etbe - Russell Coker

old drivers

This morning when walking through a shopping center car park on my way to work a grannie came fairly close to squashing me. She accellerated her Mazda 323 backwards as hard as possible and hit a purple Magna. The back ends of both cars were seriously damaged, and the Mazda (which received the worst damage) was possibly a write-off (it doesn’t take that much damage to make an old car an insurance write-off). The damage was surprising given that there was only about 4 meters between the cars before the crash, the roar of the engine however did indicate that full accelleration was being used. The area between the vehicles was where I had just walked a few seconds earlier…

I phoned the police and waited until they arrived. They might end up forcing her to have a driving test, but it’s most unlikely that she will lose her license. One of my relatives passed such a test more than 10 years after I refused to ever be a passenger in his car.

What is needed is periodic testing of all drivers with the same standards as used for initially getting a drivers license (currently the standards are much lower). I would probably have to practice my parallel parking before such a test (it’s something I hardly ever do) but I expect that I wouldn’t have any difficulty in passing – as would all good drivers.

creating a new SE Linux policy module

Creating a simple SE Linux policy module is not difficult.

audit(1173571340.836:12855): avc: denied { execute } for pid=5678 comm=”spf-policy.pl” name=”hostname” dev=hda ino=1234 scontext=root:system_r:postfix_master_t:s0 tcontext=system_u:object_r:hostname_exec_t:s0 tclass=file

For example I had a server with the above messages in the kernel message log from the spf-policy program (run from Postfix) trying to run the “hostnme” program. So I ran the following command to generate a .te file (SE Linux policy source):

dmesg|grep spf.policy|audit2allow -m local > local.te

The -m option to audit2allow instructs it to create a policy module. The local.te file is below:

module local 1.0;

require {
      class file execute;
      type hostname_exec_t;
      type postfix_master_t;
      role system_r;
};

allow postfix_master_t hostname_exec_t:file execute;

Then I used the following commands to create a policy module and package it:

checkmodule -M -m -o local.mod local.te
semodule_package -o local.pp -m local.mod

The result was the object file local.pp and in intermediate file local.mod (which incidentally can be removed once the build is finished).

After creating the module I used the following command to link it with the running policy and load it into the kernel:

semodule -i ./local.pp

nerve action – sound vs electricity

Leon Brooks linked to this article claiming that sound not electricity travels through nerves.

When you put a moderate voltage through your body it will cause muscle action (try putting 1000V at low current between fingers of the same hand for safety). The original experiment that suggested that electricity is used involved applying a shock to the legs of a dead frog (see the Wikipedia entry for Luigi Galvani).

For this claim about sound to be valid the electric shocks would have to cause sound in the nervous system. Also sound impulses would have to trigger nerve action (IE the “brown note”). AFAIK neither of these have been proven.

another visual migraine

Late this afternoon I had a visual migraine while driving. I was driving west and the glare from the sun was making it difficult to see so I didn’t realise that I was having a migraine until I stopped. When I finished my journey and went inside a reasonably dark room I started seeing flashes of light (which weren’t apparently bright enough to be noticed when outside). After about an hour the visual effects went away but I still felt weird for the rest of the day.

SFF disks

I recently bought a refurbished HP DL385 server at auction. It turns out that it takes SFF (Small Form Factor) disks and has the ability to take 8 hot-swap disks (not bad for a 2U server).

The machine supports SAS disks and S-ATA disks as well. So the next thing to do is to buy a bunch of S-ATA disks for it.

When I got the machine it reported that the battery for the write-back cache on the RAID controller could not be recharged and needed to be replaced. Apparently this is a firmware bug and I can fix it by upgrading the firmware on the machine. Of course I need to buy some disks so I can do an OS install first.

As an aside it’s amazing how cheap some of the Opteron servers are at auction nowadays.

features of BMW 5 and 7 series

I was reading the brochure about the BMW 530i Touring (which seems to be the BMW name for what is known as a “Station Wagon” in Australia or an “Estate” in Europe). I looked at the brochure on the “Touring” because I am interested in a Station-Wagon – the Sedan version of the 5 series is almost the same in every way other than size and shape.

Here are some of the interesting features:
Adaptive headlights, they turn in to a corner when the car is cornering (showing where you are about to go instead of showing you the scenery off the road) and the high-beam switches off when an oncoming vehicle is detected.

Head-up display for speed, navigation, and other driver-relevant information.

Park distance control (PDC). Gives audio and visual alerts when you are about to hit something at low speed.

Eight air-bags of which only the necessary ones will inflate in a collision, and the inflation power will be determined by the severity of the collision.

Dynamic stability control (DSC), traction control, corner brake control, and more. Described as “all of the known features of DSC”.

Seat-belt pre-tensioners in the rear and pyro-technic tensioners for front seat belts.

Rain sensor that turns on headlights, and optional head-light washers.

According to it’s brochure the 7 series has bumpers that regenerate their original shape in collisions of speeds up to 6Km/h and a tire defect indicator. Apart from that there doesn’t appear to be much benefit over the 5 series apart from more luxury features.

To get the PDF files from BMW Australia (without following my links which BMW will probably break soon) you have to fill in a form with “contact details”. To enter that form you need a browser that works with their javascript (which means not Konqueror) so that you can enter your postcode and be prompted with a list of suburbs that match the post-code. The second-last page of that process allows you to download PDF files and it seems to indicate that your data will not be stored if you don’t continue past the stage where you download the PDF files. It would be good if BMW could get smart and make their PDF files as easy to download as Mercedes does.

