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. Neither the name of the University nor the names of its contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.\" $FreeBSD$ 34.\" 35.Dd July 23, 2011 36.Dt CRASH 8 37.Os 38.Sh NAME 39.Nm crash 40.Nd FreeBSD system failures 41.Sh DESCRIPTION 42This section explains a bit about system crashes 43and (very briefly) how to analyze crash dumps. 44.Pp 45When the system crashes voluntarily it prints a message of the form 46.Bl -diag -offset indent 47.It "panic: why i gave up the ghost" 48.El 49.Pp 50on the console, and if dumps have been enabled (see 51.Xr dumpon 8 ) , 52takes a dump on a mass storage peripheral, 53and then invokes an automatic reboot procedure as 54described in 55.Xr reboot 8 . 56Unless some unexpected inconsistency is encountered in the state 57of the file systems due to hardware or software failure, the system 58will then resume multi-user operations. 59.Pp 60The system has a large number of internal consistency checks; if one 61of these fails, then it will panic with a very short message indicating 62which one failed. 63In many instances, this will be the name of the routine which detected 64the error, or a two-word description of the inconsistency. 65A full understanding of most panic messages requires perusal of the 66source code for the system. 67.Pp 68The most common cause of system failures is hardware failure, which 69can reflect itself in different ways. 70Here are the messages which 71are most likely, with some hints as to causes. 72Left unstated in all cases is the possibility that hardware or software 73error produced the message in some unexpected way. 74.Pp 75.Bl -diag -compact 76.It "cannot mount root" 77This panic message results from a failure to mount the root file system 78during the bootstrap process. 79Either the root file system has been corrupted, 80or the system is attempting to use the wrong device as root file system. 81Usually, an alternate copy of the system binary or an alternate root 82file system can be used to bring up the system to investigate. 83Most often 84this is done by the use of the boot floppy you used to install the system, 85and then using the 86.Dq fixit 87floppy. 88.Pp 89.It "init: not found" 90This is not a panic message, as reboots are likely to be futile. 91Late in the bootstrap procedure, the system was unable to locate 92and execute the initialization process, 93.Xr init 8 . 94The root file system is incorrect or has been corrupted, or the mode 95or type of 96.Pa /sbin/init 97forbids execution or is totally missing. 98.Pp 99.It "ffs_realloccg: bad optim" 100.It "ffs_valloc: dup alloc" 101.It "ffs_alloccgblk: cyl groups corrupted" 102.It "ffs_alloccg: map corrupted" 103.It "blkfree: freeing free block" 104.It "blkfree: freeing free frag" 105.It "ifree: freeing free inode" 106These panic messages are among those that may be produced 107when file system inconsistencies are detected. 108The problem generally results from a failure to repair damaged file systems 109after a crash, hardware failures, or other condition that should not 110normally occur. 111A file system check will normally correct the problem. 112.Pp 113.It "timeout table full" 114This really should not be a panic, but until the data structure 115involved is made to be extensible, running out of entries causes a crash. 116If this happens, make the timeout table bigger. 117.Pp 118.\" .It "trap type %d, code = %x, v = %x" 119.\" An unexpected trap has occurred within the system; the trap types are: 120.\" .Bl -column xxxx -offset indent 121.\" 0 bus error 122.\" 1 address error 123.\" 2 illegal instruction 124.\" 3 divide by zero 125.\" .No 4\t Em chk No instruction 126.\" .No 5\t Em trapv No instruction 127.\" 6 privileged instruction 128.\" 7 trace trap 129.\" 8 MMU fault 130.\" 9 simulated software interrupt 131.\" 10 format error 132.\" 11 FP coprocessor fault 133.\" 12 coprocessor fault 134.\" 13 simulated AST 135.\" .El 136.\" .Pp 137.\" The favorite trap type in system crashes is trap type 8, 138.\" indicating a wild reference. 139.\" ``code'' (hex) is the concatenation of the 140.\" MMU 141.\" status register 142.\" (see <hp300/cpu.h>) 143.\" in the high 16 bits and the 68020 special status word 144.\" (see the 68020 manual, page 6-17) 145.\" in the low 16. 146.\" ``v'' (hex) is the virtual address which caused the fault. 147.\" Additionally, the kernel will dump about a screenful of semi-useful 148.\" information. 149.\" ``pid'' (decimal) is the process id of the process running at the 150.\" time of the exception. 151.\" Note that if we panic in an interrupt routine, 152.\" this process may not be related to the panic. 153.\" ``ps'' (hex) is the 68020 processor status register ``ps''. 154.\" ``pc'' (hex) is the value of the program counter saved 155.\" on the hardware exception frame. 156.\" It may 157.\" .Em not 158.\" be the PC of the instruction causing the fault. 159.\" ``sfc'' and ``dfc'' (hex) are the 68020 source/destination function codes. 160.\" They should always be one. 161.\" ``p0'' and ``p1'' are the 162.\" VAX-like 163.\" region registers. 164.\" They are of the form: 165.\" .Pp 166.\" .Bd -ragged -offset indent 167.\" <length> '@' <kernel VA> 168.\" .Ed 169.\" .Pp 170.\" where both are in hex. 171.\" Following these values are a dump of the processor registers (hex). 172.\" Finally, is a dump of the stack (user/kernel) at the time of the offense. 173.\" .Pp 174.It "init died (signal #, exit #)" 175The system initialization process has exited with the specified 176signal number and exit code. 177This is bad news, as no new users will then be able to log in. 178Rebooting is the only fix, so the 179system just does it right away. 180.El 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. 190After the system is rebooted, the program 191.Xr savecore 8 192runs and preserves a copy of this core image and the current 193system in a specified directory for later perusal. 194See 195.Xr savecore 8 196for details. 197.Pp 198To analyze a dump you should begin by running 199.Xr kgdb 1 200on 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.%B "FreeBSD Developers' Handbook" 206.Pq Pa https://www.freebsd.org/doc/en/books/developers-handbook/ . 207.Sh SEE ALSO 208.Xr kgdb 1 , 209.Xr dumpon 8 , 210.Xr reboot 8 , 211.Xr savecore 8 212.Sh HISTORY 213The 214.Nm 215manual page first appeared in 216.Fx 2.2 . 217