Downtown Doug Brown

There are tons of instructions out there for setting up WordPress on a lighttpd server with WP Super Cache. A quick Google search will show you what I’m talking about. I’m not totally happy with them though — it usually boils down to enabling mod_magnet and using a lua script. It’s not too surprising that it requires a bit of trickery because the main instructions that come with WP Super Cache are designed with Apache in mind.

I’d like to share the setup I use on this blog, which takes more manual effort initially but no longer requires the use of a lua script.

I first obtained these instructions from a blog which no longer exists, but the original instructions are still available from the wonderful Internet Archive. Since the original page is no longer around in Google results, I feel like I need to keep the instructions alive. So…here they are, in my own words and modified for a newer version of lighttpd:

First of all, set up WP Super Cache for mod_rewrite mode. It’ll warn you that mod_rewrite isn’t installed and the rewrite rules must be updated — this is perfectly OK because we’re not using Apache.

Now, in the main WordPress directory, create symlinks to everything in the wp-content/cache/supercache/www.domain-name.com directory. Here’s an example symlink command for the “2010” directory:

ln -s wp-content/cache/supercache/www.domain-name.com/2010 2010

I had to create the following symlinks on my server:

2010, 2011, 2012, category, contact, index.html, and microcontroller-lessons

Every time you add a new page with a root directory URL or another year goes by, you will need to add an appropriate symlink or else the supercaching for that page won’t be active–it’ll be served through PHP instead, so the site won’t break if that happens — it’ll just be inefficient.

OK. Now that you have that done, disable directory listings, set the 404 error handler to /index.php, and ensure that index.html comes before index.php in the list of index file names. That last one about index.html being in front of index.php simply ensures your main blog page is served supercached correctly. Anyway, this can all be done in lighttpd.conf:

server.error-handler-404 = "/index.php"
dir-listing.activate = "disable"
index-file.names = ( "index.html", "index.php" )

That’s it! It’s about as simple as it can get.

Is it perfect? No, not at all. It doesn’t matter if you’re logged in or not — if a supercached version of a page exists and you go to its URL, you will get the supercached version rather than a newly-generated version of the page–meaning you don’t get the cool WordPress toolbar at the top. So it isn’t smart enough to look at your cookies or anything like that to only serve supercached files to non-logged-in users. In my case, I don’t really care — I can still access the WordPress Dashboard and that’s all that really matters to me.

It’s also kind of annoying that you have to create a new symlink for everything that is in the “wp-content/cache/supercache/www.domain.com” directory, but I can live with it.

It appears to work because if a supercached version of a page doesn’t exist already, a 404 error occurs, which passes the request onto /index.php, which figures out the original request.

Thanks again to the (now defunct) Zash Blag for the original instructions. There may be better solutions available than this — if there are, please leave a comment! I would definitely be interested in trying them out.

Edit: With the latest kernel updates, this hack should no longer be necessary in Ubuntu 12.04 or 12.10. I’m leaving this post in place for future reference if people run into the same issue with newer iPhone revisions as they come out.

Here’s the scenario: you’re using an Ubuntu distribution (perhaps 11.10 or 12.04 or 12.10, but I’ve only tested this on 12.10) and you’ve followed the various instructions around the internet for tethering your iPhone using a USB connection in Linux, but it just doesn’t work on your iPhone 5 no matter what you try, despite it working on an older iPhone model just fine.

What gives?

The problem is that iPhone 5 support was added to the ipheth driver in the Linux kernel in October, and that particular patch hasn’t been added to the kernel Ubuntu is using yet.

Look at the patch. All they did was add an extra item to the end of a static array. It looks exactly the same as all the rest of the entries, with the exception of a different USB device ID. If you don’t want to backport the patch and recompile the kernel module and all that, we could just modify the binary ipheth driver so one of the existing iPhone device ID entries matches the iPhone 5 instead of its original device ID. It’s a little more tricky to append to the array by just modifying the binary, so changing an existing entry in the array is an easier alternative. Let’s do it!

Make a copy of /lib/modules/<your kernel version>/kernel/drivers/net/usb/ipheth.ko and put it somewhere. We’ll mess with the copy, so leave your existing driver alone just to be safe.

Decide on an iPhone model you don’t need support for. In my case, I just picked the iPhone 3GS. In the code of the ipheth driver, find its corresponding USB device ID. For the iPhone 3GS, it’s 0x1294. Now, using your favorite hex editor (I personally like running HxD in Wine), search for that string, but reverse the bytes (unless you happen to be on a big-endian system like PowerPC). So in my case, I would search for the hex string 0x9412. Once you find it, confirm that it has 0xAC05 directly before it. This just confirms it’s part of the device ID table and not just a random chunk of code or data that happens to be the same. OK, so you’ve found it. Replace the old hex string (0x9412) with the iPhone 5’s USB device ID (it’s 0x12a8, so you will use 0xa812).

Save the file.  Manually unload the old driver if it was already loaded by typing:

sudo rmmod ipheth

Now, load the new one:

sudo insmod /path/to/new/ipheth.ko

Try plugging the iPhone 5 in now. It should be recognized as a network interface!

You’ll have to manually load this kernel module with the insmod command every time you reboot your system, and every time you install a kernel update, you should probably redo the patch on the latest version of the ipheth module, but it works! If you’re feeling extra clever, I think you could actually leave the modified version of the driver in place where the regular driver goes and add a line to modules.usbmap so it will automatically load the new ipheth module when the iPhone is plugged in, but I’m not going to get into that.

So there you have it: a quick and dirty way to make your iPhone 5 USB tethering work until Ubuntu either starts using a newer kernel or backports iPhone 5 support.