In terms of safety features it seems that the 7 series offers little over the 5 series. By comparing the brochures it seems to me that the Mercedes S series (as described in my previous blog post) has many more safety features than any BMW. Assuming that the BMW documents are accurate they don’t seem to compare well with the Mercedes S class. From a quick search on drive.com.au (the best web site for buying used cars in Australia) it seems that the Mercedes keeps it’s value better than the BMW – other people apparently share my opinion of the relative merits of the cars.

In future posts I’ll summarise the features of some other cars that I consider interesting.

reading email on a tram

This morning there were two or three classes from a local primary school on board my tram taking up all the seats (mostly three children to a seat).

So to answer some email and write blog entries I had to sit in a stair-well. Melbourne trams are symmetrical so that they can just change direction at the end of the line (unlike some other trams – the Amsterdam tram line 10 that I used to catch has a circle at each end of the line for the tram to turn). Being symmetrical means that the doors on the left side of the tram are used for passengers to get on and off, and the doors on the right are locked – so the right stairwell is a place you can sit to use a laptop if all the seats are taken.

While I was sitting on the floor some women started talking about me, I heard comments such as “he’s answering his email”, “it must save a lot of time, he could do half an hour of email on the way to work”, and “he must work for an Internet company – look at his shirt” (I was wearing an Intel shirt given out at LCA 2007). At that point I decided to briefly explain the work I do, there’s a limit to the amount of time I can refrain from joining the conversation when people are standing around me and talking about me.

They didn’t seem to understand enough to enable me to explain anything about Linux.

presentations and background color

In response to my last post about using laptops for presentations it has been suggested to me that using white (or a very bright color) as the background color can help some displays synchronise with the signal. I haven’t had an opportunity to test this but it seems likely that as most computers are configured with a white background nowadays the display hardware is optimised for this case.

Another benefit of a light background is that it provides more ambient lighting to the room where the presentation is held. If all the lights are turned off (sometimes there is no dimmer switch) then the radiant light from the screen is the only form of illumination for the room.

Finally with the way the current generation of beamers work there is less heat trapped in the beamer if there is mostly white on the screen. This will hopefully decrease the incidence of hardware failures during lectures (which unfortunately are not uncommon in my observation).

Update:

Based on a comment on this blog entry I did a quick survey of the color scemes, black on white, yellow on blue, and white on green. Black on white got the most votes with some people saying that yellow on blue was most aesthetic while black on white was easiest to read (“clear and boring” was one comment).

One person pointed out that the light diverges slightly so black on white makes the letters look smaller while white on black makes them look bigger. My response to this is to use a slightly larger font.

last beard post

day 107 (last) of the beard
On Tuesday the 23rd of January I shaved off my beard after spending 107 days growing it, see above for the final beard pic. It was an interesting experiment and it’s something that I recommend trying, but I couldn’t keep it.

Having a beard is more effort than being clean-shaven. Eating is more difficult when you are trying to keep your beard out of your food. If you get the full beard (as I did) then the mustache at the sides of your mouth will get into your food (particularly bad for ice-cream). I guess that the benefit of having a waxed mustache would be that the wax would keep it out of the way of the food – the waxed mustache wasn’t just an issue of style!

Madduck suggests that when you drink Guinness you “push your lips past the head and draw up only the dark stuff“. Of course that won’t work if you have a mustache as you don’t want a mustache that’s soaked in beer!

Immediately after cutting off my beard I didn’t shave for almost a week and experienced much less discomfort than I had previously experienced when not shaving for that period. I think that having been used to having a beard an amount of hair that would previously annoy me is not noticeable. Also it seems that the hair was initially softer after I cut off the beard. Maybe shaving somehow makes the hair grow tougher.

When I had the beard I thought that I hadn’t adjusted my body image to match, as every time I looked in the mirror I felt surprised to see it. Once it was gone my new look initially seemed more odd to me than my previous appearance, and it took me a number of weeks to get used to not having a beard.

final goatee picture

final mustache picture

When shaving off my beard I decided to do it in stages, firstly I did a “goatee” cut and then just a mustache. The mustache is a little lop-sided, but I was in a hurry and didn’t plan to keep it for long.

vaccinations

You might expect that a vaccine against a disease that causes cancer would be widely embraced as soon as it was proven safe. If the disease in question was transmitted by contaminated food or water, sneezing, or most of the other ways that diseases spread then it probably would be widely accepted.

However recently there is a recently released vaccine against Cervical Cancer. The virus in question is only transmitted sexually. Apparently 80% of women in the US will catch it before the age of 50 (so it’s obviously not scaring people away from unsafe sex).

There is a strong Christian lobby against the vaccine, their idea is that if sex doesn’t cause debilitating and/or fatal conditions such as cervical cancer then their daughters will have less reason to avoid it. The fact is that religious people are statistically more likely to practice unsafe sex (see this link) so it seems unlikely that preventing one of the STDs that religious people might catch will affect the amount of unsafe sex.

One thing that seems strange about the entire discussion is that no-one has raised the possibility of vaccinating boys. Vaccinating boys could lead to the virus being eradicated. Even if an eradication attempt fails it will help save some of the Christian girls.

etbe – Russell Coker

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old drivers

creating a new SE Linux policy module

nerve action – sound vs electricity

another visual migraine

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features of BMW 5 and 7 series

reading email on a tram

presentations and background color

last beard post

vaccinations

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