[Samba] I can't join the Windows client to my Samba DC.

[Jason Long]

Hello,
I installed and configured my Samba DC and after it, I configured a DHCP server with below configuration:

# cat /etc/dhcp/dhcpd.conf 

default-lease-time 600;
max-lease-time 7200;
ddns-update-style none;
authoritative;
subnet 192.168.56.0 netmask 255.255.255.0 {
range 192.168.56.8 192.168.56.254;
option routers 192.168.56.7;
option subnet-mask 255.255.255.0;
option domain-name-servers 192.168.56.7, 8.8.8.8;
}

Some information about my server are as below:

# cat /etc/resolv.conf 
search mydomain.z
nameserver 192.168.56.7

# cat /etc/hosts 
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.56.7 mydc.mydomain.z mydc

# ifconfig
enp0s8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.3.15  netmask 255.255.255.0  broadcast 10.0.3.255
        inet6 fe80::a00:27ff:fedb:4c29  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:db:4c:29  txqueuelen 1000  (Ethernet)
        RX packets 2767  bytes 1571542 (1.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2225  bytes 248647 (242.8 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0


enp0s17: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.56.7  netmask 255.255.255.0  broadcast 192.168.56.255
        inet6 fe80::4d0f:9f8b:8077:22cd  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:76:82:f7  txqueuelen 1000  (Ethernet)
        RX packets 743  bytes 71185 (69.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 274  bytes 28911 (28.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0


lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 4967  bytes 559670 (546.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 4967  bytes 559670 (546.5 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0


Windows client gave an IP address from the DHCP server. When I want to join Windows client to my Linux domain, then I got below error:
https://i.postimg.cc/WbxnNTmt/Server-2.png

Why? Which log must be examined?

Thank you.