RHEL 7/8: Join Active Directory with realm and sssd

Quick one-liner: Join RHEL to Active Directory in four commands — install realmd and sssd, configure auth, join the domain, and set home directory format.

🤔 Why This Matters

When you manage Linux servers in an enterprise, you don't want local accounts on every box. Active Directory gives you centralized authentication — one password, one account, access to everything.

On RHEL 7 and 8, joining AD is straightforward thanks to realmd and sssd. No editing PAM configs by hand, no guessing which packages to install.

🔧 Step 1: Install Required Packages

On a minimal server setup:

sudo yum install realmd sssd samba-common-tools oddjob-mkhomedir

The oddjob-mkhomedir package auto-creates home directories on first login — otherwise AD users can authenticate but get a "no home directory" error.

🔧 Step 2: Enable sssd

sudo authconfig --enablesssd --update

This configures PAM and NSS to use sssd for authentication and user lookups.

🔧 Step 3: Join the Domain

sudo realm join fosstech.biz

You'll be prompted for the AD administrator password. Once authenticated, your system joins the domain.

Verify the join:

realm list

You should see your domain listed with the configured server and client software.

🔧 Step 4: Configure Home Directory Format (Optional)

By default, sssd creates home directories as /home/username. I prefer /home/username@domain so it's clear which domain the user belongs to.

Edit /etc/sssd/sssd.conf:

[domain/fosstech.biz]
fallback_homedir = /home/%u@%d

Where %u is the username and %d is the domain name.

Restart sssd:

sudo systemctl restart sssd

✅ Test the Connection

id [email protected]

You should see the user's UID, GID, and group memberships from Active Directory.

✅ Quick Reference