Thursday, February 12, 2015

How illumos sets the keyboard type

It was recently pointed out that, while the Tribblix live image prompts you for the keyboard type, the installer doesn't carry that choice through to the installed system.

Which is right. I hadn't written any code to do that, and hadn't even thought of it. (And as I personally use a US unix keyboard then the default is just fine for me, so hadn't noticed the omission.)

So I set out to discover how to fix this. And it's a twisty little maze.

The prompt when the live image boots comes from the kbd command, called as 'kbd -s'. It does the prompt and sets the keyboard type - there's nothing external involved.

So to save that, we have to query the system. To do this, run kbd with the -t and -l arguments

# kbd -t
USB keyboard

# kbd -l
layout=33 (0x21)

OK, in the -l output type=6 means a USB keyboard, so that matches up. These are defined in <kbd.h>

#define KB_KLUNK        0x00            /* Micro Switch 103SD32-2 */
#define KB_VT100        0x01            /* Keytronics VT100 compatible */
#define KB_SUN2         0x02            /* Sun-2 custom keyboard */
#define KB_VT220        0x81            /* Emulation VT220 */
#define KB_VT220I       0x82            /* International VT220 Emulation */
#define KB_SUN3         3               /* Type 3 Sun keyboard */
#define KB_SUN4         4               /* Type 4 Sun keyboard */
#define KB_USB          6               /* USB keyboard */
#define KB_PC           101             /* Type 101 AT keyboard */
#define KB_ASCII        0x0F            /* Ascii terminal masquerading as kbd */

That handles the type, and basically everything today is a type 6.

Next, how is the keyboard layout matched. That's the 33 in the output. The layouts are listed in the file

Which are a key-value map of name to number. So what we have is:


And if you check the source for the kbd command, 33 is the default.

Note that the numbers that kbd -s generates to prompt the user with have absolutely nothing to do with the actual type - the prompt just makes up an incrementing sequence of numbers.

So, how is this then loaded into a new system? Well, that's the keymap service, which has a method script that then calls


(yes, it's a twisty maze). That script gets the layout by calling eeprom like so:

/usr/sbin/eeprom keyboard-layout

Now, usually you'll see:


which is fair enough, I haven't set it.

On x86, eeprom is emulated, using the file


So, to copy the keyboard layout from the live instance to the newly
installed system, I need to:

1. Get the layout from kbd -l

2. Parse /usr/share/lib/keytables/type_6/kbd_layouts to get the name that corresponds to that number.

3. Poke that back into eeprom by inserting an entry into bootenv.rc

Oof. This is arcane.

Sunday, February 08, 2015

Tribblix scorecard

I was just tidying up some of the documentation and scripts I used to create Tribblix, including pushing many of the components up to repositories on github.  One of the files I found was a quick sketch of my initial aims for the distro. I'm going to list those below, with a commentary as to how well I've done.
It must be possible to install a zone without requiring external resources
Success. On Tribblix, you don't need a repo to install a whole or sparse root zone. You can also install a partial-root zone that has a subset of the global zone's packages. (Clearly, adding software to a zone that isn't installed in the global zone will require an external source of packages, although it's possible to pre-cache them in the global zone.)
It must be possible to minimize a system, removing all extraneous software including perl, python, java.
Almost successful. There's no need in Tribblix for any of perl, python, or java. There are still pieces of illumos that can drag in perl in particular, but there is work to eliminate those as well. (One corollorary to this aim is that you can freely and arbitrarily replace any of perl, python, or java by completely different versions without constraint.)
It should be possible to upgrade a system from the live CD
In theory, this could be made to work trivially. The live CD contains both a minimalist installed image and additional packages. During installation, the minimalist image is simply copied to the destination, and additional packages added separately. As a space optimization, I don't put the packages in the minimalist image on the iso, as they would never be used during normal installation.
It should be possible to use any filesystem of the user's choice (although zfs is preferred)
Success. Although the default file system at install is zfs, the live CD comes with a ufs install script (which does work, although it doesn't get uch testing) which should be extensible to other file systems. In addition, I've built systems running with an nfs root file system.
It must be possible to select which versions of utilities are to be installed; and to have multiple versions installed simultaneously. It should be possible to define one of those installed versions as the default.
Partially successful. The way this is implemented is that certain utilities are installed under /usr/versions, and it's possible to have different versions co-exist. I've tried various levels of granularity, so it's a work in progress. For example, OpenJDK has a different package for each update (so you can have 7u71 and 7u75 installed together), whereas for python I just have 2.7 (for all values of 2.7.x) and 3.4. There are symlinks in the regular locations so they're in the regular search path, which can be modified to refer to a different version if the administrator so desires, but there isn't a built-in mechanism such as mediators - by default, the most recently installed version wins.
It must be possible to install by functionality rather than requiring users to understand packages. (Probably implemented as package groups or clusters.)
Success. I define overlays of useful functionality to hide packages, and the zap utility, the installer, and the zone tools are largely based around overlays as the fundamental unit of installation.
It should be possible to use small system configurations. Requiring over 1G of memory just to boot isn't acceptable.
Success. Tribblix will install and run in 512M (with limitations - making heavy use of java or firefox will be painful). I have booted the installer in slightly less, and run in 256M (it's pretty easy to try this in an emulator such as VirtualBox), but the way the installer works, by loading a full image archive into memory, will limit truly small configurations, as the root archive itself is almost 200M.
It should be possible to customize what's installed from the live CD (to a limited extent, not arbitrarily)
Success. You can define the installed software profile by choosing which overlays should be installed.

Overall, all of those initial aims have been met, or could easily be met by making trivial adjustments. I think that's a pretty good scorecard overall.

In addition to the general aims for Tribblix, I wrote down a list of milestones against which to measure progress. The milestones were more about implementation details rather than general aims (things like "migrate from gcc3 to gcc4", "build illumos from scratch", "become self-hosting", "create an upgrade mechanism", and "make a sparc version", or "have LibreOffice working"). That's where the "milestone" nomenclature in the Tribblix releases comes from, although I never specified in which order I would attack the milestones, it just makes for a convenient "yes, I got that working" point at which I might put out a new iso for download.

In terms of progress against those milestones, about the only one left to do that's structural is the upgrade capability. It's almost there, but needs more polish. Much of the rest is adding applications. So it's at this point that I can really start to think about producing something that I can call 1.0.