I found that we touch the file /tmp/sysupgrade in a few places --- git grep "tmp/sysupgrade" | grep touch package/base-files/files/sbin/sysupgrade:touch /tmp/sysupgrade package/system/fstools/files/snapshot: touch /tmp/sysupgrade package/system/procd/files/nand.sh: touch /tmp/sysupgrade --- But why ? did not find anything that uses that file.