nbdkit is our super-flexible, pluggable NBD server. Read more about it here:
https://github.com/libguestfs/nbdkit https://rwmj.wordpress.com/?s=nbdkit
This package is in EPEL, and was added to RHEL 7.6.
Now unfortunately (owing to my screw up) we added a lower NVR to RHEL 7.6 than is present in EPEL. If we remove nbdkit from EPEL then there wouldn't be an upgrade path to RHEL 7.6. This in itself wouldn't matter since the version numbers are similar except for a second screw up (yes, it's me again). The RHEL 7.6 package backports a substantial feature from upstream. The EPEL package had a higher NVR and fewer features. Lack of the new feature will break virt-v2v and the ability to read virtual machines from VMware.
To get around that as the last release in EPEL I backported all the changes from RHEL 7.6:
https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2018-093ee2a8e8 https://src.fedoraproject.org/rpms/nbdkit/c/c59e48e5bb7b8867b4c180bf86d5243b...
This EPEL package still has a higher NVR than RHEL 7.6, but this time it truly doesn't matter because the packages are "effectively" the same. If you're going from (eg) CentOS 7.5 + EPEL -> 7.6, you won't get the nbdkit package from CentOS 7.6 (because lower NVR) but you will still have all the features, provided you got the final EPEL nbdkit package.
I hope that rather long explanation is clear!
I think there are two things that need to happen as a result:
(1) We need to make sure nbdkit-1.2.7-2.el7 from EPEL 7 goes out to all the mirrors, and then wait a little while for everyone to upgrade to it.
(2) We need to remove nbdkit from EPEL once it has appeared in CentOS and some time has passed for (1) to happen, as per normal procedures when a package is moved from EPEL to RHEL. https://fedoraproject.org/wiki/How_to_remove_a_package_at_end_of_life#EPEL
All of this will be resolved in RHEL 7.7 by an nbdkit package with a higher NVR than all previous.
Rich.