Ubuntu 14.04 Ultimate Server Guide

Part 10: Secondary Server – DHCP & DNS

It’s now time to consider adding a secondary server into the mix to provide DHCP, DNS, LDAP and Kerberos services in the event of failure/maintenance of the primary server. In this case a stock install of 12.04 server is being used with the hostname morpehus.danbishop.org

First ensure that you have set a static IP address for the secondary server. This is done by editing /etc/network/interfaces like so:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
        address 192.168.0.3
        netmask 255.255.255.0
        network 192.168.0.0
        broadcast 192.168.0.255
        gateway 192.168.0.1

Now would be a good time to tell the primary server (neo) about the secondary server (morpehus). As morpheus won’t be requesting its IP address using DHCP, it won’t automatically be mapped to DNS. We can change this by adding the following line to the bottom of /etc/dnsmasq.conf on neo.

# DNS for secondary server           
ptr-record=3.0.168.192.in-addr.arpa.,"morpheus.danbishop.org"
address=/morpheus.danbishop.org/192.168.0.3

We should also add morpheus as a secondary DNS server by modifying the DNS section of that file like so:

#DNS Settings
server=/#/192.168.0.2
server=/#/192.168.0.3
server=/#/8.8.8.8
server=/#/8.8.4.4

Notice that we’ve changed from server=/localnet/ to server=/#/ for our two local DNS servers. Using the localnet parameter meant that dnsmasq would only check /etc/hosts and DHCP clients, now however, some DHCP clients are being handled by one server and some by the other, therefore, it’s essential that both servers check each other for local clients.

By default, dnsmasq only provides one DNS server to DHCP clients, that being itself. We want it to provide both itself and the new secondary server so we’ll also add the line:

#provide dhcp clients with both primary and secondary dns 
dhcp-option=6,0.0.0.0,192.168.0.3

This means that neo’s /etc/dnsmasq.conf file now looks like this:

#Use dnsmasq specific hosts file
no-hosts
addn-hosts=/etc/hosts.dnsmasq
#DNS Settings
server=/#/192.168.0.2
server=/#/192.168.0.3
server=/#/8.8.8.8
server=/#/8.8.4.4
#provide dhcp clients with both primary and secondary dns 
dhcp-option=6,0.0.0.0,192.168.0.3
#
# adapted for a typical dnsmasq installation where the host running
# dnsmasq is also the host running samba.
# you may want to uncomment some or all of them if you use
# Windows clients and Samba.
dhcp-option=19,0           # option ip-forwarding off
dhcp-option=44,0.0.0.0     # set netbios-over-TCP/IP nameserver(s) aka WINS ser$
dhcp-option=45,0.0.0.0     # netbios datagram distribution server
dhcp-option=46,8           # netbios node type
#
domain=danbishop.org                            #sets the domain name you're going to use
dhcp-range=192.168.0.50,192.168.0.150,12h       #sets the range from which to allocate IP addresses to clients and the lease time
dhcp-option=option:router,192.168.0.1           #sets the IP address of the router (gateway address) to be given to clients
dhcp-option=option:ntp-server,192.168.0.2 #sets the NTP server to 192.168.0.2
dhcp-authoritative                              #makes this the authoritative (in this case ONLY) DHCP server on the network
#
# Server DNS settings... this is required as the server itself will
# not be obtaining it's IP address via DHCP and therefore would
# not be automatically added to the DNS records for forward/reverse
# DNS queries as required by Kerberos
ptr-record=2.0.168.192.in-addr.arpa.,"neo.danbishop.org"
address=/neo.danbishop.org/192.168.0.2
#
# Kerberos and LDAP automatic stuff...
# This maps kerberos.danbishop.org and
# ldap.danbishop.org to the server and also makes all
# dhcp clients aware of the kerberos realm... magic 😀
address=/kerberos.danbishop.org/192.168.0.2
address=/ldap.danbishop.org/192.168.0.2
#
txt-record=_kerberos.danbishop.org,"DANBISHOP.ORG"
srv-host=_kerberos._udp.danbishop.org,"kerberos.danbishop.org",88
srv-host=_kerberos._tcp.danbishop.org,"kerberos.danbishop.org",88
srv-host=_kerberos-master._udp.danbishop.org,"kerberos.danbishop.org",88
srv-host=_kerberos-adm._tcp.danbishop.org,"kerberos.danbishop.org",749
srv-host=_kpasswd._udp.danbishop.org,"kerberos.danbishop.org",464
#
srv-host=_ldap._tcp.danbishop.org,ldap.danbishop.org,389
#
# DNS for secondary server
ptr-record=3.0.168.192.in-addr.arpa.,"morpheus.danbishop.org"
address=/morpheus.danbishop.org/192.168.0.3

