Assertion (heads < 256) at disk_dos.c:486 in function probe_partition_for_geom(), failed.

[Peter Trenholme]

I noticed that one of my drives was reporting as much free space as 
partitioned space.

The reported geometry for both my 100Gb drives (Both Western Digital 
1000BBs) is 12161/255/63, but hdg reports 100Gb allocated to hdg1, and 
100Gb unallocated whilst hdh (an identical drive) reports a single 
allocated partition of 100Gb.

I was trying to fix the (clearly incorrect) partition information, but 
-- as you see below -- "parted" didn't like what it saw, and backed off.

There's nothing on that drive right now, so I'll see if fdisk can wipe 
all and start over.

Heres your requested information:

address@hidden ~]# fdisk /dev/hdg -l

Disk /dev/hdg: 100.0 GB, 100030242816 bytes
255 heads, 63 sectors/track, 12161 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

  Device Boot      Start         End      Blocks   Id  System
/dev/hdg1               1       12161    97683201    c  W95 FAT32 (LBA)
address@hidden ~]# fdisk /dev/hdg

The number of cylinders for this disk is set to 12161.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
  (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): p

Disk /dev/hdg: 100.0 GB, 100030242816 bytes
255 heads, 63 sectors/track, 12161 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

  Device Boot      Start         End      Blocks   Id  System
/dev/hdg1               1       12161    97683201    c  W95 FAT32 (LBA)

Command (m for help): x

Expert command (m for help): p

Disk /dev/hdg: 255 heads, 63 sectors, 12161 cylinders

Nr AF  Hd Sec  Cyl  Hd Sec  Cyl     Start      Size ID
1 00   1   1    0 254  63  896         63  195366402 0c
2 00   0   0    0   0   0    0          0          0 00
3 00   0   0    0   0   0    0          0          0 00
4 00   0   0    0   0   0    0          0          0 00

The only difference between the above and the otherwise identical output 
for hdh is that the end cylender on hdh is shown as 1022, not 896.  (I 
presume that 896 is incorrect, and will try to change it to 1022.  As I 
said, the drive is currently empty, so I'm feeling free to play around.)

And here's the error message generated by parted:

You found a bug in GNU Parted.  Please email a bug report to 
address@hidden the version (1.6.15), and the following 
message:

Assertion (heads < 256) at disk_dos.c:486 in function 
probe_partition_for_geom() failed.