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.\" $Id: crash.8,v 1.6 1997/02/22 13:26:18 peter Exp $ 38.\" 39.Dd February 2, 1996 40.Dt CRASH 8 i386 41.Os FreeBSD 42.Sh NAME 43.Nm crash 44.Nd 45.Tn FreeBSD 46system failures 47.Sh DESCRIPTION 48This section explains a bit about system crashes 49and (very briefly) how to analyze crash dumps. 50.Pp 51When the system crashes voluntarily it prints a message of the form 52.Bd -ragged -offset indent 53panic: why i gave up the ghost 54.Ed 55.Pp 56on the console, and if dumps have been enabled (see 57.Xr dumpon 8 ) , 58takes a dump on a mass storage peripheral, 59and then invokes an automatic reboot procedure as 60described in 61.Xr reboot 8 . 62Unless some unexpected inconsistency is encountered in the state 63of the file systems due to hardware or software failure, the system 64will then resume multi-user operations. 65.Pp 66The system has a large number of internal consistency checks; if one 67of these fails, then it will panic with a very short message indicating 68which one failed. 69In many instances, this will be the name of the routine which detected 70the error, or a two-word description of the inconsistency. 71A full understanding of most panic messages requires perusal of the 72source code for the system. 73.Pp 74The most common cause of system failures is hardware failure, which 75can reflect itself in different ways. Here are the messages which 76are most likely, with some hints as to causes. 77Left unstated in all cases is the possibility that hardware or software 78error produced the message in some unexpected way. 79.Pp 80.Bl -tag -width Ds -compact 81.It Sy "cannot mount root" 82This panic message results from a failure to mount the root filesystem 83during the bootstrap process. 84Either the root filesystem has been corrupted, 85or the system is attempting to use the wrong device as root filesystem. 86Usually, an alternate copy of the system binary or an alternate root 87filesystem can be used to bring up the system to investigate. Most often 88this is done by the use of the boot floppy you used to install the system, 89and then using the "fixit" floppy. 90.Pp 91.It Sy "init: not found" 92This is not a panic message, as reboots are likely to be futile. 93Late in the bootstrap procedure, the system was unable to locate 94and execute the initialization process, 95.Xr init 8 . 96The root filesystem is incorrect or has been corrupted, or the mode 97or type of 98.Pa /sbin/init 99forbids execution or is totally missing. 100.Pp 101.Pp 102.It Sy "ffs_realloccg: bad optim" 103.It Sy "ffs_valloc: dup alloc" 104.It Sy "ffs_alloccgblk: cyl groups corrupted" 105.It Sy "ffs_alloccg: map corrupted" 106.It Sy "blkfree: freeing free block" 107.It Sy "blkfree: freeing free frag" 108.It Sy "ifree: freeing free inode" 109These panic messages are among those that may be produced 110when filesystem inconsistencies are detected. 111The problem generally results from a failure to repair damaged filesystems 112after a crash, hardware failures, or other condition that should not 113normally occur. 114A filesystem check will normally correct the problem. 115.Pp 116.It Sy "timeout table full" 117This really shouldn't be a panic, but until the data structure 118involved is made to be extensible, running out of entries causes a crash. 119If this happens, make the timeout table bigger. 120.Pp 121.\" .It Sy "trap type %d, code = %x, v = %x" 122.\" An unexpected trap has occurred within the system; the trap types are: 123.\" .Bl -column xxxx -offset indent 124.\" 0 bus error 125.\" 1 address error 126.\" 2 illegal instruction 127.\" 3 divide by zero 128.\" .No 4\t Em chk No instruction 129.\" .No 5\t Em trapv No instruction 130.\" 6 privileged instruction 131.\" 7 trace trap 132.\" 8 MMU fault 133.\" 9 simulated software interrupt 134.\" 10 format error 135.\" 11 FP coprocessor fault 136.\" 12 coprocessor fault 137.\" 13 simulated AST 138.\" .El 139.\" .Pp 140.\" The favorite trap type in system crashes is trap type 8, 141.\" indicating a wild reference. 142.\" ``code'' (hex) is the concatenation of the 143.\" MMU 144.\" status register 145.\" (see <hp300/cpu.h>) 146.\" in the high 16 bits and the 68020 special status word 147.\" (see the 68020 manual, page 6-17) 148.\" in the low 16. 149.\" ``v'' (hex) is the virtual address which caused the fault. 150.\" Additionally, the kernel will dump about a screenful of semi-useful 151.\" information. 152.\" ``pid'' (decimal) is the process id of the process running at the 153.\" time of the exception. 154.\" Note that if we panic in an interrupt routine, 155.\" this process may not be related to the panic. 156.\" ``ps'' (hex) is the 68020 processor status register ``ps''. 157.\" ``pc'' (hex) is the value of the program counter saved 158.\" on the hardware exception frame. 159.\" It may 160.\" .Em not 161.\" be the PC of the instruction causing the fault. 162.\" ``sfc'' and ``dfc'' (hex) are the 68020 source/destination function codes. 163.\" They should always be one. 164.\" ``p0'' and ``p1'' are the 165.\" VAX-like 166.\" region registers. 167.\" They are of the form: 168.\" .Pp 169.\" .Bd -ragged -offset indent 170.\" <length> '@' <kernel VA> 171.\" .Ed 172.\" .Pp 173.\" where both are in hex. 174.\" Following these values are a dump of the processor registers (hex). 175.\" Finally, is a dump of the stack (user/kernel) at the time of the offense. 176.\" .Pp 177.It Sy "init died (signal #, exit #)" 178The system initialization process has exited with the specified signal number and exit code. This is bad news, as no new 179users will then be able to log in. Rebooting is the only fix, so the 180system just does it right away. 181.Pp 182That completes the list of panic types you are likely to see. 183.Pp 184If the system has been configured to take crash dumps (see 185.Xr dumpon 8 ) , 186then when it crashes it will write (or at least attempt to write) 187an image of memory into the back end of the dump device, 188usually the same as the primary swap 189area. After the system is rebooted, the program 190.Xr savecore 8 191runs and preserves a copy of this core image and the current 192system in a specified directory for later perusal. See 193.Xr savecore 8 194for details. 195.Pp 196To analyze a dump you should begin by running 197.Xr gdb 1 198with the 199.Fl k 200flag on the system load image and core dump. 201If the core image is the result of a panic, 202the panic message is printed. 203For more details consult the chapter on kernel debugging in 204the 205.Tn FreeBSD 206handbook (http://www.freebsd.org). 207.Sh SEE ALSO 208.Xr gdb 1 , 209.Xr dumpon 8 , 210.Xr reboot 8 , 211.Xr savecore 8 212.Sh HISTORY 213A 214.Nm crash 215man page first appeared in 216.Fx 2.2 . 217