The fix for bug 1871397 creates a private interface requirement between one of the default NSS plugins and libc. This means that a long-running process, like systemd, may be loaded with the old libc.so.6, but not yet have accessed any IdM information via NSS plugins. When a service is forked the service using USER= tried to load the newly upgraded NSS plugin, and that fails because it needs the new GLIBC_PRIVATE API from libc.so.6. Even though glibc is marked as needing a reboot after upgrade, we want to, and can achieve a satisfactory result by duplicating the GLIBC_PRIVATE function into the NSS plugin itself (at least we can in this case). If we can, we should attempt to allow an upgrade without requiring a reboot since this supports kpatch and avoids server reboots. In-place upgrades from RHEL7 to RHEL8 should not be impacted because they would reboot the system and run from an initramfs that modifies the existing install and then reboots.
This was initially reported by CentOS 8 Stream users here: https://bugzilla.redhat.com/show_bug.cgi?id=1871397#c14
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (Moderate: glibc security, bug fix, and enhancement update), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHSA-2021:1585