Installing Gentoo/Linux on the TiBook 1Ghz

Updates

Contents

• Why?
• Basic configuration
• Xfree
• Mac OS and mol
• Gentoo-specific stuff
• Useful links

Why ?

• Good performance. Although it isn't as fast as the most recent x86 computers, even laptops, it still packs enough punch to make most tasks feel pretty comfortable.
• Good linux support. Even though there remains a few dark spots, most things do work without a hitch. The hardware is pretty standard, and there are no bad surprises to expect. Plus, the linux-on-powerpc community is relatively small, but paradoxically enough it often makes it easier to get support from others.
• Very good "mobility". The 15" is not precisely small (as compared, e.g. to the 12"), but it isn't too big either, and quite light. Add to that its huge autonomy (I often get 4 hours on battery) and the fact that it doesn't heat too much, and it gives you a great tool to remain productive during long trips.
• Reliable hardware, excellent manufacturing and support. The people at Apple definitely know their job, and do it well. And let's face it : hardware malfunctions are the worst kind of pain in the ass, particularly on a laptop.
  Update : Well, reliable or not, I still had to have the logic board replaced, but apparently I was just very unlucky, and Apple Care dealt with it in less than a week, without even pestering me for using linux on it.
• Mac OS X. A very nice OS, not as morally tainted as windoze, and offering a lot of compatibility with linux thanks to their common unix basis.
• Definitely the coolest looking laptop ever. No kidding. And the wide screen is sooo nice when it comes to watching movies.

• Not top notch performance. The 1Ghz G4 doesn't compare well against > 2Ghz x86 CPUs. But it shouldn't bother most users, and I don't think it's really crucial on a laptop.
• A few applications available on the x86 don't work on ppc. Nothing crucial, but it's still quite disturbing not to have support for arts in xmms, and there is a lack in the field of video editing tools.
• No wine*. No native support for games like ut or quake. But then again it's not a shame to reboot the other OS once in a while.

• OSX is not free (I mean as in freedom of course). Not entirely at least, even though apple has made a lot of progress in that direction. Of course, this will only matter to the Free Software/Open-Source integrist hidden inside every decent person :)
• OSX is heavy. It doesn't work well without a huge amount of ressources, and uses those at any time. Hell, it's much heavier than the worst kde environment (which I like a lot, by the way). On linux you're always free to switch to, say, fluxbox or the console (ain't nothing like good 'ole vi...) and save your computer's power for something else.
• The Quartz GUI can be a repellant for some. I'm among those. It sure is beautiful, but sooo slooooow compared to any decently configured linux GUI.
• Configurability. That's really the bone of contention here. In linux you can go assured that whatever you want in terms of behaviour, look, etc, there is a way the system can be configured that way. In OSX, at least for the UI part, you're limited to what an engineer - certainly very gifted - at Apple thought would be best for you. Many people probably like it that way, but I really don't.
• The support for the GNU/OSS apps brought to OS X by the Fink project is at the moment far from what it is on your average linux distribution. Since I only use those apps, the choice for my main OS was quite clear.

Basic configuration

Filesystem

Partitioning a macintosh is a bit trickier than a x86. You have to keep in mind the facts that the first partition is for the partition table, and that you need a 800k hfs bootstrap partition for yaboot, the ppc bootloader. You may also need more micro-partitions at the start of the disk, for the mac os9 extensions, should you choose to retain "Classic" support in mac OSX. Thus it is a good idea to install OSX first, then linux, and take extra care if you ever have to reinstall mac os (in case you have to do that one day, I'd advise you to do it from linux, by booting off the install cd/dvd in mol - startmol --osx --cdboot).
For the linux filesystem, you should make it ext2/3 rather than reiser, which does not really support ppc at the moment. If you intend to use your powerbook on battery a lot, you might want to stick with ext2, as, combined with the noflush daemon, it will limit your disk accesses.
You may also need a shared partition which both mac os and linux can access read-write (linux only has limited read support for OSX's hfs+, and OSX has no support whatsoever for ext). Although the very old hfs filesystem also works, the best solution still is FAT32, which you can create from linux using the mkdosfs utility from dosfstools, and mount as vfat in linux and with "mount_msdos" on OSX. If you only need limited sharing and intend to use mainly linux, you can also do it with mol and any combination of scp/ftp/nfs.
Update: there is now a new kernel hfs+ module from Ardistech, which supports reading OR writing at a very decent speed (as fast as FAT, if not more) on hfs+ volumes, and also provides support for file permissions and ownership, definitely a plus over FAT. This doesn't work with the benh stable (2.4.20) branch, but it has already made its way into the instable branch (2.4.21pre), which is available only by rsync (from rsync.penguinppc.org::benh-devel)or bk. The lucky gentoo users will only have to emerge the latest ppc-sources (>=2.4.21-r1) to get it. It seems to be quite reliable, I've only heard of one incident when it messed up a partition on a 2Gb write.

