Shell Programming and Scripting

Objective: To recreate the partitioning setup of /dev/sda on /dev/sdc

How would I parse the below information and initialize variables
(an array?) that can be used to build sgdisk commands in a script, regardless of the number of partitions?

Something along the lines of:

Code:

sgdisk -n $partnum:$startsec:$endsec -t $partnum:$parttype -c $partnum:$name /dev/sdc

for each partition listed in text produced by an sgdisk - i command.

I am thinking that I can save this text to a file in the backup process and then use it in the restoration process...

Thank you vey much in advance for any time and effort expended in answering my
question!

Code:

root@redbrick /: sgdisk -p /dev/sda
Disk /dev/sda: 1465149168 sectors, 698.6 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 3A4C6201-749A-4B13-93E0-A94B52349823
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 1465149134
Partitions will be aligned on 2048-sector boundaries
Total free space is 749229 sectors (365.8 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          411647   200.0 MiB   EF00  EFI System Partition
   2          411648         1435647   500.0 MiB   8300  
   3         1435648      1464401919   697.6 GiB   8300

As this is crucial (and possibly dangerous, e.g. disk structures differ), and as it's a one off exercise, I'd do it manually and not by script/automated parsing.

I agree. This is for a home project on expendable resources. This is part of a Crashed Disk Recovery project that I am working on. Lots of hard disks here to experiment with! 😄

---------- Post updated at 12:15 PM ---------- Previous update was at 12:13 PM ----------

Can you help with the scripting?

Please don't bump posts.

It would take a great deal of trial and error to get what you want. I'm not sure sgdisk -p is printing all the info you really need, and there's often more to it than just plugging in the right numbers.

I take it your goal is to reorganize partitions into some known-good configuration? have you considered dd?

What exactly is your "crashed disk recovery project"?

Yes DD will not work because the cylinders value on the other drive is not the same as the originating drive. so my only approach would be to recreate the partitions manually that match the original drive, format them out, and then replace the file structure in each one of those partitions. In this case it's a single partition for EFI, one for Boot and a LUKS partition... Any other method seems to result in a corrupted partition table.

sgdisk is providing just enough info to recreate the partition structure. I'm just not sure how to pull that info and what "for" loops I would need.

Just how old are these hard drives? "cylinders" is completely meaningless on any drive newer than 1996, and a partition table with primary partition starting at sector 2048 looks pretty modern too.

Having not seen what you were doing, I can't say why your other methods resulted in a corrupted partition table.

The first time I used the DD to copy the first 2048 sectors off the drive and then I used dd to also copy both of the other partitions. At that point gdisk would complain that I had a corrupt GPT table and that my partition was over running X number of sectors into the next partition. I read somewhere that that's because the way that the drive handles writing the information to the disc is based upon the geometry of the cylinders heads and sectors ...

---------- Post updated at 02:22 PM ---------- Previous update was at 02:19 PM ----------

That's why I decided trying to copy the partition information over to another drive was not a good idea and that what I should actually do is just go ahead and zap a disc get a brand new GPT on there and then format it out one partition at a time and then copy the data into it