# VyOS 1.3.x image upgrade scipt checked if an image file was a valid ISO file
# by grepping it for "ISO9660".
# (The correct way to do that would be to use file/libmagic,
#  but we cannot change the past).
# At some point something has changed in xorriso or some other tool
# and images no longer include that string.
# so the image validity check fails.
# To allow direct upgrades from older versions,
# we artificially include that string to make the old check pass.
ISO9660