Comment # 3 on bug 931049 from Marcus Schaefer

you can disable the runtime check via

   export KIWI_IGNORE_OLD_MOUNTS=1

The buildservice can do that in general when it builds images with kiwi

However the question is still valid why other processes not related to kiwi in
any case have a mount reference to something kiwi mounted and why do these
processes block the owner of the mount to correctly umount it

I'm sorry but in kiwi all I can do is mount and correctly umount once I'm sure
I'm not busy anymore. If some other process or the kernel thinks different
about this I'm lost

We implemented the runtime check to be able to detect the situation but I still
can't tell why this appears.

The link in the initial comment shows a successful build though

If you run parallel image builds in a chroot on the same host the check is
correct and also makes sense. Because that could really cause mount conflicts
and was never supported by kiwi. parallel image builds are only supported
in VMs or containers because they really encapsulated host resources properly
for image builds

If it's not a problem for the buildservice to leave the buildsystem with a busy
proc, sys or some other mount process you can safely export the variable above
which will disable the runtime check

Adding Adrian to CC