Either command should add 10 bytes to the end of your file. This should mean the MD5 (when next calculated) should be different.
truncate -s +10 <filename>.ext
dd if=/dev/zero bs=1 count=10 >> <yourfile>.<ext>
Either command should add 10 bytes to the end of your file. This should mean the MD5 (when next calculated) should be different.
truncate -s +10 <filename>.ext
dd if=/dev/zero bs=1 count=10 >> <yourfile>.<ext>