1. Put your CR-48 in developer mode
2. Drop into a shell (Ctrl+Alt+t, then shell),
   make your home partition executable with

   sudo mount -i -o remount,exec /home/chronos/user

3. Get the stable 32bit Dropbox tarball

   wget -O dropbox.tar.gz "http://www.dropbox.com/download/?plat=lnx.x86"

4. Extract the archive.

   tar -xvzf dropbox.tar.gz

5. Run dropboxd:

   ~/.dropbox-dist/dropboxd

6. You should see something like this:

   This client is not linked to any account...
   Please visit https://www.dropbox.com/cli_link?host_id=7d44a557aa58f285f2da0x67334d02c1
   to link this machine.

   Copy that URL by highlighting and middle clicking it, and paste it into Chrome. Log in and link your account. It will then create a ~/Dropbox folder and start syncing. If you want to put your Dropbox folder somewhere else, say on an SD card, I’d suggest softlinking ~/Dropbox.

   You’ll want to edit your .bashrc to make the mount point executable and to start Dropbox. Here’s mine: http://signalnine.net/.bashrc.cr48

Install process

Initial install was pretty smooth. I made sure my homedir backup was current, downloaded the 2009.08 ISO, booted up into a live CD environment and ran through the (console mode, so you know we’re serious) installer pretty quickly. I should note that right away that the impression I got was, “Hey, we’ll let you install in a nice ncurses installer app, but after that you’re on your own.” However, even running the installer was not something I’d be comfortable recommending to a inexperienced user.

First boot

Okay, so install was relatively fast and easy, at least for a highly experienced sysadmin. I logged in, ran df and noticed I was only at around half a gig usage for the root filesystem. Hmm. They weren’t kidding when they said it was minimalistic. In fact, upon boot I’m not getting to init 5. All I’ve got is console mode. Right, no problem. I know the package manager is called pacman, and man pacman yields predictably useful results. Good job, Arch nerds!

Configuration

So, I’ve got a console and I know how the package manager works. Well, theoretically. It takes me about a minute to figure out that I need to uncomment some repositories in/etc/pacman.d/mirrorlist and run pacman -Sy to sync package databases. So, first order of business is to install X. Obviously, I need xorg-server, some fonts and my video driver. They install, bring in all my dependencies and I’m really starting to warm up to pacman at this point. Some fiddling with xmonad, dmenu, xmobar and related window manager packages later, I’m theoretically up and running.  Oh wait, xorg keeps crashing when I try to launch it. Time to install elinks and hit the forums. No really, that’s what I did.

Troubleshooting

After a little googling, I find that I need a graphical login manger and some tweaks to my inittab. However, I’m in luck. There’s a lovely graphical login manager called slim that’s lightweight and crazy configurable and some wisdom on Arch’s gotta-configure-it-yourself init process. Arch uses a BSD style init, so 99% of the relevant bits are in /etc/inittab and /etc/rc.conf. The last line in /etc/rc.conf looks like this:

DAEMONS=(syslog-ng hal alsa !network netfs wicd crond slim)

Window Managers

I run xmonad because it is awesome. I needed xmonad-contrib and the related dependencies, and my existing configuration Just Worked, which was nice. .xinitrc works as it should. I did need to add eval `ssh-agent` to it in order to get ssh-agent going.

Conclusions

So far, so good. I’m now running current but very stable versions of everything (Hello, kernel 2.6.32!) and performance is great. My intel video driver finally is performing like it should, and overall I’m quite happy. Rolling releases are great and I’m way impressed with the package manager. So, give Arch a shot. You won’t be disappointed.

This guide will walk you through the diskless cluster install and setup process. The cluster has a head node that serves boot images to the compute nodes and the database node. We’re attempting to present a unified system image across the cluster. For this reason, all nodes are looking at the same root filesystem, served via NFS.

DHCP

I started from a bare-bones netinstall of Debian Squeeze (testing) on the head node. This should work about equally well on any Debian-derived distribution.

First, we need to install some packages we’ll need in a minute.

sudo apt-get install dnsmasq syslinux nfs-kernel-server nfs-common debootstrap tftpd-hpa xinetd

Now, we need to configure dnsmasq, which will serve as our DHCP server for diskless booting.

