OT: (a bit) copying WINDOZE (or any other disks)

[Aleksandar Milivojevic]

Laurence Orchard wrote:
>>What's the recommended process to create an exact duplicate (boot sector
>>and all) of a hard drive?  Is it really as simple as:
>>    cat /dev/hda > /dev/hdb
> 
> In answer to the question, I would partition the new drive, 
> then use
> 
> dd if=/dev/<old-drive> of=/dev/<new-drive>

Which would overwrite the partition table, so why bother to partition 
the drive in the first place?

Anyhow, using dd is better solution than using cat.  One dd option to 
check (which might speed up things) is bs=n.  By default it is 512 (one 
disk block), so dd will read 512 bytes at a time.  Using bs=8192 should 
make things faster (this way dd will read/write 16 disk blocks in single 
system call).  Just make sure size of the disk is multiple of whatever 
you use for bs (otherwise you might get error on last read), and that 
argument for bs is multiple of 512 bytes (disk blocks are 512 bytes long).

I'm not sure how happy the system will be if disk geometries are not the 
same (if you simply copy partition table using dd).  Try something along 
the lines "dd if=/dev/hda of=/dev/hdb count=1" (this will copy just the 
MBR, which contains partition table), and than "fdisk /dev/hdb".  See if 
it will complain, and if partition sizes look right.

If not, partition the drive manually, and use dd to copy individual 
partitions instead (dd if=/dev/hda1 of=/dev/hdb1 bs=n)...

Warning: when you copy over MBR (effectively repartitioning the disk), 
the kernel will not be aware of the new partition table.  This is 
because kernel will read it at startup and will chache it.  Quick 
workaround is to do "fdisk /dev/hdb", and exit from it using "w" 
command.  fdisk reads partition table from the disk (not from the 
kernel), and when it writes it out, it calls ioctl that instructs the 
kernel to reread it.  After that, you should be able to test-mount new disk.

-- 
Aleksandar Milivojevic <amilivojevic at pbl.ca>    Pollard Banknote Limited
Systems Administrator                           1499 Buffalo Place
Tel: (204) 474-2323 ext 276                     Winnipeg, MB  R3T 1L7