Using Apache on Mac OS X to serve files outside ~/Sites

I'm working on a web project that basically contains just static HTML and Javascript. (well OK, there's also one, small PHP script, but it might be going away in the near future). I tend to keep all my source code in ~/src, but to host it, I also need it to appear in ~/Sites. After some small trial-and-error, I ended up putting the everything (git repo and all) into ~/Sites, and then symlinked it to ~/src. It wasn't pretty, but it worked.

So I just did some reorganization that pretty much invalidated that old structure. In particular, I have moved everything that needs to be deployed into ~/src/project/web. However, I want it to be accessible via http://localhost/me/project. I tried physically moving the project back into ~/src, and then making a symlink to the subdirectory, but that didn't work. Apache would still produce 403s for all the relevant files. So I had to roll up my sleeves and dive into Apache configuration.

Before I go further, I'm compelled to pull out the old soapbox. I have painfully little experience with Apache - I have never had to configure or support it in a production environment, and that makes me happy. From this position of ignorance, I have decided that Apache is a dinosaur that should have died a long time ago. For example, instead of configuring the server from the request's point of view (as has been popularized by Rails' routing logic), it is configured from the filesystem's point of view. The default Mac OS configuration has, buried somewhere in the middle of the file, a directive that disallows the serving of all files under /. Because, I guess, they would be served by default if that directive wasn't present? But still, nobody seems to want to spend the time to produce a replacement web server, and so we struggle on. </rant>

The default Apache install on MacOS 10.7 uses a split apache configuration file. The bulk of the configuration is in /etc/apache2/httpd.conf. However, each user also gets their own /etc/apache2/users/me.conf, which are all imported into the main configuration. And while the main configuration file specifies the FollowSymlinks option, I discovered that the same is not true in my personal config file. All I had to do was to add the FollowSymlinks option to that configuration file, restart Apache, and everything started working.

So if you have only basic web serving needs, the default config should suffice. If, however, you want/need to spread the files around your disk, you need to mess with the Apache configuration.

Fixing hard disk clicking / aggressive head parking on Mac OS X

I recently bought a Western Digital Scorpio notebook hard drive to put into my 2007-vintage Macbook Pro. Everything seemed fine at first. However, as I used my laptop, I noticed that it would frequently make a quiet clicking noise. At first, I thought that I had gotten a bad disk. However, after doing a little research, it became clear that this is a common problem. This clicking is a "normal" operational noise - it is the sound of the heads parking.

People say that you should just get used to the noise. However, this blog post makes the argument that every one of these clicks is killing your hard disk. Some people claim that this is related to the sudden motion sensor that's built into most (if not all) Apple portables. However, this is a red herring. The disk still clicks even if it is sitting on a table. It is the hard disk's own built-in power management that is causing the head parking. The disk's SMART statistics record the number of head parking cycles. If you want to see this for yourself, you can use either this menu extra or this command line tool (MacPorts). You are looking for the Load Cycle Count value.

To explain the problem (as I understand it), modern hard disks have some responsibility to manage their power consumption. One manifestation of this is to spin down the platters and to park the read/write heads. The operating system can influence the time before the heads are parked by setting the "APM Level" of the drive to a value between 0x00 and 0xfe. Each drive manufacturer is free to interpret this value as they see fit. Mac OS X seems to set a default APM Level for all disks, and I think this value is 0x80. This is fine with Apple-shipped disks, but not necessarily for third party disks.

But wait! Perhaps you have bought the same kind of drive that Apple ships in their laptops. Are you safe? Not necessarily. Allegedly, Apple flashes their own firmware onto the the hard disks that they install at the factory. That's right, you're not running stock disk firmware. My suspicion is that this firmware changes the drive's interpretation of the default APM level. Recently, there was a firmware update from Apple that fixed this problem on disks that were shipped by Apple. Unfortunately, you can't use this utility to flash the new firmware onto a non-Apple drive.

Right, so the two solutions that I see are either:

1. Write our own firmware
2. Set a different APM Level value

Obviously, option 2 looks much more attractive. Bryce McKinlay wrote a utility called hdapm for doing just that. He even includes a launchd configuration to run hdapm as the system starts. One thing not mentioned in the readme is that you need to get the permissions of the launchd config file correct. The file needs to be owned by root (preferably root:wheel), and must not be group- or world-writeable. I also changed the config file a little; here is my version:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
 <key>Label</key>
 <string>hdapm</string>
 <key>ProgramArguments</key>
 <array>
  <string>/usr/local/bin/hdapm</string>
  <string>disk0</string>
  <string>max</string>
 </array>
 <key>RunAtLoad</key>
 <true/>
</dict>
</plist>

The biggest change is that I removed the "LaunchOnlyOnce" and "ServiceDescription" keys. I didn't see a reason to load it only once, and ServiceDescription seemed undocumented. This solution isn't perfect, however. First of all, hdapm uses a seemingly undocumented back door to adjust the APM setting. Ideally, we would actually spawn a daemon that continuously monitors and adjusts the drive's APM level. I'm not yet convinced that Mac OS X won't override my setting. Still, I have been running with this configuration for a couple of days, and things seem to be working well.

I have an open support issue with Western Digital to see if they have a fix for this issue. If there were some way that we could change the way the disk behaves under OSX, we could forego the additional software, which would be great. I've also heard of a utility called wdidle, which allegedly lets you write new idle settings to the hard drive. However, I was unable to find any official site for this software, so I'm not using it.

Finally, I would like to thank two people. First, Doug Aghassi's post really explained the symptoms that he was experiencing and put me on the right track for solving the problem. Thanks, Doug. Also, Bryce McKinlay was kind enough not only to write the hdapm utility, but also to answer the questions that I emailed to him. Thanks, Bryce.

Arduino librxtxserial.jnilib on MacOS

After re-installing MacOS from scratch, I found that I was having problems launching Arduino. I got the following error:

In order to solve this, I followed the instructions at rancidbacon.com. The solution was to use Finder to configure the application to launch in 32-bit mode. I quickly looked to see if I could modify the Info.plist file to enforce this behavior, but I don't see any way to do that.

Another solution from technobabble is to replace the library inside the Arduino app bundle with a 1.6 compatible version.