Can i dd if=/dev/sdb of=/dev/sdc if hdsize(sdb)>hdsize(sdc) & size(sdb)<hdsize(sdc) ?

ununun · 06-27-2011, 09:38 AM

Code:

$parted -l
Model: Generic Flash Disk (scsi)
Disk /dev/sdb: 4216MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  4215MB  4214MB  primary  ext4         boot


Model: USBModem Disk (scsi)
Disk /dev/sdc: 3964MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      4194kB  3964MB  3959MB  primary

sdb1 is my current linux system.

i want to make exact bootable copy of sdb to sdc.

would
dd if=/dev/sdb of=/dev/sdc
do that ?

the actual size of sdb (which is hdsize(sdb) - free space(sdb)) is less than hdsize(sdc).

dimm0k · 06-27-2011, 09:58 AM

Your best bet would be to resize sdb1 to match the size of sdc1 and then use dd. This is because dd will copy the disk sector by sector and there's a possibility there could be data at the end of sdb1 that would be truncated when it reaches the end of sdc.

ununun · 06-27-2011, 10:17 AM

Quote:

Originally Posted by dimm0k

Your best bet would be to resize sdb1 to match the size of sdc1 and then use dd. This is because dd will copy the disk sector by sector and there's a possibility there could be data at the end of sdb1 that would be truncated when it reaches the end of sdc.

i think to resize sdb1 (root partition) i have to boot from other linux. and thats what i was hoping to avoid.

Karl Godt · 06-27-2011, 02:46 PM

Why don't you simple use the rsync command and copy it simply . This works for me to restore an accidentially wiped partition .

dimm0k · 06-27-2011, 11:18 PM

Quote:

Originally Posted by ununun

i think to resize sdb1 (root partition) i have to boot from other linux. and thats what i was hoping to avoid.

You are correct... if you want to resize the root partition, you cannot have it mounted so your two options would be to either get a "live" distro that contains gparted, boot off of the CD and resize from there. At the same time, you can dd while there as well. I use SystemRescueCD and PartedMagic from time to time for such operations. Your second option would be what Karl Godt mentioned and that is to use rsync to copy the files over from one drive to the other. This second option of course means you can do it without getting another distro and without needing to reboot.

ununun · 06-27-2011, 11:36 PM

i dont think rsync can clone MBR.

i am going with resize and dd.

i will let you know the result soon.

thanks for all help.

Karl Godt · 06-28-2011, 11:48 AM

You possible may copy the mbr with

Code:

dd if=/dev/sda of=/dev/sdb bs=512 count=1

And to check :

Code:

 dd if=/dev/sdb of=/MBRsdb bs=512 count=1

and

Code:

file /MBRsdb

should look like
/MBRsdb: x86 boot sector;
partition 2: ID=0xf, starthead 254, startsector 71312535, 905455530 sectors;
partition 3: ID=0x83, starthead 254, startsector 20755980, 20627460 sectors;
partition 4: ID=0x83, starthead 254, startsector 41383440, 29929095 sectors, code offset 0x5e

The output above is done using grub4dos-V0.4.4 . Why partition 1 is missing I don't know .
Grub4dos is installed to partition 1 . Works ok for me .