On 08/21/2014 09:07 AM, Robert P. J. Day wrote:
On Thu, 21 Aug 2014, 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...
it seems like you're trying to seek more than a terabyte into that
card.
Well, man says about seek:
seek=N skip N obs-sized blocks at start of output
and obs defaults to 512 bytes, and I *THOUGHT* fdisk was reporting # 512
blocks, not bytes.
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