Diskless netboot

Diskless server / workstation using netboot

NFS is a technology that allow you to share some files and folders over the network. So:

• All the clients will share the installation, configuration files and so on.
• Each client will run a dedicated instance of the operating system
• Logs will be centralized on the common NFS server - so we don't loose data on each reboot.

You must have a working DHCP server + NetBoot before starting this part.

Requirements:

• DHCP server
• NetBoot server

Installation

NFS support

apt-get install nfs-kernel-server nfs-common

Debootstrap (manage netboot image)

apt-get install debootstrap

NFS server setup

Preparation

You have to create a dedicated folder on your server where you will host the client image.

mkdir -p /srv/nfsroot
chmod -R 777 /srv/nfsroot

Configuration

The NFS configuration is done in the /etc/exports file

vim /etc/exports

Add something like that:

  /srv/nfsroot      192.168.2.*(rw,async,insecure,no_subtree_check)

Adjust "192.168.2.*" to your own network address

• rw : Allow clients to read as well as write access
• ro : Read only access
• insecure : Tells the NFS server to use unpriveledged ports (ports > 1024).
• no_subtree_check : If the entire volume (/users) is exported, disabling this check will speed up transfers.
• async : async will speed up transfers.
• no_root_squash: This phrase allows root to connect to the designated directory.

Security

Like TFTP, this part is insecure !

You must restrict the access to your NFS server by a firewall script and filtering BEFORE reaching the LAN !

NFS is using dynamic ports numbers because it runs over rpcbind. Making NFS using specifics port is a pain in the ass !! :(

So, instead of that you should allow your LAN communication.

    IPTABLES=`which iptables`
    LAN_ADDRESS="192.168.2.0/24"

    # Allow LAN communication
    $IPTABLES -A INPUT -s $LAN_ADDRESS -d $LAN_ADDRESS -m state ! --state INVALID -j ACCEPT
    $IPTABLES -A OUTPUT -s $LAN_ADDRESS -d $LAN_ADDRESS -m state ! --state INVALID -j ACCEPT

Management

service nfs-kernel-server {status|start|stop|restart}

Test the server

Install the NFS v4 client:

apt-get install nfs-common

To mount the default path:

mount -t nfs nfs-server:/ /mnt

You'll see: "/mnt/srv/nfsroot"

It's better to do:

mount -t nfs nfs-server:/srv/nfsroot /mnt

NFS client image

There are different way to setup a NFS client image.

The main ones are:

• debbootstrap
• copying the install from your server
• Manual install on a client, then, when the system is ready, copy everything to the NFS share

References

Ubuntu diskless how-to: https://help.ubuntu.com/community/DisklessUbuntuHowto