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Why does the verification of hash value calculated on a file placed in tmp dir fail?

Question asked by Alex Geng on May 5, 2020
Latest reply on May 7, 2020 by Yuri Muhin



We observe a phenomenon on a custom board that is equipped with an i.mx7d and 512MB lpddr2.

The verification of the hash value calculated on a file placed in tmp directory fails:
# dd if=/dev/urandom of=/tmp/testfile bs=1M count=50
50+0 records in
50+0 records out
# md5sum /tmp/testfile > /tmp/testmd5
# md5sum -c /tmp/testmd5
/tmp/testfile: FAILED
md5sum: WARNING: 1 of 1 computed checksums did NOT match
On the other hand a standard linux memory test succeeds on the same board:
# memtester 200 1
memtester version 4.3.0 (32-bit)
Copyright (C) 2001-2012 Charles Cazabon.
Licensed under the GNU General Public License version 2 (only).

pagesize is 4096
pagesizemask is 0xfffff000
want 200MB (209715200 bytes)
got  200MB (209715200 bytes), trying mlock ...locked.
Loop 1/1:
  Stuck Address       : ok
  Random Value        : ok
  Compare XOR         : ok
  Compare SUB         : ok
  Compare MUL         : ok
  Compare DIV         : ok
  Compare OR          : ok
  Compare AND         : ok
  Sequential Increment: ok
  Solid Bits          : ok
  Block Sequential    : ok
  Checkerboard        : ok
  Bit Spread          : ok
  Bit Flip            : ok
  Walking Ones        : ok
  Walking Zeroes      : ok
  8-bit Writes        : ok
  16-bit Writes       : ok



What could be the reason for this behavior?


Thanks and best regards