On 11/22/20 12:08 PM, Sreyan Chakravarty wrote:
I would like to know how can I clone this logical volume to my external
hard disk.
I have seen commands like :
dd if=/dev/vg/root_lv of=/mnt/exthdd bs=64k conv=noerror,sync
status=progress
I have a couple of questions about this:
1) Why use noerror and sync?
noerror might give me a corrupted image and sync is just going to
increase the size of my image with padding.
>
> Why use them?
I don't know where you got that command from, but "noerror" would
generally be used if the source device is failing. And yes, in that
case, you might get a corrupted image. I think "sync" is related to
that. If there's an error, you might get a short read, so "sync" makes
sure a full block is written. Otherwise, the copied filesystem would be
completely messed up.
2) What is rationale behind block size?
Will using 4M block size instead of 64K give me a different image? I
need my image to be an EXACT COPY.
The block size won't change the resulting image. It's just that the
default block size of 512 bytes can be quite inefficient. Using a
larger block reduces the CPU time used in system calls.
But as Jorge said, this is probably not the right tool for what you want
to do.
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