Using 'dd' to make a backup of an openwrt image (that has been
installed and configured) on a 64MB CF card
# dd if=/dev/sdb of=openwrt.10.03.1_alix_installation.backup.img bs=4K
dd: reading `/dev/sdb': Input/output error
<<<<< this line says I/O error!
15648+0 records in
15648+0 records out
64094208 bytes (64 MB) copied, 68.722 s, 933 kB/s
but the copy is done but with return code = 1
# ls -l openwrt.10.03.1_alix_installation.backup.img
-rw-r--r-- 1 root root 64094208 May 27 16:49
openwrt.10.03.1_alix_installation.backup.img
This shows it indeed copied over 64MB into the backup image file.
# file -s openwrt.10.03.1_alix_installation.backup.img
openwrt.10.03.1_alix_installation.backup.img: x86 boot sector; GRand
Unified Bootloader, stage1 version 0x3, stage2 address 0x2000, stage2
segment 0x200; partition 1: ID=0x83, active, starthead 1, startsector
63, 28609 sectors; partition 2: ID=0x83, starthead 7, startsector
28672, 96513 sectors, code offset 0x48
This shows that indeed the file is a hard disk image with two
partitions in it with GRUB as the boot loader.
# fdisk -l openwrt.10.03.1_alix_installation.backup.img
Disk openwrt.10.03.1_alix_installation.backup.img: 64 MB, 64094208 bytes
255 heads, 63 sectors/track, 7 cylinders, total 125184 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
Disk identifier: 0x00074710
Device Boot Start
End Blocks Id System
openwrt.10.03.1_alix_installation.backup.img1 * 63
28671 14304+ 83 Linux
openwrt.10.03.1_alix_installation.backup.img2 28672
125184 48256+ 83 Linux
fdisk also recognizes the file as a hard disk image with two partitions.
If there were i/o errors with the CF card then I think there would
have been errors reported by the above tools.
Any hypothesis for this anamoly?
--
Arun Khan
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