I reported:

>>   disklabel: Invalid signature in mbr record 0
>>   write: Read-only file system

Lubomir Sedlacik <salo@Xtrmntr.org> suggests:

> the disklabels of the underlying device and cgd0 probably overlap.
> you need to move the cgd0 one a bit inside the volume.

Description of system is below my signature as output from commands.
Summary:

   wd0 and wd1 have BIOS partition 0 occupying full disk (starting at 63)
   wd0f + wd1f (each at offset 8193087) are type RAID, together form "raid0"
   raid0 has BIOS partition 0 occupying full device (starting at 63)
   raid0e (also starting at 63) is type ccd, and contains cgd0.
   cgd0 has BIOS partition 0 occupying full device (starting at 63)
   cgd0e (also starting at 63) is type 4.2BSD

In this case the underlying device is raid0, whose disklabel is... where?
At block 63 of raid0?  But if so, how come my writing a BIOS label
onto the cgd (raid0e, also at block 63 of raid0) doesn't trash the
raid0 disklabel?  Call me confused. :-(

If I understand your suggestion correctly, you recommend that I move
raid0e forward a bit to clear the raid0 disklabel so that the cgd on
raid0e won't stomp on it?  How big is the disklabel?


Anne.
-- 
Ms. Anne Bennett, Senior Sysadmin, ENCS, Concordia University, Montreal H3G 1M8
anne@encs.concordia.ca                                    +1 514 848-2424 x2285
-------------------------------------------------------------------------------
# disklabel wd0

type: unknown
disk: SAMSUNG SP2504C
[...]
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:   1024128        63     4.2BSD   1024  8192 46552  # (Cyl.      0*-   1016*)
 b:   6144768   1024191       swap                     # (Cyl.   1016*-   7112*)
 c: 488397105        63     unused      0     0        # (Cyl.      0*- 484520)
 d: 488397168         0     unused      0     0        # (Cyl.      0 - 484520)
 e:   1024128   7168959     4.2BSD   1024  8192 46552  # (Cyl.   7112*-   8128*)
 f: 480204081   8193087       RAID                     # (Cyl.   8128*- 484520)

# disklabel wd1
type: unknown
disk: ST3250620AS    
[...]
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:   1024128        63     4.2BSD   1024  8192 46552  # (Cyl.      0*-   1016*)
 b:   6144768   1024191       swap                     # (Cyl.   1016*-   7112*)
 c: 488397105        63     unused      0     0        # (Cyl.      0*- 484520)
 d: 488397168         0     unused      0     0        # (Cyl.      0 - 484520)
 e:   1024128   7168959     4.2BSD   1024  8192 46552  # (Cyl.   7112*-   8128*)
 f: 480204081   8193087       RAID                     # (Cyl.   8128*- 484520)

# quill# raidctl -s raid0
Components:
           /dev/wd0f: optimal
           /dev/wd1f: optimal
No spares.
[...]Parity status: clean
Reconstruction is 100% complete.
Parity Re-write is 100% complete.
Copyback is 100% complete.

# disklabel raid0

type: RAID
disk: raid
label: raid0
[...]
#        size    offset     fstype [fsize bsize cpg/sgs]
 c: 480203953        63     unused      0     0        # (Cyl.      0*- 3751593*)
 d: 480204016         0     unused      0     0        # (Cyl.      0 - 3751593*)
 e:  10485760        63        ccd                     # (Cyl.      0*-  81920*)
 f: 469718193  10485823     4.2BSD   4096 32768 58336  # (Cyl.  81920*- 3751593*)

# cat /etc/cgd/cgd.conf
# cgd  target       [paramsfile]
cgd0   /dev/raid0e

# fdisk cgd0
Disk: /dev/rcgd0d
[...]
Partition table:
0: NetBSD (sysid 169)
    start 63, size 10485697 (5120 MB, Cyls 0-652/180/41)
1: <UNUSED>
2: <UNUSED>
3: <UNUSED>
Bootselector disabled.

# disklabel cgd0
type: cgd
disk: cgd
label: cgd0
[...]
#        size    offset     fstype [fsize bsize cpg/sgs]
 c:  10485697        63     unused      0     0        # (Cyl.      0*-   5119)
 d:  10485760         0     unused      0     0        # (Cyl.      0 -   5119)
 e:  10485697        63     4.2BSD      0     0     0  # (Cyl.      0*-   5119)

-------------------------------------------------------------------------------