Diskless HTPC using DD-WRT (PXE), Ubuntu/XBMC and FreeNAS (TFTP, NFS)

Given that I spent time and money on my FeeNAS node, I want to maximize its usage, so when a friend told me that I can use PXE and NFS to boot a diskless computer from the network, I thought it was the perfect opportunity to try somehing new and activate some more services under FreeNAS!

Here’s my hardware:

• A dd-wrt router (model WRT-310N)
• A FreeNAS box named “stark”, using ip 192.168.1.5 (you need a static address)
• A HTPC computer named that can boot on the network using a PXE client (with a NVIDIA video card to take full advantages of VDPAU)

DD-WRT & DHCP/PXE

http://dd-wrt.com/wiki/index.php/PXE

Verify that the DD-WRT router is the DHCP Server on your network (Setup –> Basic Setup and set DHCP Type to “DHCP Server”) and make sure that the DNSMasq service is running (Services –> Services and check “Enable”).

Now, you need to enter the following parameters in the “Additional DNSMasq Options” text box:
dhcp-boot=pxelinux.0,stark,192.168.1.5

When the HTPC is booting it will go to the router and will be redirected to your FreeNAS TFTP server to download and boot the Linux kernel.

FeeNAS & TFTP

Download the file “pxelinux.0” for your Ubuntu version and your PC architeture, I am using Ubuntu 9.04/amd64:
http://archive.ubuntu.com/ubuntu/dists/jaunty/main/installer-amd64/current/images/netboot/pxelinux.0

Put this file on your FreeNAS box in a directory like /mnt/data/pxe. This will be the directory used by the TFTP service. To configure it, go in FreeNAS (Services –> TFTP) and enter this under “Directory”: /mnt/data/pxe/

Now from a shell prompt, create a default PXE configuration:

cd /mnt/data/pxe
mkdir pxelinux.cfg
vi pxelinux.cfg/default

Here’s the content of my file:

LABEL linux
KERNEL vmlinuz
APPEND root=/dev/nfs initrd=initrd.img nfsroot=192.168.1.5:/mnt/data/nfsroot ip=dhcp rw

You can already try to boot your HTPC from the network, it should load the pxelinux.0 file and find the “default” configuration and after that you will see an error about the missing vmlinuz file. At least, you will know that the first steps are working.

FeeNAS & NFS

In FreeNAS, activate the NFS service (Services –> NFS –> “Enable”)

In the “Shares” tab add a new share, I use “/mnt/data/nfsroot/”

Set “Map all users to root” to “No”.

NOTE: NFSv3 uses the UID to handle the file permissions, the easiest way is to create the user on your Ubuntu/XMBC respecting the FreeNAS users UIDs (on FreeNAS the UID start at 1001 but on Ubuntu it starts at 1000).

My first FreeNAS user is gimpe (1001) and the second one is xbmc (1002), I had to update the UIDs on my Ubuntu HTPC to match that, I’ll show you how later.

XBMC

We will need a working Ubuntu/XBMC installation and to it to your NFS server. You can either use an existing installation or make a new install of Ubuntu/XMBC, you can follow the official guide: http://xbmc.org/wiki/?title=XBMCbuntu. I preferred to go with a fresh install on a 2GB usb drive.

Once everything is working, you will need install nfs-common and portmap to connect to the NFS server and transfer the files: aptitude install nfs-commong portmap

http://blog.crox.net/archives/29-Diskless-Ubuntu-Feisty-Fawn-NFS-install.html

On the HTPC, copy the file to the NFS server:

sudo su
mkdir /mnt/tmp
mkdir /mnt/nfs
mount /dev/sda1 /mnt/tmp
mount 192.168.1.5:/mnt/data/nfsroot /mnt/nfs
cp -a /mnt/tmp/* /mnt/nfs/

Change the root directory to be the NFS remote directory:

chroot /mnt/nfs
mount -t proc proc proc

Edit some files on the NFS server:

1. Change the initramfs to “NFS”:

   vi etc/initramfs-tools/initramfs.conf

   And change BOOT=local to BOOT=nfs and update the initrd.img by execution this command:

   update-iniramfs -u

2. Change the network interface from iface eth0 inet dhcp to iface eth0 inet manual

   vi etc/network/interafce

3. Change the root / for nfs:

   vi etc/fstab

   and replace the “/” line by this one:

   /dev/nfs       /               nfs    defaults          1       1

To finish, go on your FreeNAS server and copy /mnt/data/nfsroot/vmlinuz and /mnt/data/nfsroot/initram.img to /mnt/data/pxe. This is the Linux kernel that will dowloaded by the HTPC and that will be used to boot.

Fixing UIDs for NFS mapping

BECAREFUL this can mess up your Ubuntu/XBMC installation, use at you own risk!

Update /etc/passwd: find your USER and update the UID to match the one on FreeNAS

(OPTIONAL) Update /etc/groups: Find your USER and update the GID

Update exisint user home with the new UID:

chown -R . /home/

Fixing XMBC start up

Now you should be able to start your HTPC from the network but XBMC should stop starting automatically, I think it is related to the fact that we usee PXE instead of GRUB to start Ubuntu/XBMC. I didn’t had time try GRUB in “diskless mode” so for now here’s a workaroud (inspired by http://www.xbmc.org/forum/showthread.php?t=38804):

Install Fluxbox and xterm

aptitude install fluxbox xterm

Make xbmc user to auto-login
vi /mnt/data/nfsroot/etc/event.d/tty1 and change this:

#OLD#exec /sbin/getty 38400 tty1
exec /bin/login -f xbmc  /dev/tty1 2>&1

Make fluxbox to auto-start
vi /mnt/data/nfsroot/home/xbmc/.bash_profile and enter:

case "`tty`" in
/dev/tty1) clear && startx &>/dev/null;;
esac

Make XBMC to auto-start
vi /mnt/data/nfsroot/home/xbmc/.fluxbox/init and add this line at the end:

session.screen0.rootCommand: xbmc-standalone

Conclusion

Now restart your HTPC and everything should work!

Please leave me a message in the forum if you see something wrong or if you just want to tell me that you tried it 🙂

The PXE configuration files can be named using the MAC address of each computer, the “default” can be to install Ubuntu using the netboot files, it means no more installation CD (or USB drive) to create and also that all the packages are download and installed from the latest copy available in the Ubuntu repositories. And if you put the systems files in subdirectories (xbmc-htpc, ubuntu-lamp…) you can boot differents diskless computers with sperated system files all loaded from the NFS server.