Feb 262009

Yes I know everyone and their dog has already written a review of the Intel iMac, but I have not done so yet. This is a review of the 24″ iMac (and I’m already hating that incorrect capitalisation) with the specific intent of putting Ubuntu on. This is not some kind of weird anti-OSX statement; I already have a laptop with OSX installed on it and it does seem like a fun operating system.

But this is a replacement for my main desktop, and I really want a “proper” Unix on it, and Linux will do in the meantime.

First Thoughts

First of all, the screen stand should allow adjustment in the vertical direction; already I can see myself getting out an extremely old and manky tape drive to sit underneath to raise the screen to an appropriate height. Apple ? Your lack of foresight in not including height adjustment is ruining the look of the system!

Nice keyboard! If you do not type much. I am aware that some people really like the skinny Apple keyboards, but it is not for me even though they got off to a good start by not including Windows keys. Back to the Das Keyboard for me I think. The mouse is similar – there’s this nice funky ball on top which is an improvement over the usual scroll wheel (although I am not too sure how well it would work at speed), but just not enough buttons.  Or at least it does not feel like enough buttons. The “one button” with two effects method as appears to be the case here is a little odd and off-putting.

Perhaps Apple needs a special country kit – “Special Clicky Keyboard And Mouse With Too Many Buttons For The Unix Geeks”. How many people end up using a non-Apple keyboard and mouse ? Perhaps not many, but why not cater to them with alternative keyboards and mice ? My Apple keyboard and mouse will be mostly unused.

Where are the memory card slots though ?  It would make things a bit more complete (and the iMac is about one box doing everything) if there were a sensible selection of memory card slots.

In terms of software (and not OSX itself), one thing becomes immediately apparent when booting (and on previous occasions when trying to boot from CD, diagnosing booting problems, etc.). The Apple firmware breaks the first rule of user interface design! Not something you expect Apple to do.

The firmware needs to be just a little bit more expressive about what is going on. You may well be thinking that as a hardcore Unix geek I want to see inscrutable messages from the firmware about initialising that chipset, addresses of where adapter cards are, cpu values, etc. And of course you are right.

But basic messages about starting the hardware would still be helpful.

More importantly however, the Apple firmware should be letting you know what keystrokes are needed to do “unusual” things like boot from a CD, an external hard disk, start the hardware diagnostics, etc. One of the most irritating things about Apple hardware is the need to provide secret incantations to boot from CD  – you hold the “C” key down for “a while” (how long anyway?).

The Install

At this point the “unusual” choices of Apple bite you when it comes to installing a version of Linux intended for use on mainstream PCs. First you have to install rEFIt, then you install Linux off CD (and mess around with the MBR partition table), then have to remember to “resync” the partition tables.

Seems there’s an EFI partition table and an MBR partition table that need keeping in sync. Having two partition tables immediately strikes me as a dumb idea. When Windows is involved, there is probably no fix for this problem, but why is Linux still not doing things properly ? Or at least not doing the sensible thing by default.

It also means there is effectively a two step boot process – first rEFIt starts, then then starts grub which finally starts Linux; this is not a quick system to boot.

Fixing The Niggles

In any install, there are always little niggles that need fixing. The most obvious is a way to control the brightness of the screen which by default is far too bright. There may well be better solutions out there, but a bit of C coming from http://www.felipe-alfaro.org/blog/2006/09/11/basic-backlight-support-for-macbook-pro

A quick compile and install in /opt/bin/bl and root can set the backlight brightness with :-

bl (1-15)

Adding this in an appropriate way to /etc/rc.local ensures that the backlight is set on every boot.

It also appears that we need to do a bit of hacking to support the sound properly. Adding an option to /etc/modprobe.d/options specifies the “model” of soundcard we are using to get sound working :-

options snd-hda-intel model=imac24

A quick reboot and sound is working (microphone not tested!).

For some reason the module that is used to gain access to the iMac temperature probes is not loaded automatically. Adding applesmc to the end of /etc/modules gets this loaded (after a reboot or manually with modprobe applesmc). Unfortunately there does not appear to be an immediately obvious way of using this except from the command line.

The wireless network controller apparently works after the addition of the proprietary driver that shows up after doing an update. Admittedly I cannot say for sure because I use a wired setup.

Lastly the IR receiver. I will admit this has currently defeated me although that is partially because I am not that interested. I will of course update this if I get it to work.

Later: Screen Calibration

I later took a look at setting up the screen properly. Proper controls for the screen would have been nice, but configuring from the system turns out to be relatively easy.

First of all I used the OSX screen calibration tool in “expert” mode to generate in ICC file containing the screen profile. Doing this may well be possible inside Ubuntu; I just happened to know where the tool was in OSX.

I then installed xcalib :-

apt-get install xcalib

This could be used to set the monitor profile from the earlier generated ICC file.


It works. After a week or so using it, I am no longer thinking of the iMac as a system being installed and tested but as my standard desktop.

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