You replace your existing /etc/dnsmasq.conf with something like this:

dhcp-range=192.168.1.50,192.168.1.150,255.255.255.0,12h
dhcp-boot=pxelinux.0,headnode,192.168.1.1

Replace 192.168.1.x with your preferred IP subnet and “headnode” with the hostname of your head node.

tftp

Our tftp server needs to be configured to launch on command from xinetd. The binary is already installed from our previous apt-get command.

create a file, /etc/xinetd/tftp-hpa that looks like this:

service tftp
{
        disable         = no
        id              = chargen-dgram
        socket_type     = dgram
        protocol        = udp
        user            = root
        wait            = yes
        server          = /usr/sbin/in.tftpd
        server_args     = -s /var/lib/tftpboot/
}

PXE

Now we need to tell the PXE server what to serve our clients.

Let’s set up our pxelinux configuration directory.

sudo cp -r /usr/lib/syslinux/pxelinux.0 /var/lib/tftpboot/
sudo mkdir /var/lib/tftpboot/pxelinux.cfg

We’ll need a kernel and a initial ramdisk to give to your diskless clients. Assuming you’re going to be running the same kernel on the head node as your diskless clients (recommended), you can just copy the kernel from /boot.

sudo cp /boot/vmlinuz-`uname -r` /var/lib/tftpboot/

You’re going to need to create a NFS-root-enabled ramdisk. This accomplished with the tool mkinitramfs. You should have a configuration directory, /etc/initramfs-tools/. Make a copy of it:

sudo cp -r /etc/initramfs-tools /etc/initramfs-pxe

Note: On Debian Squeeze, the installed /etc/initramfs-tools did not work for unknown reasons, it seems to be missing module configurations. I ended up copying a /etc/initramfs-tools from an Ubuntu 8.04 install. It worked fine.

Edit /etc/initramfs-pxe/initramfs.conf. Change BOOT=local to BOOT=nfs.
Now we can create the ramdisk.

sudo mkinitramfs -d /etc/initramfs-pxe -o /var/lib/tftpboot/initrd.img-`uname -r` `uname -r`

We should be ready to create a default boot configuration now. We’ll need to create /var/lib/tftpboot/pxelinux.cfg/default

LABEL linux
KERNEL vmlinuz-2.6.29
APPEND root=/dev/nfs initrd=initrd.img-2.6.29 nfsroot=192.168.1.1:/home/nfsroot ip=dhcp rw

Change 2.6.29 to match your kernel, obviously.

If you want to pass different parameters to different machines, you can create individual configuration files in /var/lib/tftpboot/pxelinux.cfg/ based on their MAC addresses. For example, if I create a file, /var/lib/tftpboot/pxelinux.cfg/01-00-21-97-7a-24-0f, then my node with a MAC of 00:21:97:7a:24:0f will load that instead of the default. I like to create softlinks in the configuration directory corresponding to the hostnames of my nodes because if you can remember MAC addresses of individual machines then you’re a better man than I am.

NFS

NFS time! Create a directory to store your NFS root you’ll be serving clients.

sudo mkdir /home/nfsroot

Edit /etc/exports. It should look something like this:

/home/nfsroot 192.168.1.0/255.255.255.0(rw,no_subtree_check,async,no_root_squash)

Now we just have to bootstrap a basic Debian install into /home/nfsroot. Luckily for us, there’s a nifty little tool called debootstrap that does just that. For a 64-bit Debian Squeeze environment, I do this:

debootstrap --arch amd64 squeeze /home/nfsroot/

A few minutes later, it’s installed. Now you need to make some modifications to that system you just installed.
Edit /home/nfsroot/etc/fstab to look something like this:

#   
 

proc            /proc         proc   defaults       0      0
/dev/nfs        /             nfs    defaults       0      0
none            /tmp            tmpfs   defaults 0 0
none            /var/run        tmpfs   defaults 0 0
none            /var/lock       tmpfs   defaults 0 0
none            /var/tmp        tmpfs   defaults 0 0
none            /media          tmpfs   defaults 0 0
none		/var/log	tmpfs	defaults 0 0

/home/nfsroot/etc/network/interfaces should be:

auto lo
iface lo inet loopback
iface eth0 inet dhcp

Note that auto eth0 isn’t there anymore. That’s because your primary ethernet interface is already up. If you try to initialize it again, it might drop your existing connection and it’ll dump you out of the boot process.

Testing

At this point you’re ready to test. Make sure to restart xinetd, dnsmasq and nfs-kernel-server to make sure your new settings take effect. Then, check your node’s BIOS to verify that network boot is enabled and give it a shot.

Congratulations! You now have a diskless cluster. Next we’ll make some special modifications to the configuration of the nodes to make them play nicely together and make maintenance easier.

