On 08/21/2014 07:51 AM, Robert Moskowitz wrote:
More on my compressing images from SDcards.
I only need the boot info and 1st partition, so I remove the other
partitions, but of course there is still 1s out there so it will not
compress efficiently. I want to zero out the end of the card so first
I use fdisk:
# fdisk -l /dev/sdb
Disk /dev/sdb: 7.4 GiB, 7969177600 bytes, 15564800 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x0009e2ad
Device Boot Start End Blocks Id System
/dev/sdb1 8192 1007615 499712 83 Linux
Then dd:
# dd if=/dev/zero of=/dev/sdb bs=1M seek=1007620
dd: ‘/dev/sdb’: cannot seek: Invalid argument
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000652852 s, 0.0 kB/s
======================
seems you cannot seek on an SDcard. How do I do this? Since the change
in partition 1 is trivial, if I have to start again from an SDcard
with all 3 paritions, I can do that...
I'd create a new partition on the remainder of the card, and then dd
/dev/zero to that partition. I don't know squat about the bits and
pieces of partition structure but that should wipe most of it at least.
--
Stephen Berg
Systems Administrator
NRL Code: 7320
Office: 228-688-5738
stephen.berg.ctr@xxxxxxxxxxxxxxx
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