 20.\" California, Berkeley and its contributors. 21.\" 4. Neither the name of the University nor the names of its contributors 22.\" may be used to endorse or promote products derived from this software 23.\" without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35.\" SUCH DAMAGE. 36.\" 37.\" $FreeBSD: src/share/man/man8/crash.8,v 1.22 2005/06/30 13:01:44 hmp Exp $ 38.\" $DragonFly: src/share/man/man8/crash.8,v 1.7 2007/10/16 08:49:38 swildner Exp $ 39.\" 40.Dd February 2, 1996 41.Dt CRASH 8 42.Os 43.Sh NAME 44.Nm crash 45.Nd 46.Dx 47system failures 48.Sh DESCRIPTION 49This section explains a bit about system crashes 50and (very briefly) how to analyze crash dumps. 51.Pp 52When the system crashes voluntarily it prints a message of the form 53.Bl -diag -offset indent 54.It "panic: why i gave up the ghost" 55.El 56.Pp 57on the console, and if dumps have been enabled (see 58.Xr dumpon 8 ) , 59takes a dump on a mass storage peripheral, 60and then invokes an automatic reboot procedure as 61described in 62.Xr reboot 8 . 63Unless some unexpected inconsistency is encountered in the state 64of the file systems due to hardware or software failure, the system 65will then resume multi-user operations. 66.Pp 67The system has a large number of internal consistency checks; if one 68of these fails, then it will panic with a very short message indicating 69which one failed. 70In many instances, this will be the name of the routine which detected 71the error, or a two-word description of the inconsistency. 72A full understanding of most panic messages requires perusal of the 73source code for the system. 74.Pp 75The most common cause of system failures is hardware failure, which 76can reflect itself in different ways. 77Here are the messages which 78are most likely, with some hints as to causes. 79Left unstated in all cases is the possibility that hardware or software 80error produced the message in some unexpected way. 81.Pp 82.Bl -diag -compact 83.It "cannot mount root" 84This panic message results from a failure to mount the root file system 85during the bootstrap process. 86Either the root file system has been corrupted, 87or the system is attempting to use the wrong device as root file system. 88Usually, an alternate copy of the system binary or an alternate root 89file system can be used to bring up the system to investigate. 90Most often this is done using the 91.Dx 92.Dq LiveCD . 93.Pp 94.It "init: not found" 95This is not a panic message, as reboots are likely to be futile. 96Late in the bootstrap procedure, the system was unable to locate 97and execute the initialization process, 98.Xr init 8 . 99The root file system is incorrect or has been corrupted, or the mode 100or type of 101.Pa /sbin/init 102forbids execution or is totally missing. 103.Pp 104.It "ffs_realloccg: bad optim" 105.It "ffs_valloc: dup alloc" 106.It "ffs_alloccgblk: cyl groups corrupted" 107.It "ffs_alloccg: map corrupted" 108.It "blkfree: freeing free block" 109.It "blkfree: freeing free frag" 110.It "ifree: freeing free inode" 111These panic messages are among those that may be produced 112when file system inconsistencies are detected. 113The problem generally results from a failure to repair damaged file systems 114after a crash, hardware failures, or other condition that should not 115normally occur. 116A file system check will normally correct the problem. 117.Pp 118.It "timeout table full" 119This really should not be a panic, but until the data structure 120involved is made to be extensible, running out of entries causes a crash. 121If this happens, make the timeout table bigger. 122.Pp 123.It "init died (signal #, exit #)" 124The system initialization process has exited with the specified 125signal number and exit code. 126This is bad news, as no new users will then be able to log in. 127Rebooting is the only fix, so the 128system just does it right away. 129.El 130.Pp 131That completes the list of panic types you are likely to see. 132.Pp 133If the system has been configured to take crash dumps (see 134.Xr dumpon 8 ) , 135then when it crashes it will write (or at least attempt to write) 136an image of memory into the back end of the dump device, 137usually the same as the primary swap 138area. 139After the system is rebooted, the program 140.Xr savecore 8 141runs and preserves a copy of this core image and the current 142system in a specified directory for later perusal. 143See 144.Xr savecore 8 145for details. 146.Pp 147To analyze a dump you should begin by running 148.Xr kgdb 1 149on the system load image and core dump. 150If the core image is the result of a panic, 151the panic message is printed. 152For more details consult the chapter on kernel debugging in 153the 154.%B "FreeBSD Developers' Handbook" 155.Pq Pa http://www.FreeBSD.org/ . 156.Sh SEE ALSO 157.Xr kgdb 1 , 158.Xr dumpon 8 , 159.Xr reboot 8 , 160.Xr savecore 8 161.Sh HISTORY 162The 163.Nm 164manual page first appeared in 165.Fx 2.2 . 166