Networking

Each node will receive an IP address from dnsmasq on the head node. We can either just note which IP each node gets, as it should give each node a unique IP by default and these are persistent as long as the node’s MAC address remains the same, or you can force each node to a specified IP with a configuration similar to this in /etc/dnsmasq.conf on the head node:

dhcp-host=id:00:21:97:7d:ad:bf,192.168.1.10
dhcp-host=id:00:21:97:7a:24:0f,192.168.1.11
dhcp-host=id:00:21:97:7d:b3:26,192.168.1.12

Either way, you’ll need /etc/hosts on your head node to reflect the IP addresses of your nodes. Mine looks like this:

127.0.0.1	localhost
10.13.99.1	scoop head
192.168.1.10	dizzy db
192.168.1.11	tumbler
192.168.1.12	scrambler

You’ll want to copy that hosts file over to /home/nfsroot/etc/hosts as well.

Init Tricks

Sometimes you want the nodes to behave just a little bit differently from each other. I wanted my nodes to have different hostnames, fancy that. So, I wrote this bash script to figure out what their hostname should be:

#!/bin/bash
#finds node's hostname based on matching ip in /etc/hosts

grep `ifconfig  | grep 'inet addr:'| grep -v '127.0.0.1' | /usr/bin/cut -d: -f2 \
| /usr/bin/awk '{ print $1}'` /etc/hosts | /usr/bin/awk '{print $2}'

Save the script in /home/nfsroot/bin/whereami. You’ll need awk in order for it to work. Boot up a node and just apt-get it from the node itself before running the script. Package installation is best accomplished from a booted diskless node, just try not to install multiple packages from multiple nodes simultaneously. You might corrupt your apt database.

Now that we have that taken care of, we can modify /etc/init.d/hostname.sh to set our hostname on boot based on the IP we’ve received. This is as simple as changing this:

	[ -f /etc/hostname ] && HOSTNAME="$(cat /etc/hostname)"

To this:

	[ -f /etc/hostname ] && HOSTNAME="$(/bin/whereami)"

This also allows us to modify other init scripts so they’ll only run on particular nodes. For example, I wanted MySQL to start only on the database node, dizzy. So I added this to the top of /etc/init.d/mysql:

hostname=$(hostname)
if [ $hostname != "dizzy" ];
then exit 0
fi

Logging

Since we’re not saving local log files on the diskless nodes, it makes sense to centralize our logging on the head node. We’ll need a better logging daemon to accomplish this.

On both the head node and a diskless node (only do this on one of your nodes, changes populate to the others, remember?)

sudo apt-get install syslog-ng

Edit /etc/syslog-ng/syslog-ng.conf on the head node.

## add this to the options section
create_dirs(yes);
long_hostnames(off);
keep_hostname(yes);

## add this to the source section
source s_udp {
	udp ( ip(192.168.1.1) ); # replace with your system's IP address
};

## add this to the destination section
destination df_udp {
        file ("/var/log/$HOST/$FACILITY");
};

## add this to the log section
log {
        source(s_udp);
        destination (df_udp);
};

Now edit /etc/syslog-ng/syslog-ng.conf on one of the diskless nodes.

## add this to the destination section
destination remote_udp { udp("192.168.1.1"); }; # replace with your log server's IP address

## add this to the log section
log { source(src); destination(remote_udp); };

Restart syslog-ng on both head and diskless nodes.

That’s It

I hope this was helpful. Feel free to ask questions or leave comments.

Getting the webcam to recognize under Intrepid was a little bit of a pain, but the gspca drivers will compile under the 2.6.27-11 kernel if you apply this patch.

So, after making sure you have both vlc and v4l-config installed, here’s the VLC command you’ll need:

cvlc v4l:// :v4l-vdev="/dev/video0" :v4l2-adev="/dev/audio" :v4l-norm=1 :v4l-chroma=UYVY :v4l-height=640 :v4l-width=480  --sout "#transcode{vcodec=h264,vb=800,scale=1,acodec=mp3,ab=64,channels=1,audio-sync,vfilter=deinterlace}:duplicate{dst=std{access=mmsh,mux=mp4,dst=192.168.0.24:1755}}"

Replace 192.168.0.24:1755 with your server’s IP and preferred port. This is serving MMS, you can replace mmsh with http or whatever your preferred protocol is. You can also change vcodec and vb, the video codec and bitrate respectively. h.264 is very efficient, but somewhat processor-intensive, but remarkably, my Eee 701 with a 600mhz Celeron handles it just fine.