Ubuntu 18.04 Join Active Directory Domain

Install required tools:

sudo apt install krb5-user samba sssd chrony

Kerberos

Modify the Kerberos config:

sudo nano /etc/krb5.conf

[libdefaults]
default_realm = DOMAIN.COM
ticket_lifetime = 24h
renew_lifetime = 7d

Time Sync

Modify the Chrony config:

sudo nano /etc/chrony/chrony.conf

Comment out existing servers and add domain controller (or other time servers):

server dc.domain.com iburst

Samba

Modify the samba config:

sudo nano /etc/samba/smb.conf

[global]
workgroup = DOMAIN
client signing = yes
client use spnego = yes
kerberos method = secrets and keytab
realm = DOMAIN.COM
security = ads

SSSD

No default SSSD config exists, create it:

sudo nano /etc/sssd/sssd.conf

[sssd]
services = nss, pam
config_file_version = 2
domains = DOMAIN.COM

[domain/DOMAIN.COM]
id_provider = ad
access_provider = ad

# Use this if users are being logged in at /.
# This example specifies /home/DOMAIN-FQDN/user as $HOME. Use with pam_mkhomedir.so
override_homedir = /home/%d/%u
override_shell = /bin/bash

Set permissions to config file:

sudo chown root:root /etc/sssd/sssd.conf
sudo chmod 600 /etc/sssd/sssd.conf

Join Domain

Restart services to apply configuration changes:

sudo systemctl restart chrony.service
sudo systemctl restart smbd.service nmbd.service
sudo systemctl start sssd.service

Test the configuration by obtaining a Kerberos ticket:

sudo kinit Administrator

Verify the ticket with:

sudo klist

If there is a ticket with an expiration date listed, then it is time to join the domain:

sudo net ads join -k

Autocreate Home Directory

Since no home directory exists for domain users, create on login:

sudo nano /etc/pam.d/common-session

Directly after session required pam_unix.so:

session required pam_mkhomedir.so skel=/etc/skel/ umask=0022

You should be able to login as a domain user now and have a home directory.
If login isn’t working, try rebooting the server first to refresh all services and try logging in again.