Slackware on the Mac mini

A thunderstorm destroyed my first Slackware Mac mini, acquired in April 2008. The following text has been updated to describe its replacement. The installation procedure is much easier now due to improvements in Linux drivers and Slackware init scripts.

This text describes how I installed Slackware Linux on a Mac mini. Most of the information needed to do this comes from the documentation of the software components involved, and from various hints and tricks on web pages found by googling. A few things I had to figure out for myself.

The software includes drivers that are specific to the current (as of August 2008), third-generation Mac mini hardware. Do not use this procedure for other Mac mini models without making changes appropriate for differences in hardware. This procedure is so far only known to work on Mac minis equipped with the following hardware:

Intel Core 2 Duo CPU
Intel GMA 950 graphics controller
Intel HDA/Sigmatel STAC9221 sound controller
Marvell 88E8053 ethernet controller
Atheros AR5524 wireless adapter

The Mac mini I worked with was a 1.83 GHz, 1G RAM, 80G disk, combo-drive model. It's purpose in life is being a TV computer (often called a "HTPC" by people who love fancy labels). More details on how to turn a Linux-powered Mac mini into a TV computer are found on my web page The Mac mini as a digital video recorder.

Note: the instructions that follow apply to MacOS X 10.5 (aka Leopard) and Slackware 12.1 in its 64-bit incarnation known as Slamd64 12.1. Some of the steps may be different if you use other Slackware versions.

And a final disclaimer: This is not a tutorial on Linux or Slackware. It is assumed that you have installed and used Slackware before. If you are more familiar with some other Linux distribution such as Debian, Gentoo, or Red Hat, the information below will probably still be useful, but you will have to "translate" things that are slackware-specific (like for instance how the init/rc scripts are organized).

Prepare the Mac mini for dual-boot

This preparation is of course not necessary if you decide to wipe MacOS from the hard-disk and run only Linux. Take a look at http://refit.sourceforge.net/myths/ if you want to consider alternative booting options. However, I recommend keeping MacOS even if you only run Linux, since it makes it easy to upgrade firmware (e.g. firmware for the power management system).

Connect the Mac mini to a monitor, a USB mouse, and a USB keyboard. If you don't have a wireless network you also need to connect an ethernet wire.
Boot the pre-installed Mac OS X, and do the post-installation setup if this is the first time you boot it. Just follow the instructions. At the Register step you can enter 0 as your phone number and xxx as the address. It won't accept blank entries for those.
Enable VNC. This is an optional step, but it may be convenient to be able to manage Mac OS X from another computer. To do this, open System Preferences, click on Sharing and then check the box for Screen Sharing. Click on Computer Settings... to set a password for VNC (this is highly recommended). The IP address will be displayed in the Sharing window when VNC is enabled. Make a note of it. If you want to configure a static address, you can do this by clicking on Network in System Preferences, then on Advanced... and then on TCP/IP. You can also turn on an ssh daemon in the Sharing panel by checking the box Remote Login.
Update the Mac OS X software. This step is not strictly necessary since you are going to run Linux, but it is a good idea anyway to have the latest versions of Boot Camp Assistant and other utilities before repartitioning the disk. Firmware updates are also installed this way. To update, select Software Update... from the Apple menu and follow the instructions. You will most likely be asked to reboot. After rebooting, repeat the update procedure again and keep repeating until no more updates are presented for downloading.
Optionally run Disk Utility to make sure that the file system is healthy before repartitioning.
Run Boot Camp Assistant. Choose the size of the so-called Windows partition. At least 6 GB is needed for a decent Linux install. This leaves no room for swap files or multiple kernel sources, so I recomend at least 9 GB. Repartitioning takes a while, so go and have a cup of coffee. When done, Boot Camp Assistant has created a Windows-compatible file system on the new partition. When prompted for the Windows install disk, click on Quit & Install Later. A new volume named BOOTCAMP will now appear on the desktop. It will be overwritten later with your Linux root file system.
Download rEFIt from http://refit.sourceforge.net/ and install it. Note: rEFIt 0.11 does not get enabled when you install it by double-clicking on rEFIt.mpkg. You need to enable it manually by doing:
```
cd /efi/refit
./enable.sh
```
from a terminal shell.

