Question: How can I join Ubuntu 20.04|18.04 to Windows domain?, can I join Debian 10 to Active Directory domain?. This article has been written to show you how to use realmd to join Ubuntu 20.04|18.04 / Debian 10 server or Desktop to an Active Directory domain. Active Directory domain is the central hub for user information in most corporate environments.
For example, in my Company’s infrastructure, it is a key requirement that all users are authenticated to all Linux systems with the Active Directory credentials. This should work for both Debian and Red Hat based Linux distributions. I had earlier written a guide for RHEL / CentOS, check it from the link below.
This guide will illustrate how to configure SSSD to retrieve information from domains within the same Active Directory Resource Forest. if you’re working with more than one AD forest, this guide may not work for you. We’ll also go further and configure sudo rules for the users logging in through AD. Here is a diagram depicted the setup and how the setup works.
So follow below steps to join Ubuntu 20.04|18.04 / Debian 10 To Active Directory (AD) domain.
Step 1: Update your APT index
Start by updating your Ubuntu / Debian Linux system.
sudo apt -y update
This is essential as installations may fail if the server is a freshly installed.
For Ubuntu 20.04|18.04, add the following repositories to your sources.list file.
sudo tee -a /etc/apt/sources.list <<EOF deb http://us.archive.ubuntu.com/ubuntu/ bionic universe deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates universe EOF
Step 2: Set server hostname & DNS
Set a proper hostname for your server with correct domain component.
sudo hostnamectl set-hostname myubuntu.example.com
Confirm your hostname:
$ hostnamectl Static hostname: myubuntu.example.com Icon name: computer-vm Chassis: vm Machine ID: 5beb7ac3260c4f00bcfbe1088f48b8c7 Boot ID: b2a0d9abe43b455fb49484dbaa59dc41 Virtualization: vmware Operating System: Ubuntu 18.04.1 LTS Kernel: Linux 4.15.0-29-generic Architecture: x86-64
Confirm DNS ia configured correctly:
$ cat /etc/resolv.conf
Ubuntu 20.04|18.04 comes with systemd-resolve which you need to disable for the server to access your network DNS directly.
sudo systemctl disable systemd-resolved sudo systemctl stop systemd-resolved
If on DHCP, you can update DNS server manually.
$ sudo unlink /etc/resolv.conf $ sudo vim /etc/resolv.conf
Step 3: Install required packages
A number of packages are required for joining an Ubuntu 20.04|18.04 / Debian 10 system to Active Directory (AD) domain.
sudo apt update sudo apt -y install realmd libnss-sss libpam-sss sssd sssd-tools adcli samba-common-bin oddjob oddjob-mkhomedir packagekit
Only after a successful installation of dependencies can you proceed to discover Active Directory domain on Debian 10 / Ubuntu 20.04/18.04.
Step 4: Discover Active Directory domain on Debian 10 / Ubuntu 20.04|18.04
The realm discover command returns complete domain configuration and a list of packages that must be installed for the system to be enrolled in the domain.
$ sudo realm discover example.com example.com type: kerberos realm-name: EXAMPLE.COM domain-name: example.com configured: no server-software: active-directory client-software: sssd required-package: sssd-tools required-package: sssd required-package: libnss-sss required-package: libpam-sss required-package: adcli required-package: samba-common-bin
Replace example.com with your valid AD domain.
Step 5: Join Ubuntu 20.04|18.04 / Debian 10 To Active Directory (AD) domain
An AD administrative user account is required for integrating your Linux machine with Windows Active Directory domain. Check and confirm AD admin account and the password.
The realm join command will set up the local machine for use with a specified domain by configuring both the local system services and the entries in the identity domain. The command has a number of options which can be checked with:
$ realm join --help
A basic command execution is:
$ sudo realm join -U Administrator example.com Password for Administrator:
- Administrator is the name of admin account used to integrate machine to AD.
- example.com is the name of AD domain
The command first attempts to connect without credentials, but it prompts for a password if required.
View current realmd details.
$ realm list example.com type: kerberos realm-name: EXAMPLE.COM domain-name: example.com configured: kerberos-member server-software: active-directory client-software: sssd required-package: sssd-tools required-package: sssd required-package: libnss-sss required-package: libpam-sss required-package: adcli required-package: samba-common-bin login-formats: %[email protected] login-policy: allow-realm-logins
On RHEL based systems, user’s home directory will be created automatically. On Ubuntu / Debian, you need to enable this feature.
sudo bash -c "cat > /usr/share/pam-configs/mkhomedir" <<EOF Name: activate mkhomedir Default: yes Priority: 900 Session-Type: Additional Session: required pam_mkhomedir.so umask=0022 skel=/etc/skel EOF
Then activate with:
Ensure “activate mkhomedir” is selected, it should have [*]
Then Select <Ok> to save changes.
Your sssd.conf configuration file is located at /etc/sssd/sssd.conf. Whenever there is a change in the file, restart is required.
sudo systemctl restart sssd
Status should be running.
$ systemctl status sssd
If the integration is working, it should be possible to get an AD user info.
$ id jmutai uid=1783929917([email protected]) gid=1784800513(domain [email protected]) groups=1783870513(domain [email protected])
Step 6: Control Access – Limit to user/group
Access to the server enrolled can be limited by allowing only specific users/ and groups.
Limit to users
To permit a user access via SSH and console, use the command:
$ sudo realm permit [email protected] $ sudo realm permit [email protected] [email protected]
Permit access to group – Examples
$ sudo ream permit -g sysadmins $ sudo realm permit -g 'Security Users' $ sudo realm permit 'Domain Users' 'admin users'
This will modify sssd.conf file.
If instead you like to allow all users access, run:
$ sudo realm permit --all
To deny all Domain users access, use:
$ sudo realm deny --all
Step 7: Configure Sudo Access
By default Domain users won’t have permission to escalate privilege to root. Users have to be granted access based on usernames or groups.
Let’s first create sudo permissions grants file.
$ sudo vi /etc/sudoers.d/domain_admins
Add single user:
[email protected] ALL=(ALL) ALL
Add another user:
[email protected] ALL=(ALL) ALL [email protected] ALL=(ALL) ALL
%[email protected] ALL=(ALL) ALL
Add group with two or three names.
%security\ [email protected] ALL=(ALL) ALL %system\ super\ [email protected] ALL=(ALL) ALL
Step 8: Test SSH Access
Access the server remotely as user on AD allowed to login.
$ ssh [email protected] The authenticity of host 'localhost (::1)' can't be established. ECDSA key fingerprint is SHA256:wmWcLi/lijm4zWbQ/Uf6uLMYzM7g1AnBwxzooqpB5CU. ECDSA key fingerprint is MD5:10:0c:cb:22:fd:28:34:c6:3e:d7:68:15:02:f9:b4:e9. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.
- Join Ubuntu 20.04|18.04 to Windows domain
- Join Ubuntu 20.04|18.04 to AD
- Join Ubuntu 20.04|18.04 to Active directory
- Join Ubuntu 20.04|18.04 to Samba domain
- Join Debian 10 to Windows domain
- Join Debian 10 to AD
- Join Debian 10 to Active directory
- Join Debian 10 to Samba domain