Secondary DHCP

There are several possible approaches to this, the enterprise-style approach would involve ditching dnsmasq and setting up ISC BIND and DHCP… however, this is very complicated and total overkill for a home/small business setup. Instead, we’re going for the simple approach. Two, equally authoritative DHCP servers serving different IP ranges. If you’ve been following this guide from the beginning, your primary server (neo) will be serving up IPs in the range 192.168.0.50-192.168.0.150, therefore we’ll set the secondary server (morpheus) to serve from 192.168.0.151-192.168.0.250

When both servers are up, it doesn’t matter which provides a new machine with its IP address first. If only one server is running, all new machines will be served IPs from only that server’s range.

sudo apt-get install dnsmasq

Now we’ll configure dnsmasq in the exact same way as neo, with the ip range changed as discussed and also dhcp option 6 set to provide neo as the primary dns server and morpheus as a backup.

sudo nano /etc/dnsmasq.conf
#Use dnsmasq specific hosts file
no-hosts
addn-hosts=/etc/hosts.dnsmasq
#DNS Settings
server=/#/192.168.0.2
server=/#/192.168.0.3
server=/#/8.8.8.8
server=/#/8.8.4.4
#provide dhcp clients with both primary and secondary dns 
dhcp-option=6,192.168.0.2,0.0.0.0
#
# adapted for a typical dnsmasq installation where the host running
# dnsmasq is also the host running samba.
# you may want to uncomment some or all of them if you use
# Windows clients and Samba.
dhcp-option=19,0           # option ip-forwarding off
dhcp-option=44,0.0.0.0     # set netbios-over-TCP/IP nameserver(s) aka WINS ser$
dhcp-option=45,0.0.0.0     # netbios datagram distribution server
dhcp-option=46,8           # netbios node type
#
domain=danbishop.org                            #sets the domain name you're going to use
dhcp-range=192.168.0.151,192.168.0.250,12h       #sets the range from which to allocate IP addresses to clients and the lease time
dhcp-option=option:router,192.168.0.1           #sets the IP address of the router (gateway address) to be given to clients
dhcp-option=option:ntp-server,192.168.0.2 #sets the NTP server to 192.168.0.2
dhcp-authoritative                              #makes this the authoritative (in this case ONLY) DHCP server on the network
#
# Server DNS settings... this is required as the server itself will
# not be obtaining it's IP address via DHCP and therefore would
# not be automatically added to the DNS records for forward/reverse
# DNS queries as required by Kerberos
ptr-record=2.0.168.192.in-addr.arpa.,"neo.danbishop.org"
address=/neo.danbishop.org/192.168.0.2
#
# Kerberos and LDAP automatic stuff...
# This maps kerberos.danbishop.org and
# ldap.danbishop.org to the server and also makes all
# dhcp clients aware of the kerberos realm... magic 😀
address=/kerberos.danbishop.org/192.168.0.2
address=/ldap.danbishop.org/192.168.0.2
#
txt-record=_kerberos.danbishop.org,"DANBISHOP.ORG"
srv-host=_kerberos._udp.danbishop.org,"kerberos.danbishop.org",88
srv-host=_kerberos._tcp.danbishop.org,"kerberos.danbishop.org",88
srv-host=_kerberos-master._udp.danbishop.org,"kerberos.danbishop.org",88
srv-host=_kerberos-adm._tcp.danbishop.org,"kerberos.danbishop.org",749
srv-host=_kpasswd._udp.danbishop.org,"kerberos.danbishop.org",464
#
srv-host=_ldap._tcp.danbishop.org,ldap.danbishop.org,389
#
# DNS for secondary server
ptr-record=3.0.168.192.in-addr.arpa.,"morpheus.danbishop.org"
address=/morpheus.danbishop.org/192.168.0.3

Don’t forget to create /etc/dnsmasq.hosts on the secondary server to stop /etc/hosts interfering with DNS:

sudo touch /etc/hosts.dnsmasq
  • Florent

    Hi Dan !
    Thank you for your great work, as usual 🙂

    I have an error on part 7, like another follower of your 12.04 guide (http://www.danbishop.org/2012/06/02/ubuntu-12-04-ultimate-server-guide/#comment-1552860993).
    Command kadmin -p dan/admin -q “addprinc -randkey nfs/$(hostname -f)” failed with :
    Authenticating as principal dan/admin with password.
    kadmin: Cannot resolve network address for admin server in requested realm while initializing kadmin interface

    Moreover, after restart sssd, it is impossible to connect to LDAP user with su, and getent passwd only shows local user.
    I think there is a problem between client and server. Evertyhing works fine on server side, and client can ping server through kerberos.domain.local and ldap.domain.local.

