It seems that latest samba update is not the problem, but actually triggered an unexpected condition:
[root@neth ~]# alternatives --list | grep libwbclient
libwbclient.so.0.14-64 auto /usr/lib64/sssd/modules/libwbclient.so.0.14.0
The sssd library is loaded by winbind instead of the samba one. The sssd library does not work with our setup.
The fix is trivial:
[root@neth ~]# signal-event nethserver-samba-update
[root@neth ~]# echo $?
0
[root@neth ~]# alternatives --list | grep libwbclient
libwbclient.so.0.14-64 manual /usr/lib64/samba/wbclient/libwbclient.so.0.14
The nethserver-samba-update event already ships the fix, but is not automatically triggered by upstream updates. We probably need to cover this scenario with better code.
It is the first time 7.6 receives a samba package update.
The issue could hit only servers updated from 7.5 (or previous) because they have sssd-libwbclient installed. As alternative fix run:
yum remove sssd-libwbclient
systemctl restart winbind
Thanks for helping me find the issue solution!