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Fedora 28 https://fedoraproject.org/wiki/Changes/Deprecate_TCP_wrappers[removes support] for `tcp_wrappers` (aka `/etc/hosts.deny` access files) by default from all the network daemons and tools. The preferred replacements are software firewalld, nftables rules or software specific access rules for more complex filtering. If your system security depends on `tcp_wrappers` rules, convert them to firewall rules, or set up `tcpd` to do the same job for you.
Fedora 28 replaces authconfig with authselect as the default tool for generating PAM configuration files and nsswitch.conf. On new installations, authselect, together with an authconfig compatibility tool, will be installed by default instead of authconfig. On upgraded installations, authconfig will be replaced with authselect and the compatibility tool but the configuration generated by authconfig will be left intact. The authconfig compatibility tool will be removed from Fedora in a future release. The https://github.com/pbrezina/authselect/tree/master/src/man/authselect-migration.7.txt.in.in[authselect-migration(7)] man page explains how to migrate from authconfig to authselect.
Fedora has https://fedoraproject.org/wiki/Changes/Deprecate_TCP_wrappers[deprecated the use of TCP wrappers]. The OpenLDAP project also https://www.openldap.org/doc/admin24/security.html#TCP%20Wrappers[discourages their use] and recommends that an IP firewall is used instead. With this update, OpenLDAP will not be configured with `--enable-wrappers` and so any TCP wrappers configuration will have no effect on OpenLDAP. Other means should be used to protect the OpenLDAP server.
Unless an application explicitly requests either the DBM or SQL format, the NSS library will automatically migrate the application's NSS database from the old to the new format. The old database files will not be updated further. Most users should not experience differences in operation. Applications that perform many NSS read/write operations may experience a minor performance decrease. Use the following command to trigger an explicit migration:
Users who store their system home or application data directory on a network filesystem are advised to set the `NSS_SDB_USE_CACHE=yes` environment variable prior to starting applications that use NSS. Without setting this environment variable, users of network filesystems may experience a major slowdown with some applications, such as Firefox. The environment variable enables the use of a caching strategy in NSS that works around the slowness of network filesystems. Because this caching strategy causes a performance decrease on fast filesystems.
With this update, the OpenLDAP distribution in Fedora changed from using the *NSS* (or *MozNSS*) library to the *OpenSSL* library for providing cryptographic functions. The switch promises better support from OpenLDAP upstream, which had ceased maintaining the NSS support layer.