    Thank you for your help

    • danbishop88

      Hi Florent,

      Try appending -s kerberos.domain.local to that command and see what happens. It looks like you’re customising some parts of the guide for your own environment, but not others… it’s possible that your /etc/krb5.conf file on the client is wrong.

      I’m hoping to have a way of doing all of this using puppet going very soon. I’m almost there and will hopefully publish in the next couple of weeks. That should eliminate all the problems people are having by varying parts of the guide for their environment, but not others.

      Dan

      • Florent

        Thank you very much for your answer.
        I reinstall server & client. No customising except domain (domain.local) and kerberos username as florent/admin. On the client side, sudo dpkg-reconfigure krb5-config only ask realm but server and admin server where difined during installation. My /etc/krb5.conf file seems to be good. My domain isn’t defined in [domain_realm] but it is in [libdefaults]. Servers name are in top of [realms] (kdc and admin_server).
        Is there au place where krb logs ?

        Thanks again.
        Florent

    • Hi Florent,

      i run accoss the same problem as you have, after several tryout found out that you need to point you DNS Client into IP of Server.

      ie. DNS Client is : 8.8.8.8 from Network Manager, then you change to 192.168.1.100 (IP of Ubuntu Server)

      and voila :)… Hope this helps !

    • aqw

      I also got this error and solved it by adding 192.168.0.2 kerberos.danbishop.org to /etc/hosts of the client machine

    • OleHoppe

      Solved this issue by editing /etc/nsswitch.conf on the client (kubuntu 16.04.2). Modify “hosts” line to read:
      hosts: files dns
      HTH

  • Marco

    Hi Dan, thanks for this beatifoul guide

    i try many times your guide but have some problem

    server configure as your guide
    when try login from a configured client (using server username) it log succesfull but unable to mount home directory

    “Could not chdir to home directory /home/fabio: No such file or directory”

    check and check again but still this problem….

    can you help me?

    • Marco

      I have only linux (debian) pc, i’m interested central accounting and share users home directory… samba in future (now not important)

      ubuntu 14 server configure as your VERY clear guide (and thanks!!)
      i’m able lo ssh login on server using LDAP user accounts and is fantastic

      then want allow login from clients, pc… configure as guide… login is accepted but NO home directory mounted

      how i can debug where problem is?

      Sorry for my english

      • GuiSenges

        Hello Marco,

        I got the same problem. Any news? I’ve double checked this tutorial multiple times and everthing seems ok…

        • GuiSenges

          Small Update: When running automount in verbose mode I get “mount(nfs): no hosts available”. NFS server is up and running…Very strange…

        • GuiSenges

          Ok, I figured it out: Ports 111 and 2049 both TCP and UDP needs to be openned….Thanks for the excelent tutorial Dan!

        • Marco

          In my case there was no firewall…

        • Marco

          Problem solved, was a problem with reverse resolution… because i have an existing bind dns server and need use it, can’t use dnsmasq. Now NFS/kerberos works perfect!!
          Tanks for this perfect, clean guide DAN!!

          Now going on to configure samba, but i have a problem again (sorry!!): windows PC can see samba share but can join to samba domain. When try to join samba domain from a windows pc, it ask user name and password (i use my user (domainuser) with net rpc rights grant) but give me an error… each username and password i try to use same error…

    • Hi Marco,

      i have the same situation as you are, can you help me out the solutions here ?

  • Marco

    Hi again,
    i have this strange problem:

    if i reinstal ubuntu on server, add again ldap users, kerberos etc etc (as in this guide)

    clients can’t mount their home using nfs

    try to login one from client, perform again:
    kadmin -p dan/admin -q “addprinc -randkey nfs/$(hostname -f)”
    sudo kadmin -p dan/admin -q “ktadd nfs/$(hostname -f)”
    but nothink happens

    if i reinstall ubuntu on client pc, follow client configuration (of this guide) all return perfect working

    I think problem is Kerberos, but how to solve this problmem when i reinstall OS on server?
    try to remove nfs princ from server but not solution

    any advices?
    thanks

    • Hi Marco,

      happens to be the same issue with me as well,
      but instead of reformatting ubuntu client, here are what i did :

      apt-get purge –remove krb5-user -y
      REBOOT NOW !

      apt-get install krb5-user -y
      dpkg-reconfigure krb5-config

      sudo kadmin -p dan/admin -q “addprinc -randkey nfs/$(hostname -f)”
      sudo kadmin -p dan/admin -q “ktadd nfs/$(hostname -f)”

      REBOOT NOW !

      and you can easily login with your domain users credentials 🙂

      (PS : your guess is right it is somehow connected to Kerberos, but no need to remove nfs princ 🙂

      • Marco

        Hi,
        thanks for this solution!