Install Linux

Download and burn Slamd64 from http://www.slamd64.com. The regular 32-bit Slackware will work too of course, and it is a better choice if you need to optimize space rather than speed. In a TV computer, speed is more important than space (1 GB of RAM is plenty), so for me the 64-bit choice was obvious.
- Insert the DVD and reboot. Click on the penguin when rEFIt's boot menu is displayed. Or use the arrow keys on the keyboard and press return. When the bootloader appears, boot the default kernel.
- Do fdisk /dev/sda to change the partition type of the Windows partition created in the previous step. This partition is identified by not having "Id" ee or "Id" af. For example, a FAT32 Windows partition will have "Id" b and "System" W95 FAT32. Most probably it will be the third partition, /dev/sda3. This assumption is made from here on.
- Change the partition type to 83 (Linux), write the partition table to disk and exit.
- Do not create a swap partition, since it will use up the last partition that is compatible with both MBR and EFI-style partitioning. If you want swap space you can always create a swap file later instead.
Do setup and install the stuff you want. The Slamd64/Slackware default selection is recommended. Installation of the default selection from DVD takes about 14 minutes.
- You can try creating a bootable USB stick if you like, I didn't bother.
- Don't install LILO at this point, do it manually later.
- Configure "no modem" and "USB connected mouse".
- Configure the network: you will need an ethernet cable to use it. You can switch to a wireless connection later, but the stock kernel in Slackware 12.1 doesn't recognize the wireless hardware in the Mac mini.
- Enabling sshd is a good idea, so you can work on the Mac mini system from your regular computer.
- Choose UTC for the hardware clock.
- Avoid reiserfs. Hans Reiser will be spending many years in jail for murdering his wife, and this will undoubtedly impact future support and maintenance. Ext3 is good enough for the system disk, and my current personal favourite is XFS for large external data disks.
- Do not reboot after leaving setup! You must install LILO first. If you rebooted by mistake, insert the DVD again and choose Restart from the rEFIt menu, and then boot from the DVD. When you get the root shell prompt, mount your Linux partition via:
```
mount /dev/sda3 /mnt
```
  and continue with the next step below.
Install LILO manually from the shell command line. Use nano or pico to create /mnt/etc/lilo.conf:
```
lba32
boot = /dev/sda3
prompt
timeout = 100
vga = normal

image = /boot/vmlinuz
  label = Linux
  root = /dev/sda3
  read-only
```
Install LILO with lilo -C /mnt/etc/lilo.conf.
Reboot. The rEFIt menu should now present a penguin for the hard-disk Linux installation. Use this selection to start LILO. After a few seconds, the LILO screen appears, and the default kernel will boot. When the login prompt appears, you will be able to login either on the console, or via ssh -l root ... I prefer to use ssh from my regular workstation, but your mileage may vary. If you do use ssh, remember to disable remote root login as soon as you have created a non-root account.
When you have verified that booting into Linux from the hard-disk works, you can make it the default boot option. To do this, boot into MacOS one more time. Start the Terminal or login via ssh, and enable legacyfirst in the file /efi/refit/refit.conf on the MacOS file system. This will make Linux the default choice when rebooting. Decrement the rEFIt and LILO timeouts if you want Linux to boot faster.
Slackware 12.1 has an unnecessary delay during boot due to some stupid Gnome program called /usr/bin/gtk-update-icon-cache which takes forever to run. This is called from /etc/rc.d/rc.M. The boot sequence can be sped up a lot simply by editing rc.M so that these calls are done in the background instead. I wouldn't be surprised if the calls could be eliminated completely with no ill effects, but running them in the background should be pretty failsafe.

Install drivers for wireless networking

This is an optional step: if you want to use the IEEE 802.11g (wireless) interface you will have to download and install a snapshot of Madwifi via Subversion:
```
svn co http://svn.madwifi.org/madwifi/trunk madwifi-todays-date
cd madwifi-todays-date
make
sudo make install
sudo modprobe ath_pci
```
Configure WPA encryption and the init scripts:
- Edit /etc/wpa_supplicant.conf and enter your SSID and passphrase (the "psk" entry).
- Edit /etc/rc.d/rc.wireless.conf and create an entry for the MAC address of your ath0 interface, together with a matching ESSID for the access point. Example:
```
12:34:56:78:9a:bc)
    INFO="Mac mini builtin Atheros AR5424 adapter"
    ESSID='Name of my wireless network'
    WPA="wpa_supplicant"
    WPAWAIT=10
    ;;
```
- Edit /etc/rc.d/rc.inet1.conf for the IP-specific stuff. Example entry for a static address:
```
# Config information for wireless ath0:
IFNAME[4]="ath0"
IPADDR[4]="192.168.0.7"
NETMASK[4]="255.255.255.0"
USE_DHCP[4]=""
DHCP_HOSTNAME[4]=""
```
  Note: if your wired and wireless IP addresses are on the same subnet, the gateway will be routed via the wired interface (eth0) unless you disable it and re-create the default route with the route add -net ... command.
- The driver for the Atheros device apparently drops the connection intermittently while it performs background scans for new networks. This harms performance, and it is completely unnecessary unless you use your Mac mini as a mobile computer. To disable this background scanning, put the following in /etc/rc.d/rc.local:
```
if [ -x /sbin/iwpriv ]; then
  /sbin/iwpriv ath0 bgscan 0 || true
fi
```

