[svlug] How to back up my son's GPT?

Steve Litt slitt at troubleshooters.com
Wed Nov 26 22:25:48 PST 2014

Hi all,

My son just got a Windows computer, and I want to back up the restore
partition and the GUID Partition Table(s) (GPT) so that, if worst comes
to worst, I can restore his computer to factory condition using the
restore partition.

According to
http://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_table_header_.28LBA_1.29 ,
it would seem that the size to be backed up from the front of /dev/sda
is the number in ((offset 40) - 1), multiplied by the LBA size, which
I think is the sector size. My understanding is that sector size is
usually, but not always, 512 bytes, and I have no idea how to find the
sector size on the disk. Does anyone know?

Once again looking at
http://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_table_header_.28LBA_1.29 ,
it seems that I could back up the secondary partition table by starting
at the LBA identified at ((offset 48) - 1) to the end of /dev/sda1.
Anyone know the proper dd or ddrescue command to go from a certain
offset to the end of the disk, without knowing the length of the amount
to be dd'ed?

By the way, is there a program that already calculates this for me and
maybe even does the dd, or am I going to need to write it?



Steve Litt                *  http://www.troubleshooters.com/
Troubleshooting Training  *  Human Performance

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