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File Servers and Domain Controllers
Samba 4.9
Samba suite has been upgraded to 4.9 series. The upgrade brings a number of changes that might affect default configuration or existing deployments.
A detailed set of release notes for Samba 4.9 is available at https://www.samba.org/samba/history/samba-4.9.0.html
Extended attributes support
Since Linux systems have support for extended attributes enabled by default, parameters "map readonly", "store dos attributes" and "ea support" have had their defaults changed to allow better Windows fileserver compatibility in a default install.
smb.conf parameters changes
|Parameter Name|Description|Default

|map readonly
|Default changed

|store dos attributes
|Default changed

|ea support
|Default changed

|Default changed

|Default changed
Identity mapping changes
Over several releases, Samba configuration checks were improved to detect typical identity mapping errors earlier and fail start up before the changes might affect actual operation. With changes in identities causing access control breaches and possibility of a data leakage to unwanted parties, this effort is helping to reduce a number of incorrect but widely deployed cases.
Since Samba 4.6, the 'testparm' tool can be used to validate the ID mapping configuration. After an upgrade please run it and check if it prints any warnings or errors. Please see the 'IDENTITY MAPPING CONSIDERATIONS' section in the smb.conf manpage for suggestions and recommendations. There are some ID mapping backends which are not allowed to be used for the default backend. Winbind daemon will no longer start if an invalid backend is configured as the default backend.
Since Samba 4.8, configurations with "`security = domain`" or "`security = ads`" require a running '`winbindd`' now. The fallback that smbd directly contacts domain controllers is gone.
Finally, Samba 4.9 differentiates between anonymous and guest access via SMB protocol. A side effect of this is that it is now required to have a mapping for `BUILTIN\Guests` group. The mapping can be provided automatically if a default identity backend allows to create entries on demand. Alternatively, `net` utility can be used to provide a group mapping for `BUILTIN\Guests` via
net groupmap add sid=S-1-5-32-546 unixgroup=nobody type=builtin
CTDB configuration changes
Clustered Samba daemon (`CTDB`) configuration has been completely overhauled.
Daemon and tool options are now specified in a new ctdb.conf Samba-style configuration file. See `ctdb.conf(5)` for details.
Event script configuration is no longer specified in the top-level configuration file. It can now be specified per event script. For example, configuration options for the `50.samba` event script can be placed alongside the event script in a file called `50.samba.options`. Script options can also be specified in a new script.options file. See `ctdb-script.options(5)` for details.
Options that affect CTDB startup should be configured in the distribution-specific configuration file. See `ctdb.sysconfig(5)` for details.
Tunable settings are now loaded from `ctdb.tunables`. Using `CTDB_SET_TunableVariable=<value>` in the main configuration file is no longer supported. See `ctdb-tunables(7)` for details.