Can't unmount oldroot when Apache2 running

[kb2ma]

The attached log files show a failure to unmount the oldroot partition when Apache2 is running on a Beaglebone Black running Debian v9. See the end of stage2.log in the failure case below.

I should say that I assume the problem is Apache. After the failure case, I stopped Apache with systemctl stop apache2, tried again, and it worked. In the success case below, stage1.log also includes a process listing.

Failure

stage1.log
stage2.log
stage2-init.log

Success

stage1.log
stage2.log
stage2-init.log