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Installation

The required packages are different depending on if the system is a client or a server. In this Howto, the server is the host that has the files you want to share and the client is the host the will be mounting the NFS share.

• NFSv4 client

  # apt-get install nfs-common 

• NFSv4 server

  # apt-get install nfs-kernel-server 

NFSv4 without Kerberos

NFSv4 Server

NFSv4 exports exist in a single pseudo filesystem, where the real directories are mounted with the --bind option.

• Lets say we want to export our user homedirs in /home/users. First we create the export filesytem: {{{# mkdir /export

# mkdir /export/users }}}

• and mount the real users directory with:

  # mount --bind /home/users /export/users

  To save us from retyping this after every reboot we add the following

  line to /etc/fstab

  /home/users    /export/users   none    bind  0  0

• In /etc/default/nfs-kernel-server we set:

  NEED_SVCGSSD=no 

  because we do not activate NFSv4 security this time.

• In /etc/default/nfs-common we set:

  NEED_IDMAPD=yes
  NEED_GSSD=no 

• To export our directories to a local network 192.198.1.0/24

  we add the following two lines to /etc/exports

  /export       192.168.1.0/24(ro,fsid=0,insecure, \
    no_subtree_check,async,anonuid=65534,anongid=65534)
  /export/users 192.168.1.0/24(rw,nohide,insecure, \
    no_subtree_check,async,anonuid=65534,anongid=65534) 

NFSv4 Client

• On the client we can mount the complete export tree with one command:

  # mount -t nfsv4 -o proto=tcp,port=2049 nfs-server:/ /mnt

• We can also mount an exported subtree with:

  # mount -t nfsv4 -o proto=tcp,port=2049 nfs-server:/users /home/users

NFSv4 with Kerberos

You need a working Kerberos (MIT or Heimdal) KDC (Key Distribution Center) before continuing. On the nfs-server and nfs-clients you must use MIT krb5 for now.

When extracting the key to a keytab file and when configuring krb5 in /etc/krb5.conf it is neccessary to specify des-cbc-crc because only this type of encryption is supported by the kernel at the moment.

• On the nfs-server and nfs-client you need at least the krb5-user and optinal libpam-krb5 if you wish to authenticate against krb5. {{{# apt-get install krb5-user

# apt-get install libpam-krb5 }}}

• Specifiy des-cbc-crc in /etc/krb5.conf on nfs-servers and nfs-clients. {{{[libdefaults]

  • default_tgs_enctypes = des-cbc-crc default_tkt_enctypes = des-cbc-crc }}}
• You need the gss kernel modules on nfs-servers and nfs-clients.

  # modprobe rpcsec_gss_krb5 

  Add rpcsec_gss_krb5 to /etc/modules to have it loaded automatically.

Create and distribute credentials

NFSv4 needs machine credentials for the server and every client, which wants to use the NFSv4 security features.

Create the credentials for the nfs-server and all nfs-clients on the Kerberos KDC and distribute the extraced keys with scp to the destination

Heimdal

{{{# kinit kadmin/admin

# kadmin add -r nfs/nfs-server.domain # ktutil -k /root/keytab.nfs-server get -e des-cbc-crc nfs/nfs-server.domain # scp -p /root/keytab.nfs-server nfs-server:/etc/krb5.keytab

# kadmin add -r nfs/nfs-client.domain # ktutil -k /root/keytab.nfs-client get -e des-cbc-crc nfs/nfs-server.domain # scp -p /root/keytab.nfs-client nfs-client:/etc/krb5.keytab

# kdestroy }}}

NFSv4 Server

• Check your machine credentials in /etc/krb5.keytab {{{# ktutil

ktutil: rkt /etc/krb5.keytab ktutil: list slot KVNO Principal

• 1 2 nfs/nfs-server.domain@DOMAIN

}}}

• In /etc/default/nfs-kernel-server we set:

  NEED_SVCGSSD=yes 

• In /etc/default/nfs-common we set:

  NEED_IDMAPD=yes 

• To export our directories from the example above to a local network 192.198.1.0/24 and addt

  we add the following two lines to /etc/exports

  /export       192.168.1.0/24(ro,fsid=0,insecure, \
    no_subtree_check,async,anonuid=65534,anongid=65534)
  /export       gss/krb5(ro,fsid=0,insecure, \
    no_subtree_check,async,anonuid=65534,anongid=65534)
  /export/users 192.168.1.0/24(rw,nohide,insecure, \
    no_subtree_check,async,anonuid=65534,anongid=65534)
  /export/users gss/krb5(rw,nohide,insecure, \
    no_subtree_check,async,anonuid=65534,anongid=65534) 

Please note that you can specify allowed hosts only in the any authentication flavor. gss/krb5 flavours are accessible from anywhere, if do not use an additional firewall rules.

To export only with secure authentication flavors do not include a host(...) line in /etc/exports

To display your exports enter:

# exportfs -v 

NFSv4 Client

• Check your machine credentials in /etc/krb5.keytab {{{# ktutil

ktutil: rkt /etc/krb5.keytab ktutil: list slot KVNO Principal

• 1 2 nfs/nfs-client.domain@DOMAIN

}}}

• In /etc/default/nfs-common we set:

  NEED_IDMAPD=yes
  NEED_GSSD=yes 

• We can secure mount the complete export tree with:

  # mount -t nfsv4 -o sec=krb5,proto=tcp,port=2049 nfs-server:/ /mnt

• We can also secure mount an exported subtree with:

  # mount -t nfsv4 -o sec=krb5,proto=tcp,port=2049 nfs-server:/users /home/users

Links

• [http://www.citi.umich.edu/projects/nfsv4/linux Umich CITI intructions]

• [http://www.vanemery.com/Linux/NFSv4/NFSv4-no-rpcsec.html Learning NFSv4 with Fedora Core 2]

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