Kernel configuration

You will have to use a benh kernel to get all the functionalities of your powerbook to work, or any kernel with the benh patch (2.4.20-benh-9 or newer will do for sleep support). I wouldn't recommend combining it with any other patch you're not sure of , especially the more experimental ones (do not even try to meddle with the 2.4 preemptible stuff!), as those probably won't add anything useful, and are more likely to bork everything.
To get a benh kernel on gentoo, just do "emerge ppc-sources-benh", and you'll find the patched source tree in /usr/src/linux. On other distributions, you should also be able to get it in a similar way (apt-get install kernel-patch-benh on debian), although this will sometimes (e.g. on debian) only download the patch, leaving it up to you to apply it ("patch -p1 < /path/to/patch" in /usr/src/linux). You may also download it from http://kernel.org.
Then you should go through the kernel configuration and compilation like this:

#make menuconfig
#make dep && make clean vmlinux modules modules_install

Things that you need to remember more specifically for the configuration are:

• The "Mac devices drivers" section. Activate PMU and power management with APM emulation, as well as adb support, using the input layer but not the raw keycodes, and the mouse 2/3 buttons emulation. Here is a screenshot of my menuconfig.
• Under "Platform Support", enable altivec support (it's one of the G4 greatest strengths, and quite a few apps are getting support for it) and CPU frequency scaling.
• Under "char devices", select /dev/agpgart with Apple Uninorth support, and Direct Rendering Manager with the Radeon driver. Put those as modules as you may have to update them. Do not activate "Enhanced Real Time Clock Support". Screenshot here.
• You will need framebuffer support (found under "Console drivers") for "Open Firmware devices" and "ATI radeon display".
• In the net options, in case you intend to use mol with networking support (why wouln't you?), you will need a certain amount of packet filtering/ NAT support, see the mol section for details.
• To be able to use the built-in cd-burner, you will need scsi emulation in the ide section. Do not put both this and "ide-cd" in the kernel at the same time, or else put them both as modules.
• The oss module for the powerbook is "dmasound_pmac". Although it works, the alsa sound module does a better job, as explained later on in this document, so my advice would be to keep it as modules, and give alsa a try.
• The ethernet driver is "Sun Gem". The wireless aircard should also work, using the "Hermes" chipset driver with support for Apple aircard , but I haven't had the opportunity to test it yet.

For a quick start or reference, you can take a look at my own .config file, but be aware that there is some stuff in it, like more support for packet filtering, that is not necessary for everyday use. Once you have built it, copy the vmlinux to /boot with the apropriate name, edit /etc/yaboot.conf accordingly, and run ybin -v to update your bootblock (or mkofboot -V if you need to set up a new bootblock, on a fresh install or after (re)installing Mac OS).

USB and firewire support

USB support gives no issues at all. You only need usb-ohci support in your kernel, plus specific drivers for what you want to do with the usb. For example, I use my usb for a cd-burner, a mouse and occasionaly a usb key, and my kernel config looks like this, with scsi generic and cdrom support on top of it.
Firewire works all right too, as far as I can tell, but its usage can be a bit trickier. I use firewire for an external hd, so I have enabled "IEEE 1394", "OHCI 1394" and "SBP-2" support in my kernel, along with "sd_mod" (scsi disk support, the hd actually appears as a scsi device, as usual). But you have to remember that firewire is definitely not hot-pluggable on linux, and doesn't get along too well with some other stuff, such as PMU sleep. Thus you will want to leave these functionalities as modules. Here is an init script I wrote to mount/unmount the firewire filesystem on mine. Don't know why I have to modprobe sbp2 twice in a row, though, since the scsi device never registers after the first modprobe.

