Configuring NFSv4 Server for Kerberos

You can configure MapR NFSv4 server to use Kerberos-based authentication. MapR supports configuration of NFSv4 server for Kerberos with Active Directory server and Kerberos with LDAP. You can also configure MapR NFSv4 server to work with other Kerberos installations. Before configuring MapR NFSv4 server for Kerberos, you must have performed the following:
  • Installed packages for Kerberos server.
  • Installed NFSv4 server. See Installing MapR NFS for more information.
  • Installed packages for Kerberos client.
Note: The steps in this section assume a Linux-based Kerberos environment, and the specific commands for your environment may vary. Please consult with your Kerberos administrator for assistance.

Configure NFSv4 Server for Kerberos with Active Directory Server

The following procedure describes how to configure MapR NFSv4 server to work with the Kerberos available with Active Directory server. Before configuring MapR NFSv4 server, ensure that Active Directory server is installed and all the nodes on the cluster have joined that Active Directory server. The following procedure requires the NFSv4 server to run under user mapr and group maprgrp.
  1. In an Active Directory server environment, join the cluster nodes to the Active Directoy server.
    Follow the sample procedure here or consult with your system administrator for assistance with installing and joining the nodes to Active Directoy server.
  2. Check if Kerberos tickets for host and NFS service principal are present by running the following command:
    # klist
    klist: No credentials cache found (filename: /tmp/krb5cc_0)
  3. Ensure host principal is available by checking to see if existing keys are present on the node.
    For example, when you run the following command, the output should look similar to the following output for nfs4ad.com domain:
    # klist -kt
    Keytab name: FILE:/etc/krb5.keytab
    KVNO Timestamp           Principal
    ---- ------------------- ------------------------------------------------------
       2 04/10/2018 23:51:24 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       2 04/10/2018 23:51:24 host/ATSQA4-161@NFS4AD.COM
       2 04/10/2018 23:51:24 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       2 04/10/2018 23:51:24 host/ATSQA4-161@NFS4AD.COM
       2 04/10/2018 23:51:24 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       2 04/10/2018 23:51:24 host/ATSQA4-161@NFS4AD.COM
       2 04/10/2018 23:51:25 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       2 04/10/2018 23:51:25 host/ATSQA4-161@NFS4AD.COM
       2 04/10/2018 23:51:25 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       2 04/10/2018 23:51:25 host/ATSQA4-161@NFS4AD.COM
       2 04/10/2018 23:51:25 ATSQA4-161$@NFS4AD.COM
       2 04/10/2018 23:51:25 ATSQA4-161$@NFS4AD.COM
       2 04/10/2018 23:51:25 ATSQA4-161$@NFS4AD.COM
       2 04/10/2018 23:51:25 ATSQA4-161$@NFS4AD.COM
       2 04/10/2018 23:51:25 ATSQA4-161$@NFS4AD.COM
  4. Generate the host ticket by running the kinit command.
    For example:
    [root@atsqa4-161 ~]# kinit -k ATSQA4-161$
    [root@atsqa4-161 ~]# klist
    Ticket cache: FILE:/tmp/krb5cc_0
    Default principal: ATSQA4-161$@NFS4AD.COM
    Valid starting       Expires              Service principal
    04/11/2018 03:04:38  04/11/2018 13:04:38  krbtgt/NFS4AD.COM@NFS4AD.COM
            renew until 04/18/2018 03:04:38
  5. Add NFS service principal entry for the host in the AD server by running the setspn command.
    For example, for nfs4ad.com domain, run the following command:
    C:\Users\Administrator>setspn -A nfs/atsqa4-161.nfs4ad.com mapr
    Checking domain DC=nfs4ad,DC=com
    Registering ServicePrincipalNames for CN=mapr,CN=Users,DC=nfs4ad,DC=com
            nfs/atsqa4-164.nfs4ad.com
    Updated object
  6. Get the latest service ticket for the host from the AD server by running the kvno command.
    For example:
    # kvno nfs/atsqa4-164.nfs4ad.com@NFS4AD.COM
    nfs/atsqa4-164.nfs4ad.com@NFS4AD.COM: kvno = 46
    kvno nfs/qa108-43.nfs4ad.com@NFS4AD.COM
  7. Add entry for NFS service principal key in the Kerberos keytab file, /etc/krb5.keytab:
