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newsEasyDD now verifies write
Myself and a couple of other people have had issues with faulty
USB Flash drives. This is an insidious problem, failing bits may go
unnoticed, just causing damage. Or it could be noticed, even causing
failure to boot.
I have proposed two ways to tackling this. Firstly, EasyDD can be
enhanced to verify a write. Secondly, some checksums can be performed at
bootup.
I have implemented the first one. EasyDD is a utility in EasyOS, CLI
or GUI, for writing an image file to a drive. An explanation of EasyDD
is here:
https://easyos.org/install/how-to-write-easyos-to-a-flash-drive.html
Verification is implemented in two steps. Firstly, the image file is
written to the Flash drive with all bits flipped (inverted). It is then
read back to verify.
Then, the normal image file is written to the drive, and read back to verify.
This verifies that the bits are functioning, able to flip to 1 or 0,
as well as verifies that the image file has been written successfully.
Inverting the image file is an interesting exercise. It has to be
done in a pipeline, between uncompressing of the image file, and writing
to the drive. There is a method using the 'tr' utility, as described
here:
...which is very slow. A C utility to do it is here:
I have named this utility 'bitflip' and it will be in the next release of EasyOS. The 'easydd' utility checks for existence of 'bitlfip' and if not existing, uses 'tr'.
I have uploaded the latest easydd here:
http://bkhome.org/files/easydd.gz
...it lives at /usr/sbin, and will need to have it's executable permissions set after uncompressing. You will find it to be a bit slow without the 'bitflip' utility.
EDIT 2020-06-16:
EasyDD has been considerably enhanced since first created, and there is an introduction page, with download link:
Tags: easy