FreeBSD drops to single user mode

[Paul Schmehl]

Recently I experienced something that surprised me.  I have a workstation 
with two SATA drives.  The second drive is data only and is mounted r/w 
when the OS boots.  We had a user whose (Windows) computer crashed and they 
wanted to know if we could recover the data.

I said I'd see, and I unplugged the second drive (ad5 on FreeBSD, drive1 on 
Windows) and plugged in the suspect drive, fully expecting to mount it and 
copy files over.  But, when FreeBSD booted, it failed to read ad5 and then 
dropped to single user mode.

I logged in, mounted all my partitions (mount -a) and then tried to mount 
the suspect drive (mount -t ntfs /dev/ad5s2 /mnt/windows).  FreeBSD was 
unable to mount the drive.

I've since made a bit for bit copy of the drive using a forensics program 
and looked at the drive, and it is definitely FUBAR.

My question is, why did FBSD drop to single user mode instead of completely 
the boot process?

Here's my fstab, if that illuminates anything:

# Device                Mountpoint      FStype  Options         Dump 
Pass#
/dev/ad4s2b             none            swap    sw              0       0
/dev/ad4s2a             /               ufs     rw              1       1
/dev/ad4s2d             /tmp            ufs     rw              2       2
/dev/ad4s2f             /usr            ufs     rw              2       2
/dev/ad4s2e             /var            ufs     rw              2       2
/dev/ad5s1d             /files          ufs     rw              2       2
/dev/acd0               /cdrom          cd9660  ro,noauto       0       0
/dev/acd1               /cdrom1         cd9660  ro,noauto       0       0
linprocfs       /compat/linux/proc   linprocfs  rw              0       0

Paul Schmehl (pauls at utdallas.edu)
Adjunct Information Security Officer
University of Texas at Dallas
AVIEN Founding Member
http://www.utdallas.edu/ir/security/