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 1.9.2.5 2002/03/19 01:57:27 dd Exp $ 38.\" $DragonFly: src/share/man/man8/crash.8,v 1.4 2005/12/10 00:22:29 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.Bd -ragged -offset indent 54panic: why i gave up the ghost 55.Ed 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. Here are the messages which 77are most likely, with some hints as to causes. 78Left unstated in all cases is the possibility that hardware or software 79error produced the message in some unexpected way. 80.Pp 81.Bl -tag -width Ds -compact 82.It Sy "cannot mount root" 83This panic message results from a failure to mount the root filesystem 84during the bootstrap process. 85Either the root filesystem has been corrupted, 86or the system is attempting to use the wrong device as root filesystem. 87Usually, an alternate copy of the system binary or an alternate root 88filesystem can be used to bring up the system to investigate. Most often 89this is done by the use of the boot floppy you used to install the system, 90and then using the "fixit" floppy. 91.Pp 92.It Sy "init: not found" 93This is not a panic message, as reboots are likely to be futile. 94Late in the bootstrap procedure, the system was unable to locate 95and execute the initialization process, 96.Xr init 8 . 97The root filesystem is incorrect or has been corrupted, or the mode 98or type of 99.Pa /sbin/init 100forbids execution or is totally missing. 101.Pp 102.Pp 103.It Sy "ffs_realloccg: bad optim" 104.It Sy "ffs_valloc: dup alloc" 105.It Sy "ffs_alloccgblk: cyl groups corrupted" 106.It Sy "ffs_alloccg: map corrupted" 107.It Sy "blkfree: freeing free block" 108.It Sy "blkfree: freeing free frag" 109.It Sy "ifree: freeing free inode" 110These panic messages are among those that may be produced 111when filesystem inconsistencies are detected. 112The problem generally results from a failure to repair damaged filesystems 113after a crash, hardware failures, or other condition that should not 114normally occur. 115A filesystem check will normally correct the problem. 116.Pp 117.It Sy "timeout table full" 118This really shouldn't be a panic, but until the data structure 119involved is made to be extensible, running out of entries causes a crash. 120If this happens, make the timeout table bigger. 121.Pp 122.\" .It Sy "trap type %d, code = %x, v = %x" 123.\" An unexpected trap has occurred within the system; the trap types are: 124.\" .Bl -column xxxx -offset indent 125.\" 0 bus error 126.\" 1 address error 127.\" 2 illegal instruction 128.\" 3 divide by zero 129.\" .No 4\t Em chk No instruction 130.\" .No 5\t Em trapv No instruction 131.\" 6 privileged instruction 132.\" 7 trace trap 133.\" 8 MMU fault 134.\" 9 simulated software interrupt 135.\" 10 format error 136.\" 11 FP coprocessor fault 137.\" 12 coprocessor fault 138.\" 13 simulated AST 139.\" .El 140.\" .Pp 141.\" The favorite trap type in system crashes is trap type 8, 142.\" indicating a wild reference. 143.\" ``code'' (hex) is the concatenation of the 144.\" MMU 145.\" status register 146.\" (see <hp300/cpu.h>) 147.\" in the high 16 bits and the 68020 special status word 148.\" (see the 68020 manual, page 6-17) 149.\" in the low 16. 150.\" ``v'' (hex) is the virtual address which caused the fault. 151.\" Additionally, the kernel will dump about a screenful of semi-useful 152.\" information. 153.\" ``pid'' (decimal) is the process id of the process running at the 154.\" time of the exception. 155.\" Note that if we panic in an interrupt routine, 156.\" this process may not be related to the panic. 157.\" ``ps'' (hex) is the 68020 processor status register ``ps''. 158.\" ``pc'' (hex) is the value of the program counter saved 159.\" on the hardware exception frame. 160.\" It may 161.\" .Em not 162.\" be the PC of the instruction causing the fault. 163.\" ``sfc'' and ``dfc'' (hex) are the 68020 source/destination function codes. 164.\" They should always be one. 165.\" ``p0'' and ``p1'' are the 166.\" VAX-like 167.\" region registers. 168.\" They are of the form: 169.\" .Pp 170.\" .Bd -ragged -offset indent 171.\" <length> '@' <kernel VA> 172.\" .Ed 173.\" .Pp 174.\" where both are in hex. 175.\" Following these values are a dump of the processor registers (hex). 176.\" Finally, is a dump of the stack (user/kernel) at the time of the offense. 177.\" .Pp 178.It Sy "init died (signal #, exit #)" 179The system initialization process has exited with the specified signal number and exit code. This is bad news, as no new 180users will then be able to log in. Rebooting is the only fix, so the 181system just does it right away. 182.El 183.Pp 184That completes the list of panic types you are likely to see. 185.Pp 186If the system has been configured to take crash dumps (see 187.Xr dumpon 8 ) , 188then when it crashes it will write (or at least attempt to write) 189an image of memory into the back end of the dump device, 190usually the same as the primary swap 191area. After the system is rebooted, the program 192.Xr savecore 8 193runs and preserves a copy of this core image and the current 194system in a specified directory for later perusal. See 195.Xr savecore 8 196for details. 197.Pp 198To analyze a dump you should begin by running 199.Xr gdb 1 200with the 201.Fl k 202flag on the system load image and core dump. 203If the core image is the result of a panic, 204the panic message is printed. 205For more details consult the chapter on kernel debugging in 206the 207.Fx 208Developers' Handbook 209.Pq Pa http://www.FreeBSD.org/ . 210.Sh SEE ALSO 211.Xr gdb 1 , 212.Xr dumpon 8 , 213.Xr reboot 8 , 214.Xr savecore 8 215.Sh HISTORY 216A 217.Nm 218man page first appeared in 219.Fx 2.2 . 220