Re: How to get the size of the loop-device?

[Jari Ruusu <jariruusu@xxxxxxxxxxxxxxxxxxxxx>]

Markus Laire wrote:
> losetup -e AES256 -H random /dev/loop7 "$DEV"
> losetup -e AES256 -H random /dev/loop6 /dev/loop7
> losetup -s $halfsize /dev/loop4 /dev/loop6
> losetup -o $halfsize /dev/loop5 /dev/loop6

You have three loops stacked which does have small run time overhead.
My advise is to stack only two. Something like this:

 losetup -e AES256 -H random /dev/loop7 "$TMPDEV"
 losetup -e AES256 -H random /dev/loop6 "$SWAPDEV"
 losetup -e twofish256 -H random /dev/loop5 /dev/loop7
 losetup -e twofish256 -H random /dev/loop4 /dev/loop6

If do decide to use $halfsize, then you need to make sure that sizelimit
(-s) and offset (-o) options given to losetup must be multiples of 512 bytes.
Just cutting some device size in half does not guarantee that.

-- 
Jari Ruusu  1024R/3A220F51 5B 4B F9 BB D3 3F 52 E9  DB 1D EB E3 24 0E A9 DD

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