mount problem after the kernel load: Manual root filesystem specification

[Olivier Utkala]

Hi All,

After the kernel load, it's necessary for me to enter the folowing to 
continue the start process:
mountroot> ufs:ad2s1a

I find on another machine, wich start correctly, with the same version of 
FreeBSD, that the last line of command kenv results:
    vfs.root.mountfrom="ufs:/dev/ad0s1a"
On my start-problem machine, these last line don't exists.

How can I resolve these problem to start correctly, without enter filesystem 
specification each time?
Thanks in advance for any response.

dmesg command results:

================8<--------------------------------------------------------------
Copyright (c) 1992-2007 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
        The Regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 6.2-RELEASE-p4 #0: Thu Apr 26 17:40:53 UTC 2007
    root at i386-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: VIA C3 Samuel 2 (601.37-MHz 686-class CPU)
  Origin = "CentaurHauls"  Id = 0x673  Stepping = 3
  Features=0x803035<FPU,DE,TSC,MSR,MTRR,PGE,MMX>
real memory  = 469696512 (447 MB)
avail memory = 450170880 (429 MB)



vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
ums0: Cypress Sem PS2/USB Browser Combo Mouse, rev 1.00/0.00, addr 2, iclass
3/1
ums0: 5 buttons and Z dir.
Timecounter "TSC" frequency 601368219 Hz quality 800
Timecounters tick every 1.000 msec
acd0: CDROM <BCD E520C/0.40> at ata0-slave UDMA33
ad2: 157066MB <HDT722516DLAT80 V43OA96A> at ata1-master UDMA133

Manual root filesystem specification:
  <fstype>:<device>  Mount <device> using filesystem <fstype>
                       eg. ufs:da0s1a
  ?                  List valid disk boot devices
  <empty line>       Abort manual input

mountroot> ufs:ad2s1a
Trying to mount root from ufs:ad2s1a
================8<--------------------------------------------------------------

-------------------
Olivier Utkala