AD authentication is a popular mechanism for login and user authentication. It works very well in many scenarios, especially for enterprise applications. AD authentication is a supported scenario on SQL Server on Linux. Configuring the Linux VM to join with Active Directory (AD) can be a little tricky at sometimes though, especially in a complex enterprise environment.
- One error message you may see from “realm join” is “realm: Couldn’t join realm: This computer’s host name is not set correctly.” This is due to a generic hostname (e.g. “localhost”), an incorrect domain in your hostname (e.g. “host1.abcd.com” instead of “host1.contoso.com”), or a duplicate hostname on the domain. To fix this, edit /etc/hostname to have a unique hostname and reboot the machine. On Ubuntu, it can also be helpful to put the fully qualified domain name in /etc/hostname (e.g. “host1.contoso.com” instead of “host1”).
Another possibility is that if the DNS is configured incorrectly, the host may be unable to resolve the domain. This will result in the message “realm: No such realm found” being returned from “realm join” command. To fix this, you need to use a DNS server on the realm you wish to join (can be on the same machine as the domain controller). The steps to fix this are described here: https://docs.microsoft.com/en-us/sql/linux/sql-server-linux-active-directory-authentication?view=sql-server-2017#join
They provide in this post some of the low-hanging fruit answers, where the problem is in basic server configuration.