this post was submitted on 29 Jan 2024
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Wait you can cat an entire device to another like that? I’ve always been told to use dd
You can even use
cp
of I recall correctly,dd
allows 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.