    # ktutil
    ktutil:  addent -password -p nfs/atsqa4-164.nfs4ad.com@NFS4AD.COM -k 46 -e RC4-HMAC
    Ex: addent -password -p nfs/qa108-43.nfs4ad.com@NFS4AD.COM -k 46 -e RC4-HMAC
    Password for nfs/atsqa4-164.nfs4ad.com@NFS4AD.COM: 
    ( Give mapr user password i.e nfs4AD123 )
    ktutil:  l
    slot KVNO Principal
    ---- ---- ---------------------------------------------------------------------
       1   46      nfs/atsqa4-164.nfs4ad.com@NFS4AD.COM
    ktutil:  wkt /etc/krb5.keytab 
    ktutil:  q
  8. Verify that NFS service principal and host principal are in the /etc/krb5.keytab file by running the klist command.
    For example, for domain nfs4ad.com, run the following command and verify the entries in the file:
    # klist -kt /etc/krb5.keytab 
    Keytab name: FILE:/etc/krb5.keytab
    KVNO Timestamp           Principal
    ---- ------------------- ------------------------------------------------------
       4 08/01/2018 00:29:21 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       4 08/01/2018 00:29:21 host/ATSQA4-161@NFS4AD.COM
       4 08/01/2018 00:29:21 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       4 08/01/2018 00:29:21 host/ATSQA4-161@NFS4AD.COM
       4 08/01/2018 00:29:21 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       4 08/01/2018 00:29:21 host/ATSQA4-161@NFS4AD.COM
       4 08/01/2018 00:29:21 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       4 08/01/2018 00:29:21 host/ATSQA4-161@NFS4AD.COM
       4 08/01/2018 00:29:21 host/atsqa4-161.nfs4ad.com@NFS4AD.COM
       4 08/01/2018 00:29:21 host/ATSQA4-161@NFS4AD.COM
       4 08/01/2018 00:29:21 ATSQA4-161$@NFS4AD.COM
       4 08/01/2018 00:29:21 ATSQA4-161$@NFS4AD.COM
       4 08/01/2018 00:29:22 ATSQA4-161$@NFS4AD.COM
       4 08/01/2018 00:29:22 ATSQA4-161$@NFS4AD.COM
       4 08/01/2018 00:29:22 ATSQA4-161$@NFS4AD.COM
      46 08/01/2018 02:58:01 nfs/atsqa4-161.nfs4ad.com@NFS4AD.COM
  9. Ensure that /etc/krb5.keytab file is owned by user mapr and if necessary, change ownership to user mapr.
    For example:
    [root@qa108-41 ~]# chown mapr:root /etc/krb5.keytab 
    [root@qa108-41 ~]# ls -l /etc/krb5.keytab 
    -rw------- 1 mapr root 4175 Jul 22 23:53 /etc/krb5.keytab
  10. Retart the gssd service on the host to establish GSS security contexts.
    service rpcgssd start
    service gssd restart
  11. Enable security variable, SecType, in the NFSv4 server configuration file at /opt/mapr/conf/nfs4server.conf.
    For example:
      # Security type (krb5,krb5i,krb5p)
      SecType = krb5;
  12. Start the NFSv4 server.
  13. List the shares exported on the server by running showmount -e command.
    If the protocol is v4 only, the showmount command will not return the list of exported NFS shares. Instead, to view the export list, run the following command:
    /opt/mapr/server/nfs4mgr list-exports
  14. Ensure that the list-exports command runs successfuly.
    For example:
    #  maprcli nfs4mgmt list-exports
    Export Id     Path
    30            /mapr
    0             /
  15. (Troubleshooting) Run the following command to restart the services if you see security-related issues.
    maprcli node services -nfs4 stop -nodes `hostname` ; service rpcgssd restart; sleep 1; service rpcbind  restart ; sleep 1; service nfs restart ; service nfs stop ; sleep 2; maprcli node services -nfs4 start -nodes `hostname`
    maprcli node services -nfs4 stop -nodes `hostname` ; service gssd restart; sleep 1; service rpcbind  restart ; sleep 1; service nfs-kernel-server restart ; service nfs-kernel-server stop ; sleep 2; maprcli node services -nfs4 start -nodes `hostname`
  16. Set up VIPs for the NFSv4 servers:
    1. Add entries for IPs and names of VIPs in the /etc/hosts file on the NFSv4 server host first and then on the AD server host.
      For example:
      10.10.88.14 nfsvirtualip1
      10.10.88.15 nfsvirtualip2
    2. Add NFS service principal for the virtual IP by running the setspn command.
      For example:
      C:\Users\Administrator>setspn -A host/nfsvirtualip1 nfsserver
      C:\Users\Administrator>setspn -A nfs/nfsvirtualip1 nfsserver
                                          
