Installing and configuring NTP Chrony for Samba-AD on Redhat and derivatives

Hint

Active Directory is based on the Kerberos protocol which requires near perfect clock synchronization between the domain member workstations and the Samba-AD domain controller. NTP is used to ensure synchronization between the clocks of the different devices on the network.

Install the Chrony NTP packages and choose a time server on the Internet (on a standard Redhat installation, Chrony is already installed, it replaces the historical ntpd daemon):
```
yum install ntpdate chrony
ntpdate -bu pool.ntp.org
```
Add the following lines to /etc/chrony.conf to manage the signed NTP used by Windows workstations to automatically synchronize their clocks with the AD server:
```
ntpsigndsocket  /var/lib/samba/ntp_signd
```
Change the owner of the directory containing the samba socket used to authenticate the NTP service:
```
chown root:chrony /var/lib/samba/ntp_signd/
chmod 750 /var/lib/samba/ntp_signd/
```
Restart Chrony:
```
systemctl restart chronyd
```

Forcing a resynchronization on a windows workstation

Run the following command in a shell with admins rights which asks the local windows ntp client server to sync. If all goes well, the command returns The command ended correctly). Note: it is necessary to give an NTP server some time before asking it for its time, otherwise it declares itself as not being a reliable source.

w32tm /resync /nowait

In the event of a problem

The service is called w32time while the management tool is called w32tm. You may also need the net time command.

Reconfigure windows workstations to use AD for NTP.

On the Windows workstation, launch the following instructions:

w32tm /config /syncfromflags:domhier
w32tm /config /update
w32tm /resync /nowait

Debugging the NTP client on windows

To debug the client, the following registry keys can be defined (http://support.microsoft.com/kb/816043/en-us):

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Config]
"FileLogSize"=dword:01000000
"FileLogName"="c:\\w32time_debug.txt"
"FileLogEntries"="0-300"

The two modes of operation of the windows NTP client

Operation in ADS client mode, Nt5DS mode. It is in this mode that one must be with a Samba-AD domain:
```
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters]
...
"Type"="Nt5DS"
```

Operation in named NTP mode. To switch to this mode, type net time /setsntp:srvads.mydomain.lan:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W32Time\Parameters]
...
"Type"="NTP"
"ntpserver"="srvads.tranquilit.lan"

Check that the NTP client is pointing to the correct server. In case the dhcp gives an ntp that is not the domain controller, this can also be a problem. To check this, you can use the following command:
```
w32tm /monitor
```

The NTP service does not seem to take into account your ntp.conf configuration

Check that there is not a /var/lib/ntp/ntp.conf.dhcp file, and delete it if so. This file was created by dhclient before the server was switched to a fixed IP.
```
rm -f /var/lib/ntp/ntp.conf.dhcp
```

Now we can install Samba in Active Directory mode. We’re progressing, that’s good!