Install a new kernel

This is an optional step, and it can be done later if you prefer. I like to compile the latest stable kernel on a new machine, just to make sure that I have fresh drivers in case I need to troubleshoot anything. This is how I do it:

After downloading and unpacking the kernel source:
```
cp /boot/config .config
yes "" | make oldconfig
make
make modules_install
cp arch/x86_64/boot/bzImage /boot/vmlinuz-2.6.xy.z
```
Compiling a 2.6.26.2 kernel takes about half an hour on a 1.83 GHz machine. After this is done, make a new entry in /etc/lilo.conf, run lilo, and reboot.
If the new kernel works, make it the default kernel and repeat the earlier step where you compiled the wireless driver (if you did this before). Do a make clean first if you re-use the same madwifi source directory.

Detach the console

This is an optional step. If you intend to use the machine as a "headless" server, or as a keyboard- and mouseless TV computer, then this is the point where you can safely detach the keyboard, mouse, and monitor, and just trust the network from here on.

Configure X11

This is an optional step. Nothing special is needed in order to connect with a VGA or DVI monitor, but specifying Driver "intel" in Section "Device" in /etc/X11/xorg.conf will enable a driver that knows about this particular hardware.

There are some "quirks" involved when configuring X11 for TV output via Apple's DVI-to-video adapter. This is not unexpected since all types of TV output for some reason seems to be associated with idiosyncracies, regardless of the actual hardware.

TV output on the Mac mini is covered in detail on my web page TV Output on a Linux Mac mini.

Configure sound

Sound works out-of-the-box with the latest Linux kernels. But it's always a good idea to initialize the ALSA settings properly. Do the following commands:

alsamixer
alsactl store

You use alsamixer to unmute the Master and Front controls, as well as any other ones that you want. Unmute by pressing the "M" key on your keyboard. Press it again and it becomes muted. You probably want it unmuted. Press the "Escape" key to terminate, and do alsactl store to store your settings.

For some reason, the full volume range does not seem to be available to ALSA unless you first boot into MacOS and turn up the volume all the way in the Sound settings in System Preferences. Make sure you do this for the Headphones output if that's what you are going to use when running Linux.

Also make sure that your non-root local users are members of the group audio so they get write permission to /dev/dsp and the other audio devices. Membership in the groups video and cdrom is also recommended.

Final adjustments

Optional...

Configure ntpd, just like you would configure it on any other machine.
Connect an external disk. The first external disk you connect will get the name /dev/sdb2. So you can just put that in your /etc/fstab. There are firewire disks that have the same form factor as the Mac mini. I bought a cheap 750 GB model from Iomega and created an XFS file system on it. This setup has worked very well so far.
Make UTF-8 the default encoding. Change the definition of $LANG in the file /etc/profile.d/lang.sh into:
```
LANG=en_US.UTF-8
```
This will greatly facilitate interoperability with the ISO-10646 compliant world.
Enable lm-sensors so you can monitor the CPU temperature. You need to do modprobe coretemp first, then you can just write sensors to see the individual temperatures of the two cores.

Energy profile

One good reason for using a Mac mini is that it uses very little electricity. I made a couple of simple measurements, while running Slackware.

Idling: 26 W.
Unpacking a kernel tarball: 35-40 W.
Compiling the kernel: 35-40 W.
Reading data via 100 Mbit/s ethernet: 30 W.
Suspend to RAM: 9 W.
Note: I still haven't figured out how to wake the Mac mini from sleep without touching the power button, so the suspend-to-ram function is not yet very useful to me...

Energy profile for my Iomega MiniMax external drive, containing a Seagate ST3750840AS 750 GB disk:

Idling, reading, writing, seeking: 17 W.
Spinned down: 9 W.
Note: spinning down the disk with sdparm -C stop /dev/sdb only works when it is mounted via USB, but not with Firewire.