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Fixing Ubuntu 20.04 AD Join Failure

Ubuntu 14

In this article, we will delve into a common issue encountered by system administrators while attempting to join a Ubuntu 20.04 machine to a Windows Active Directory (AD) domain. The error message “Couldn’t get kerberos ticket for: Administrator@EXAMPLE.ORG: New password cannot be zero length” often indicates that the domain user’s password is set to be changed on the next login. We will guide you through the steps to resolve this issue.

Quick Answer

To fix the Ubuntu 20.04 AD join failure issue, you need to change the domain user’s password using the kinit command and then join the Ubuntu machine to the Windows AD domain using the realm join command.

Understanding the Problem

When you try to join a Ubuntu 20.04 machine to a Windows AD domain using the realm join command, you might encounter an error. This error typically suggests that the domain user’s password needs to be changed before joining the domain. This can be confirmed by checking if the “Must change password on the next login” option is enabled for the domain user.

Solution Steps

To resolve this issue, you need to follow two main steps:

1. Change the Domain User’s Password

The first step is to change the domain user’s password. You can do this by using the kinit command. This command is used to obtain and cache Kerberos ticket-granting tickets.

In a terminal, run the following command:

kinit Administrator@EXAMPLE.ORG

Replace EXAMPLE.ORG with your actual domain name. After running this command, you will be prompted to enter the current password for the domain user. Enter the password and press Enter.

If the password is successfully authenticated, you will be able to proceed to the next step. Otherwise, double-check the password and try again.

2. Join the Ubuntu Machine to the Windows AD Domain

After changing the domain user’s password, the next step is to join the Ubuntu machine to the Windows AD domain. You can do this by using the realm join command.

In the terminal, run the realm join command with the -v option for verbose output:

sudo realm join -v example.org

Replace example.org with your actual domain name. After running this command, you will be prompted to enter the password for the domain user. Enter the new password that you set in the previous step and press Enter.

The realm join command will attempt to join the Ubuntu machine to the Windows AD domain. If successful, you will see a confirmation message. Otherwise, check the error message for any specific issues and troubleshoot accordingly.

Conclusion

By following these steps, you should be able to join the Ubuntu 20.04 machine to the Windows AD domain successfully. Remember, the key is to ensure that the domain user’s password is changed before attempting to join the domain.

For more information on the realm command and its various options, you can check the official documentation. If you encounter any other issues, feel free to consult the Ubuntu community for further assistance.

What is the purpose of joining a Ubuntu machine to a Windows Active Directory domain?

Joining a Ubuntu machine to a Windows Active Directory domain allows for centralized user authentication and access control. It enables users to log in to the Ubuntu machine using their domain credentials and provides seamless integration with other domain resources such as file shares and printers.

How do I check if the “Must change password on the next login” option is enabled for a domain user?

To check if the "Must change password on the next login" option is enabled for a domain user, you can use the adtool command. Run the following command in a terminal:

adtool user-info username

Replace username with the actual username of the domain user. Look for the "Password must change" field in the output. If it is set to "Yes," the option is enabled for the user.

Can I change the password for a domain user without using the `kinit` command?

Yes, you can change the password for a domain user using other methods such as the passwd command or through the Windows Active Directory administration tools. However, in the context of resolving the "Couldn’t get kerberos ticket" error, using the kinit command is recommended to ensure proper authentication and ticket-granting.

What should I do if I encounter an error while running the `realm join` command?

If you encounter an error while running the realm join command, carefully review the error message for any specific information about the issue. Common issues include incorrect domain name, network connectivity problems, or conflicting configurations. Troubleshoot accordingly by verifying the domain name, checking network connectivity, and ensuring the correct configuration settings.

Are there any additional configuration steps required after joining the Ubuntu machine to the Windows AD domain?

After successfully joining the Ubuntu machine to the Windows AD domain, you may need to configure additional settings depending on your requirements. This may include configuring SSSD for user and group resolution, configuring access control through group policies, or configuring domain-based file shares. Refer to the official documentation or consult with your system administrator for further guidance.

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