this post was submitted on 29 Jan 2024
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We'll dunno much but wouldn't the UUID of the drive partition change?
If you resize the partition? No, the UUID gets allocated when the partition is created and stays the same for the lifetime of the partition. It only changes if you explicitly change it manually. Which is something that's only needed very rarely.
For example I had to do it when I migrated my root disk to a larger SSD by
cat-ing the entire disk to the new one and I wanted to keep both connected for a while (so I can boot into the old one in case anything went wrong). I had to change the UUID of the partition on the new disk but I still ran into some obscure grub issues and had to boot a system rescue live stick into the new disk to update grub properly. Overall it's not a very good idea, in the future I think I'll stick torsync -avxroot into the new partition.Wait you can cat an entire device to another like that? I’ve always been told to use dd
You can even use
cpof I recall correctly,ddallows to tune some parameters but it's not strictly necessary.You can, it will copy until it runs out of source or runs out of destination so it's very simple to use for stuff like this. Performance also tends to be very good because it chooses some good defaults for block size and so on, unlike dd where you have to choose by hand.
dd also has some issues that you have to be aware of such as the fact it will always fill full blocks by default. For example if you choose 1M blocks and your source is 1.5M it will write 2M. It's not a problem in a scenario like I described where the new disk is larger and empty and that extra 0.5M will go unnoticed, but if you had some other partition past the 1.5M mark it may potentially mess it up. You have to use a flag to make it write exactly what it reads ("fullblock" I think – yeah that's intuitive; unless they changed it and now it's reversed by default? I don't even know).
So yeah overall dd is more trouble than it's worth unless you're prepared and need to control the copy super-exactly.