FreeBSD 9: fdisk -It crashes kernel

Guy Helmer guy.helmer at
Thu Apr 25 14:15:02 UTC 2013

Encountered a surprise when my disk resizing rc.d script caused FreeBSD 9.1-STABLE to crash. I used "fdisk -It ada0" to determine what the available size of the disk (which happened to be the root disk), and on FreeBSD 9.1 the kernel comes crashing down:

+ fdisk -It ada0
+ /rescue/sed -En 's,.*start ([0-9]+).*size ([0-9]+).*,\1 + \2,p'
vnode_pager_getpages: I/O read error
vm_fault: pager read error, pid 65 (fdisk)
pid 65 (fdisk), uid 0: exited on signal 11
eval: arithmetic expression: expecting primary: ""
Entropy harvesting: point_to_pointeval: date: Device not configured
eval: df: Device not configured
eval: dmesg: Device not configured
cat: /bin/ls: Device not configured
eval: cannot open /etc/fstab: Device not configured
eval: cannot open /etc/fstab: Device not configured
eval: swapon: Device not configured
Warning! No /etc/fstab: skipping disk checks
fstab: /etc/fstab:0: Device not configured

Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address   = 0x0
fault code                     = supervisor read, page not present
instruction pointer      = 0x20:0xc0825fc4
stack pointer               = 0x28:0xc5a088c8
frame pointer              = 0x28:0xc5a08914
code segment            = base 0x0, limit 0xfffff, type 0x1b
                                     = DLP 0, pres 1, def32 1, gran 1
processor eflags       = interrupt enabled, resume, IOPL = 0
current process         = 91 (mount)
[ thread pid 91 tid 100056 ]
Stopped at  g_access+0x24: mlvl 0(%ebx),%eax
db> where
Tracing pid 91 tid 100056 td 0xc84c42f0
g_access(c8481d34,0,1,1,0,…) at g_access+0x24/frame 0xc5a08914
ffs_mount(c8481d34,c0d78380,2,c5a08c00,c829ae6c,…) af ffs_mount+0xf74/frame 0xc5a08a34
vfs_donmount(c84c42f0,10000,0,c84cf200,c84cf200,…) at vfs_donmount+0x1423/frame 0xc5a08c24
sys_nmount(c84c42f0,c5a08ccc,c5a08cc4,1010006,c5a08d08,…) at sys_nmount+0x7f/frame 0xc5a08c48
syscall(c5a08d08) at syscall+0x443/frame 0xc508cfc
Xint0x80_syscall() at Xint0x80_syscall+0x21/frame 0xc5a08cfc
--- syscall (378, FreeBSD ELF32, sys_nmount), eip = 0x480d5feb, esp = 0xbfbfce1c, ebp = 0xbfbfd378 ---

I'll fix my script to not do this, but it seems odd that fdisk -It can make the disk "go away".


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