  • Steve Thompson

    Hi,
    Thanks for the great guide. I have a question about this setup – I also had this problem with the 12.04 guide. In both, you set neo to have a static IP and then you configure dnsmasq to use Google’s public servers. At no point, as far as I can see, do you tell neo which DNS servers to use which means it has no DNS. I’ve added dns-nameservers 127.0.0.1 to the static config to get round this but I can’t figure out if I’m missing something in the instructions that would make this unnecessary?

    Thanks

  • Hi Dan, just a quick correction,

    on Page 6
    there is something like

    #BINDPWDFILE=”/etc/ldapscripts/ldapscripts.passwd”

    it should be not comment (remove the hashtag)

    otherwise it will come out results

    “Unable to read password file , exiting…”

    But overall this is Awesome tutorials :))

    • Thanks Adhi… I had the same issue. Great guide by the way, Dan 😀

  • Marco

    Hi, i have new problem

    new workstation wit Windows 10 need to be joined to Samba

    not no succes 🙁

    no problem when add windows7 macchines

  • Ian Carey

    The package ldapscripts didn’t work for me. I used ldap-account-manager instead.

    For Samba, by default you get Samba 4. Your command “adminlocal@neo:$ net rpc rights grant -U dan “danbishop.orgDomain Admins” SeMachineAccountPrivilege SePrintOperatorPrivilege SeAddUsersPrivilege SeDiskOperatorPrivilege SeRemoteShutdownPrivilege” is depreciated and will not work with Samba 4.

    Fix is a new syntax below.

    net sam rights grant “danbishop.orgDomain Admins” SeMachineAccountPrivilege SePrintOperatorPrivilege SeAddUsersPrivilege SeDiskOperatorPrivilege SeRemoteShutdownPrivilege -Udan

    Other than those two things I have it all up and running perfectly. Thank you Dan!

  • Jheguy2

    I’ve been getting the error:
    Error adding group domainadmins to LDAP
    every time I try and create a new group. I’ve checked the logs and they are returning:
    ldap_add: No such object (32)
    If anyone could help me I would be more than grateful. Thank you.

    • Pekka R.

      Had similar problem. Did not check the logs, so not completely sure if same problem.
      I commented line BINDDN=”cn=Manager,dc=example,dc=com” from

      /etc/ldapscripts/ldapscripts.conf
      since similar line was already added for actual DN by Dan’s instructions.

    • Dheeraj Bharat Sethi

      Hi there, In just faced the same issue, can you please let me know the solution for the same?
      Thanku

      • Dheeraj Bharat Sethi

        Got it resolved, adding password by vi was causing the issue.

  • Olivier Dir

    hi all after client install (ubuntu 14.04) without error
    i don’t found domainadmins with command getent group
    how do to debug this point ?

    where is the log file for see if there are a problem ?

    thank for your help

  • Marco

    All works fantastic (10months perfect working)
    but now i have new workstation with windows10 preinstalled, want join them tho ubuntu domain
    follow same guide than win7 but win10 give me an error, not join into domain giving an error (unable to contact domain)

    any help?

  • Kleder Osodarck

    Hello Dan!

    First thanks for the great tutorial!

    I’m using your guide to build an GNS3 network for a college project, the problem is I have to join Windows XP and 2000 machines in the domain, any information or direction on how to do so will be really appreciated! below is the error I’m receiving in a Windows XP machine:

    error 0x000005B4 ERROR_TIMEOUT

  • John Christensen

    I am not having luck getting Windows 7 to connect to the Samba DC. The error I am getting says that windows was trying to contact the SRV record for _ldap._tcp.dc._msdcs.. I added a SVR record to dnsmasq.conf and pointed the requests to ldap. on port 398. Now I am getting an error from Windows that the domain controller at ldap. could not be reached. Any thoughts on why this is not working for me?

  • TC

    On Ubuntu 15.10, I failed at Step 6, “sudo ldapaddgroup domainadmins”. In /var/log/ldapscripts.log, the error message is ldapadd: invalid format (line 1) entry “”. It turns out it is a bug in ldapscripts—it fails in some locales. For more information, read this:

    https://github.com/martymac/ldapscripts/issues/3

    You can fix this bugs by these commands:

    sudo su
    LC_ALL=C ldapaddgroup domainadmins
    LC_ALL=C ldapaddgroup domainusers
    LC_ALL=C ldapadduser csatc2002 domainadmins
    LC_ALL=C ldapaddusertogroup csatc2002 domainusers

    Just my two cents, and hope it helps.