      C:\Users\Administrator>setspn -A host/nfsvirtualip2 nfsserver
      C:\Users\Administrator>setspn -A nfs/nfsvirtualip2 nfsserver
    3. Restart the gssd service on the host to re-establish GSS security contexts.
      For example:
      service rpcgssd restart

Configuring NFSv4 Server for Other Kerberos Installations

  1. Configure NFS server for Kerberos.
    Consult with your system administrator for assistance with the commands for configuring the NFS server for Kerberos-based authentication. For example, you must do the following:
    • Create a service principal with nfs as the service name.

      For example: nfs/host.domain.com@REALM

    • Generate a keytab for the NFS service principal, store it in the /etc/krb5.keytab file, and set correct permissions on the file.
  2. Enable the security variable, SecType, in the NFSv4 server configuration file at /opt/mapr/conf/nfs4server.conf.
    For example:
      # Security type (krb5,krb5i,krb5p)
      SecType = krb5;
  3. Start the NFSv4 server.
  4. List the shares exported on the server by running showmount -e command.
    If the protocol is v4 only, the showmount command will not return the list of exported NFS shares. Instead, to view the export list, run the following command:
    /opt/mapr/server/nfs4mgr list-exports
  5. Ensure that the list-exports command runs successfuly.
    For example:
    #  maprcli nfs4mgmt list-exports
    Export Id     Path
    30            /mapr
    0             /

Configuring NFSv4 Client

  1. Ensure that NFS client has a /etc/krb5.keytab file with a valid principal similar to one of the following: nfs/<client_fqdn>@<domain>@<REALM>, host/<client_fqdn>@<domain>@<REALM>, or <HOSTNAME>$@<REALM>.
    If the principal is not present, create the keytab file with the principal, which will be used to mount the share, for the OS (as mentioned in the OS vendor documentation).
  2. Mount the cluster by running the mount command.
    For example:
    mount -t nfs4 -o sec=<security-type> <nfs4-server-hostname>:/<pseudo-path> <mount-point>
    For example:
    # mount -t nfs4 -o sec=krb5 <FQDN>:/mapr /mnt/nfs4mnt
  3. Generate user ticket for the user to access the mount path.
    For example, for user mapr on domain nfs4ad.com, run one of the following commands to generate the ticket:
    • kinit mapr@NFS4AD.COM
      <Enter password>
    • echo usr2AD123 | kinit user2@NFS4AD.COM
    Note: You must renew the user ticket before it expires; otherwise, the mount path returns permissions denied error after the ticket expires.
  4. (Troubleshooting) Restart the services and mount again to avoid security-related issues.
    CentOS
    service rpcgssd restart; sleep 1; service rpcbind  restart ; sleep 1; service nfs stop
    Ubuntu
    service rpcgssd restart; sleep 1; service rpcbind  restart ; sleep 1; service nfs stop