The RHEL 7 release brought many changes from RHEL 6, some of them breaking backward compatibility (Systemd, etc). Unfortunately, such changes happened between versions of RHEL 7 too.
Here you will find a non-exhaustive list of such changes.
The RHEL 7.1 release completely changed the way the various NFS services worked.
The nfs-secure-server service doesn’t work the same way anymore, the nfs-idmap service has a new brother, nfs-idmapd, and the Kerberos NFS client gets a new nfs-client.target.
Most of this is not really explained in the official Red Hat documentation!
Hopefully, there is a Kerberos NFS tutorial that took a long time to update!
In RHEL 7.0, you could write:
# nmcli con mod myConn ipv4.addresses "10.0.0.10/24 10.0.0.1"
Since RHEL 7.1, you have to do it in two steps:
# nmcli con mod myConn ipv4.addresses 10.0.0.10/24 # nmcli con mod myConn ipv4.gateway 10.0.0.1
With RHEL 7.2, Systemd moves from v208 to v219. It’s still too early to say if changes breaking backward compatibility happened.
At least one change has already been reported concerning execution of Docker containers. You can read an article on the CentOS blog about Fixing CentOS 7 systemd conflicts with docker.
A new option called RemoveIPC was introduced in RHEL 7.2 through Systemd v219. When set to yes, this option forces a cleanup of all allocated inter-process communication (IPC) resources linked to a user leaving his last session. If a daemon is running as a user with a uid number >=1000, it may crash.
This option should always be set to no by default but, due to the logic of package upgrade, it is highly advisable to set RemoveIPC=no in the /etc/systemd/logind.conf file followed by # systemctl restart systemd-logind (source).
Other Compatibility Problems?
Leave a comment if you find another problem not listed here.