  • Thanks a lot, Dan.
    I migrated the authentication of a cluster of machines with Ubuntu 14.04 from NIS to LDAP+Kerberos and it worked great. I tried to follow the instructions for SingleSignOn from the Ubuntu Help but it was very complicated, didn’t explain some concepts and contained some “magical” instructions. This guide help me figure out what I needed to do.

  • Srinath Bk

    Hi Dan,

    thanks for the excellent tutorial.

    I cannot use DHCP server for my setup since, there is already another DHCP server in the LAN. I would like to use static IP for both server and clients. Can you please suggest what needs to be changed?

    regards,
    Srinath

  • Dheeraj Bharat Sethi

    Hi dan,
    Thanku so much for the guide.
    been stuck on last step. when trying to login via the new ldap user.
    “No passwd entry for user”
    When trying to add passwd, “user does not exist”
    What is going wrong here?
    Thanku

  • Dheeraj Bharat Sethi

    Getting Permission Denied via SSH for the Ldap user added , and Incorrect Login via server login

  • Hello Dan,

    Are there any GUI based apps for managing Sudoer Rules in LDAP? Using a
    LDAP Browser is not a very user-friendly way for managing a large number
    of Sudo Rules. FreeIPA has a UI for managing Sudoer Rules, but it
    requires 389 Directory Server, and we don’t use that in our environment
    (for good reasons)

  • Bineural juls

    Hi, i think all its working ok, but as sson as i login by ssh with user i have this error.. Could not chdir to home directory /home/robert: No such file or directory
    And localy on the machine this one:
    No directory, logging in with HOME=/
    I can see the problem is that my home is not working.. but i dunno how to solve this.
    Any idea please?
    Thanks a lot

  • Pekka R.

    Salut!
    This is still the most clear and complete guide to set up a small company network environment with servers. I can not find better. And I have looked around. Just bloody exellent. “Ultimate” describes this well.
    Did finally have time to look at chapter 10. Just wondering what does mean “In this case a stock install of 12.04 server is being used” in this context.

    Dan? Does it mean a copy of the primary server installation that I could make with dd command and then twist around the dnsmasq configuration file?

    Maybe safest option is to start installing server from the start and follow up the master server setup instructions untill this point. I expect that the /etc/dnsmasq.conf file will be mirror of the master dnsmasq server regarding to ip-adresses and host names. Will start playing with image copied with dd first.

    Many thanks to Dan for giving this to public domain. To boil up this kind of instruction set so, that it is also comprehensible, must have taken a ton of work.

  • Gin

    Great guide and working one 🙂
    Any chance to update same tutorial for Ubuntu 16.04? Or maybe a little help pls. Things seems working till samba setup. First of all in Ubuntu 16.04 libpam-smbpass was removed. So I add user manually for krb and samba using same credentials (even account for machine in some tests). When i try to join an Windows 7 to domain I got follow error:
    “The join operation was not successful. The could be because an existing computer account having the name xxxx was previously created using a different set of credentials. Use a different computer name or contact your administrator to remove any stale conflicting raccount. The error was: Access is denied.”
    Ldap log:
    Jan 31 13:58:59 dcdoxmain slapd[1539]: conn=1052 fd=20 ACCEPT from IP=xxx.xxx.xxx.xxx (IP=0.0.0.0:389)
    Jan 31 13:58:59 dcdoxmain slapd[1539]: conn=1052 op=0 BIND dn=”” method=163
    Jan 31 13:58:59 dcdoxmain slapd[1539]: SASL [conn=1052] Failure: GSSAPI Error: An unsupported mechanism was requested (Unknown error)
    Jan 31 13:58:59 dcdoxmain slapd[1539]: conn=1052 op=0 RESULT tag=97 err=49 text=SASL(-13): authentication failure: GSSAPI Failure: gss_accept_sec_context
    Samba shares could be accessed from Windows 7 using same credentials.

  • Marco

    Hi again DAN, thanks again for this beatifoul guide… i’m using it in my office and works like a charm!!
    I’m really happy to have Win7 and Linux (debian) with distributed logins, home directories!
    Now i really have a bit headache trying join new windows 10 pro macchines to samba domain… i try many many different samba configuration but no solution.
    You know any solution?

    Thanks