Trouble Joining an Active Directory Domain

Question

I'm trying to join an Ubuntu 14.04 server to a Windows 2003 R2 domain. My admin says that from the controller side, it is part of the domain. But SSSD can't seem to start and DNS update fails.

I've been following a variety of guides to try and get this working but have been unsuccessful in completing any one of them without errors.

Ubuntu Server Guide
KiloRoot
NetNerds
Fedora SSSD Guide

Discovery seems to be working just fine:

kyle@Server21:~$ realm discover COMPANYNAME.LOCAL
CompanyName.Local
  type: kerberos
  realm-name: COMPANYNAME.LOCAL
  domain-name: companyname.local
  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: %U
  login-policy: allow-realm-logins
companyname.local
  type: kerberos
  realm-name: COMPANYNAME.LOCAL
  domain-name: companyname.local
  configured: no

realmd says that I'm joined to the domain as well:

kyle@Server21:~$ realm join COMPANYNAME.LOCAL
realm: Already joined to this domain

Kerberos took my admin's authentication:

kyle@Server21:~$ kinit -V administrator
Using default cache: /tmp/krb5cc_0
Using principal: administrator@COMPANYNAME.LOCAL
Password for administrator@COMPANYNAME.LOCAL:
Authenticated to Kerberos v5

But when it comes time to join, the DNS Update fails:

kyle@Server21:~$ sudo net ads join -k
Using short domain name -- COMPANYNAME
Joined 'SERVER21' to dns domain 'CompanyName.Local'
No DNS domain configured for server21. Unable to perform DNS Update.
DNS update failed: NT_STATUS_INVALID_PARAMETER

And SSSD is still having an issue starting:

kyle@Server21:~$ systemctl status sssd.service
● sssd.service - System Security Services Daemon
   Loaded: loaded (/lib/systemd/system/sssd.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Wed 2016-06-22 09:57:57 EDT; 37min ago
  Process: 16027 ExecStart=/usr/sbin/sssd -D -f (code=exited, status=1/FAILURE)

Jun 22 09:57:55 Server21 sssd[16038]: Starting up
Jun 22 09:57:55 Server21 sssd[16041]: Starting up
Jun 22 09:57:55 Server21 sssd[16042]: Starting up
Jun 22 09:57:56 Server21 sssd[be[16043]: Starting up
Jun 22 09:57:57 Server21 sssd[be[16043]: Failed to read keytab [default]: No such file or directory
Jun 22 09:57:57 Server21 sssd[16031]: Exiting the SSSD. Could not restart critical service [COMPANYNAME.LOCAL].
Jun 22 09:57:57 Server21 systemd[1]: sssd.service: Control process exited, code=exited status=1
Jun 22 09:57:57 Server21 systemd[1]: Failed to start System Security Services Daemon.
Jun 22 09:57:57 Server21 systemd[1]: sssd.service: Unit entered failed state.
Jun 22 09:57:57 Server21 systemd[1]: sssd.service: Failed with result 'exit-code'.

The only part of krb5.conf that is specific to me is the [libdefaults]:

kyle@Server21:~$ cat /etc/krb5.conf
[libdefaults]
        default_realm = COMAPNYNAME.LOCAL

Though on a previous install I thought there was something else in [realms] but I can't remember what. The Fedora guide talks about adding something there when DNS lookups aren't working but doesn't go into enough detail for me to figure out exactly what is supposed to be there.

My modifications to the smb.conf:

[global]

## Browsing/Identification ###

# Change this to the workgroup/NT-domain name your Samba server will part of
   workgroup = COMPANYNAME
   client signing = yes
   client use spnego = yes
   kerberos method = secrets and keytab
   realm = COMPANYNAME.LOCAL
   security = ads

My sssd.conf

kyle@Server21:~$ sudo cat /etc/sssd/sssd.conf
[sssd]
services = nss, pam
config_file_version = 2
domains = COMPANYNAME.LOCAL

[domain/COMPANYNAME.LOCAL]
id_provider = ad
access_provider = ad
override_homedir = /home/%d/%u

And since the Ubuntu guide says that ownership and permissions are important:

kyle@Server21:~$ sudo ls -la /etc/sssd
total 12
drwx--x--x   2 sssd sssd 4096 Jun 21 14:34 .
drwxr-xr-x 103 root root 4096 Jun 22 10:21 ..
-rw-------   1 root root  172 Jun 21 14:22 sssd.conf

The Ubuntu guide also mentions that the hosts file could cause issues with the DNS updating but I think I've followed their example correctly:

kyle@Server21:~$ cat /etc/hosts
127.0.0.1       localhost
127.0.1.1       Server21
192.168.XXX.XXX Server21 Server21.COMPANYNAME.LOCAL

# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

So where am I going wrong here? The domain controller says it is part of the domain. I have Apache and OpenSSH both up and accessible. But there is a lot more this server is going to do and so I want to make sure everything is configured properly before moving forward.

---

Edit:

I changed my hosts file based on advice from this page so that it looks like this now:

kyle@Server21:~$ cat /etc/hosts
127.0.0.1       localhost
127.0.1.1       Server21.COMPANYNAME.LOCAL Server21
192.168.11.11   Server21.COMPANYNAME.LOCAL Server21

# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Now getent returns:

kyle@Server21:~$ sudo getent hosts Server21
127.0.1.1       Server21.COMPANYNAME.LOCAL Server21 Server21
192.168.11.11   Server21.COMPANYNAME.LOCAL Server21 Server21

And net ads join now has a different error message:

kyle@Server21:~$ sudo net ads join -k
Failed to join domain: failed to lookup DC info for domain 'COMPANYNAME.LOCAL' over rpc: An internal error occurred.

So far the only advice I've found on this error says to make sure that the AD server is in resolv.conf and it's IP is the only entry.

kyle@Server21:~$ cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 192.168.XXX.XXX

To answer a comment:

kyle@Server21:~$ nslookup -type=SRV _ldap._tcp.companyname.local
Server:         192.168.XXX.XXX
Address:        192.168.XXX.XXX#53

_ldap._tcp.companyname.local      service = 0 100 389 companynamedc.companyname.local.

Somewhere along the way SSSD was able to start and is now active. Though I'm unsure of what I've done that fixed it.

Answer 1

The problem seems to have been that my admin had created an entry on the Domain Controller for this server. This apparently caused a conflict that caused Kerberos to encounter the following error when trying to join:

kyle@Server21:~$ sudo net ads join -k
Failed to join domain: failed to lookup DC info for domain 'COMPANYNAME.LOCAL' over rpc: An internal error occurred.

I'm not sure that this error was entirely accurate since my admin said the server was joined to the domain on his end and realmd indicated that I was joined as well:

kyle@Server21:~$ realm join COMPANYNAME.LOCAL
realm: Already joined to this domain

The steps I followed to get a successful Kerberos join were as follows:

1. Admin removed the entry in the Domain Controller
2. Reran Kerberos configuration using: sudo dpkg-reconfigure krb5-config
3. Chose the options in the configuration to add the Domain Controller explicitly to the [realms] section of krb5.conf
4. Changed the hostname to ensure a new record was created
5. Pulled a new ticket using kinit
6. Joined the domain using sudo net ads join -k

Final result:

kyle@SERV21:~$ sudo net ads join -k  
Using short domain name -- COMPANYNAME  
Joined 'SERV21' to dns domain 'CompanyName.Local'