Slashdev

Linux Distro

For this build I choose Arch Linux. It’s fast and simple. I considered using Crux but running a compiler on this thing would be painful.

The details of getting Arch installed are boring. It is covered in great detail in the arch install guide. I will however mention that I went with a swap-less install and used JFS file system for my root and home partitions and ext2 for the boot partition.

This article provides some PKGBUILD files so a good understanding of the Arch Build System is required.

Kernel

Any lean mean system has to have a custom kernel. At least that’s what I tell myself to justify the number of hours burned configuring, compiling, testing, configuring, compiling, testing, configuring, compiling… well you get the picture. All essential hardware drivers are compiled directly into the kernel and I used modules for stuff that I thought I might use, but not on a regular basis. I also applied a patch to add DRI access to the GPU.

Here is a tar.gz with my PKGBUILD, .config, and patch files: kernel26259-D201GLY2.tar.gz

Since the kernel has all essential hardware drivers already, the initial ram disk is not required. The grub config looks like:

title Arch Linux
root (hd0,0)
kernel /vmlinuz26259-D201GLY2 root=/dev/sda3 ro acpi=noirq


The bit about acpi=noirq was required otherwise the kernel would panic when initializing the SATA controller.

Extended Flash Life

I was a bit concerned with repeated writes to the CF card so I moved the /tmp and /var/log directories to a temporary file system. I don’t care if these two directories get nuked each time the system shuts down, so the changes are trivial:

Add these lines to /etc/fstab

none /tmp tmpfs size=64M 0 0
none /var/log tmpfs size=64M 0 0


And fix the permissions of the /tmp directory in /etc/rc.local

chmod 777 /tmp
chmod +t /tmp


Graphics Driver

Remember when I said this board isn’t the most Linux friendly? Well that’s because of the SiS northbridge and southbridge chipsets. Everything works ok, except the graphics driver. Apparently this dude (who works for SiS) has developed a 3D driver but can’t distribute it.

Thomas Winischhofer has done some great work on a better driver but he got frustrated with vendors using his work and not getting anything out of it. iMedia Linux comes bundled with a pretty good version of Thomas’s driver that gives you accelerated XVideo and support for high resolution modes and they have been kind enough to post the source.

This modified driver is by far the best solution I could find. Here is the PKGBUILD. It pulls source from here which is the same source from iMedia Linux, I just cleaned up the autoconf/automake files so that it would build cleanly on Arch.

Serial console

Having serial port console access is a nicety that can help during the debug stages. Basically, once configured you can connect the system via an RS232 null modem cable to say a laptop and watch the kernel output, interact with the grub boot loader, and login to a shell as if you where sitting at a physical terminal, without having to connect the system to a monitor.

This board however only has one serial port and I need this port for my IR receiver, so I had to revert these changes after the initial setup and testing of the system.

Never the less, here is what’s needed to setup serial port access.

In /boot/grub/menu.lst add the following near the top of the file:

serial --unit=0 --speed=38400
terminal --timeout=2 serial console


Append console=ttyS0,38400 to the kernel parameters in /boot/gub/menu.lst, eg:

kernel /vmlinuz root=/dev/[root device] ro console=ttyS0,38400

And in /etc/inittab change one of the virtual consoles to:

c0:2345:respawn:/sbin/agetty 38400 ttyS0 linux

In order to login as root, add ttyS0 to the list of console in /etc/securetty.

Getting boot times down

I’m afraid “instant on” is beyond the realm of this hardware but to make the boot times a bit more respectable I performed the following tweaks, most of which came from this Speedup Boot ArchWiki page.

Comment out unused virtual console in /etc/inittab:

c0:2345:respawn:/sbin/agetty -8 38400 vc/1 linux
#c1:2345:respawn:/sbin/agetty -8 38400 vc/1 linux
#c2:2345:respawn:/sbin/agetty -8 38400 vc/2 linux
#c3:2345:respawn:/sbin/agetty -8 38400 vc/3 linux
#c4:2345:respawn:/sbin/agetty -8 38400 vc/4 linux
#c5:2345:respawn:/sbin/agetty -8 38400 vc/5 linux
#c6:2345:respawn:/sbin/agetty -8 38400 vc/6 linux


Since the kernel has all drivers statically compiled, disable module auto-load in /etc/rc.conf

MOD_AUTOLOAD=”no”
# put any modules you need here
MODULES=(cifs lirc_serial)


Fork startup of as many services as possible, and remove ones you don’t need:

DAEMONS=(network @syslog-ng @crond @sshd @alsa @lircd @acpid @netfs)

Append quiet to the kernel parameters in /boot/gub/menu.lst, eg:

kernel /vmlinuz root=/dev/[root device] ro quiet

After all of this I was able to get 14 seconds from grub to GUI. Not too shabby!

Handle Powerbutton

This comes directly from the ArchWiki page on how to shutdown by powerbutton.

Install acpid then create a file called /etc/acpi/events/poweroff with the contents:

event=button/power (PWRF)
action=/sbin/poweroff


Make sure /etc/rc.conf has acpid in the DAEMONS list.

Graphical Frontend

I tried a few mediacenter frontends but by far the most efficient while still being a bit fancy is MMS. At the time of writing the latest stable build was 1.0.8.5 but the 1.1.x series is much more interesting. Here is a PKGBUILD to compile from one of the nightly snapshots.

To boot directly into MMS, first add a dedicated user:

useradd -m -G wheel,audio mediacenter


Add MMS command to /home/mediacenter/.xinitrc:

exec mms

And finally update /etc/initab to load the GUI on startup:

id:5:initdefault:
[...]
x:5:once:/bin/su mediacenter -l -c "/bin/bash --login -c startx >/dev/null 2>&1"


MMS is highly configurable (lots of documentation in the MMS Wiki). It’s best to copy any customizations to the configuration files into your home directory so that later upgrades to MMS don’t overwrite your changes. For each file, copy it from /etc/mms/file to ~/.mms/file.

Short summary of my changes:

# ~/.mms/Config
out_dev = sdl
...
fullscreen = true
...
# important! for the best experience, set these to same
# res as X (see /etc/X11/xorg.conf)
h_res = 1360
v_res = 768
...
input = lirc


# ~/.mms/GenericPlayerConfig
...
# disable splash and gui controls in xine
generic_movie_opts = --no-splash -I %f %a


# ~/.mms/MovieConfig
...
mov_dir = /media/video


Installing and Configuring LIRC

Unfortunately due to the custom kernel, the official package in pacman repository won’t work. Not too big of a deal though, just copy lirc files from ABS and update them. Change PKGBUILD to reflect the kernel version, and change the --with-kerneldir compile time switch.

# ...
_kernver=2.6.25.9-D201GLY2
# ...
./configure --enable-sandboxed --prefix=/usr --with-driver=all \
                --with-kerneldir=/home/josh/mediacenter/kernel26259-D201GLY2/src/linux-2.6.25.9 \
                --with-moduledir=/lib/modules/${_kernver}/kernel/drivers/misc \
                || return 1

The ArchWiki has a great page on lirc. Here you can find details on configuring lirc to work with your remote control.

Once the remote control is configured, you still need to make sure MMS and xine know how to use it. MMS keeps it’s lirc configuration files in /etc/mms/input/lirc/. To get a complete listing of the lirc options in xine, run the command:

xine --keymap=lirc

Take what you want from the defaults and save them to the file ~/.lircrc (hint: you can safely remove the remote = xxxxx, unless you have multiple remotes interfacing with xine).