[Bio-linux-dev] USB-stick checksum failures

[Tony Travis]

Hi, Tim.

We had some problems with the USB-sticks I supplied for the workshop at
AAU in Jorhat recently and I replaced any USB-sticks that failed their
'self-test' (i.e. "Check stick for defects" on the boot menu).

I noticed that they all seemed to fail on the same file, so I
investigated using bio-linux-usb-checker and "md5sum". I tested the
failed' sticks exhaustively using "badblocks" destructive write/read
without any errors and remade them using "bio-linux-usb-maker".

This stick passed its 'self-test' on first boot, but after using it a
few times, it now fails its 'self-test', so I checked it 'live':

> root at biolinux:~# cd /cdrom
> root at biolinux:/cdrom# md5sum --quiet -c md5sum.txt
> ./casper/initrd.lz: FAILED
> md5sum: WARNING: 1 computed checksum did NOT match
> root at biolinux:/cdrom# ls -rtl casper
> total 3455124
> -rwxr-xr-x 1 root root         10 Mar  5 11:30 filesystem.size
> -rwxr-xr-x 1 root root       1063 Mar  5 11:30 filesystem.manifest-remove
> -rwxr-xr-x 1 root root      94031 Mar  5 11:30 filesystem.manifest
> -rwxr-xr-x 1 root root    5815992 Mar  5 12:09 vmlinuz.efi
> -rwxr-xr-x 1 root root 3511578624 Mar  5 12:09 filesystem.squashfs
> -rwxr-xr-x 1 root root   20545577 Mar  7  2015 initrd.lz

It's clear that "initrd.lz" is being written to and it's md5sum will
change. Therefore, the 'self-test' using the original md5sum will always
fail even though there is nothing wrong with the USB-stick.

Some of the USB-sticks were physically bent and not working(!), but I
don't think we had as many USB-stick failures as it seemed because of my
over-zealous rejection of sticks that failed their 'self-test'.

Any idea why "initrd.lz" is being written to?

Bye,

  Tony.

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