Sound issues, Alsa

I have encountered a few issues with the oss sound driver for the powerbook, dmasound_pmac. The sound would get all borky for no obvious reason from time to time, leaving me with no solutions but to manually unload and reload the module. The playing would regularly skip as soon as I tried something a little CPU-intensive. And mplayer had a hard time using oss output properly, which resulted in a sound output that skipped every few seconds. That last problem could be solved independantly by using "ao sdl" instead of "ao oss", but anyway I've found the alsa sound driver (that is the "powermac" driver for the powerbook) to be much more reliable.
Although I've got oustanding issues with just alsa per se, like a crackling noise on mp3 playback, which is not exceptional on ppc, alsa with OSS API emulation works flawlessly for me, and is on the whole much better than the original OSS driver. To get alsa sound drivers on gentoo with OSS emulation, just do:

# ALSA_CARDS="powermac" emerge alsa-driver alsa-utils alsa-oss

then edit the /etc/modules.d/alsa file to have it look like what follows, then run modules-update.

alias char-major-116 snd
# OSS/Free portion
alias char-major-14 soundcore
## ALSA portion
alias snd-card-0 snd-powermac
## OSS/Free portion
alias sound-slot-0 snd-card-0

# OSS/Free portion - card #1
alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss

alias /dev/mixer snd-mixer-oss
alias /dev/dsp snd-pcm-oss
alias /dev/midi snd-seq-oss

options snd cards_limit=1

Alsa sound can then be started with the init script /etc/init.d/alsasound, provided the oss sound modules aren't already loaded. You may have to adjust the output and maybe unmute the speakers with alsamixer/aumix. To get alsasound at boot, just remove the oss modules from /etc/modules.autoload if necessary, and run "rc-update add alsasound boot".
As a side note, I've had mixed experiences with alsa support of pmu sleep, wich sometimes throws me a kernel "Oops" on snooze. So I usually switch back to dmasound_pmac before putting it to sleep.

Miscellaneous

• The built-in modem is actually a usb device, which doesn't appear in /proc/pci unless configured. To get it to work, the lucky gentoo users will only have to emerge hcfusbmodem, then run /usr/sbin/hcfusbconfig. For the others, you may get the driver from this website.
• CPU frequency scaling enables you to change on the fly the range of frequencies your CPU is allowed to run at, and the profile it uses to choose a frequency within this range, which is quite useful to save power on battery. At boot, it defaults to a maximum of 66%, that is 666Mhz. To change that to, say 75% to 100%, do:
  echo '0%75%100%performance' > /proc/cpufreq
  To go back to 66% with more care for powersaving, do:
  echo '0%66%66%powersave' > /proc/cpufreq
See /usr/src/linux/Documentation/cpufreq for more info on this one. And if you need to use it often, consider putting it in an init.d script.
• If you don't want to experience time drifts between linux and OSX, set your harware clock to local time in linux. On gentoo this is done by putting CLOCK="local" in /etc/rc.conf and linking /etc/localtime to the appropriate timezone from /usr/share/zoneinfo/ .
• There is a small utility called pbbuttonsd that allows you to use the function keys to change the display's luminosity or the sound output, just like in Mac OS, and can be configured to deal with powersaving issues instead of pmud. emerge pbbuttonsd and powerprefs on a gentoo, you won't regret it.

Xfree

Mac OS and mol

• To get full networking from the hosted OS, you will need, as I've already mentionned, a limited support for packet filtering and ip forwarding in your kernel. More precisely, you must select:
  Socket Filtering (CONFIG_FILTER)
  Packet Socket (CONFIG_PACKET)
  Network packet filtering (CONFIG_NETFILTER)
  Connection tracking (CONFIG_IP_NF_CONNTRACK)
  IP tables support (CONFIG_IP_NF_IPTABLES)
  Packet filtering (CONFIG_IP_NF_FILTER)
  Full NAT (CONFIG_IP_NF_NAT)
  MASQUERADE target support (CONFIG_IP_NF_TARGET_MASQUERADE)
• Once you're happy with your kernel, simply emerge mol, and let portage take care of everything (nearly). It will if necessary emerge iptables and dhcpd as well.
• Finish the configuration by editing the molrc.* files in /etc/mol, particularly - in the case of OSX - molrc.osx (that's where you specify the maximum amount of ram that you will give to mac os, and the hfs partititions it will have access to, including OSX's root) and molrc.net, where you should enable the "tun" network interface (that is done by putting "netdev: tun0 -tun" in molrc.net). Then run molvconfig and select a set of working video resolutions, and check the resulting config in molrc.video. It is advisable to keep your default resolution quite low, like 800x600x16, to make mol snappier. Configure your keyboard by running "startmol --keyconfig".
• The tun networking interface creates a local network between the linux host and the hosted os, which is managed through a dhcp server. All of this is configured in the tunconfig (/etc/mol/tunconfig on gentoo) script, and as far as I can remember, the default script provided by the gentoo install works out of the box. Here is what it looks like on mine.
• Boot OSX with "startmol --osx" in a console or an xterm. The first time you do so, you will need to install sound and networking drivers on the mac os side, they can be found in the "MOL-Install" folder on your desktop. A new network interface should appear in your system preferences, just tell it to use dhcp, and have fun...
• ...but don't forget to reemerge mol if you build a new kernel.

Gentoo-specific stuff

• The proper set of CFLAGS to use with the G4 is
  -O2 -pipe -mcpu=7400 -maltivec -mabi=altivec -mpowerpc-gfxopt -fsigned-char
  If like me you come from the x86 world, remember that there is no -march flag on ppc. The mcpu can be changed to 7450, which doesn't change anything as far as I know, but there is no mcpu=7455 flag, although this is the official denomination of this model of G4. I wouldn't advise you to try -O3 instead of -O2, as it takes longer to build, and on a G4 only generates binaries that are more unstable and actually slower most of the time.
• The USE flags work just like on the x86, with the available flags listed in ${PORTDIR}/profiles/use.desc. Just remember that the "avi" flag must not be set, since it only adds support for a few Windows binary codecs. Same goes for the "x86" flag, of course. If you intend to use the kde environment, I would recommend setting the "pic" USE flag, which will build binaries that are ready to be prelinked, which in turn will make all "libraries-heavy" applications, such as those from kde, start in about half as much time. To prelink your gentoo, simply emerge prelink, edit /etc/prelink.conf to suit your needs, then run "prelink -amfR".
• Ebuilds marked as "~ppc" are generally less dangerous than those with the "~x86" keyword on the x86, but some of them still aren't for the faint of heart, so be sure you're up to it before setting it as an "ACCEPT_KEYWORD" in your make.conf. Most users would probably be better off using it only when they know they need it. On the other hand, some ebuilds have no ppc keywords at all, but this doesn't necessarily mean that they won't work on ppc, only that they haven't been tested on it yet (ebuilds that clearly do not work would be marked as "-ppc"). So feel free to try emerging them anyway (do this with end-user apps of course, not with base system components, unless you actually like repairing or reinstalling messed up gentoos), either by adding a ppc keyword to the ebuild, or by simply running "emerge /path/to/foobar.ebuild", and if succesful don't hesitate to send an e-mail to the gentoo-ppc-dev mailing list to report your deed along with the output of "emerge info" on your system.
• You can take a look at my own make.conf. Notice that I do all portage stuff on an external firewire hd to take advantage of the added speed and give the internal hd a break, which accounts for all the directory settings.

Useful links

• The source of all worthy knowledge. http://www.gentoo.org
• The ultimate Gentoo Problems Solver, aka the gentoo forums. The ppc section at the bottom is particularly interesting for you, but don't disregard the others. For a quick answer or a little geeky chit-chat, you may also give irc a go, on #gentoo-ppc at freenode.net.
• A must-read for those who would choose to go debian, with lots of relevant info for the others as well.
• Another must-read, dealing with debian, gentoo and yellow dog.
• Another personnal page, with good tips on how to configure an external monitor.