A collection of computer systems and programming tips that you may find useful.
Brought to you by Craic Computing LLC, a bioinformatics consulting company.

Wednesday, June 20, 2007

Apache 2.2 - Where are the modules ?

The Apache httpd server has played a critical role in most of my work over the past decade but these days I'm finding more and more reasons to look at alternatives. Its configuration syntax is not pretty, the distribution is bloated, and its performance with some applications (especially Rails) is almost unworkable. Here's another reason to grumble...

I recently compiled Apache 2.2.4 from source. I've done that several times in the past and just did the typical steps of:
# ./configure --prefix=/usr/local/apache2
# make
# make install

That works great and I can fire up the server just fine - until I want to serve an application that involves URL rewriting. I get this error:

[Wed Jun 20 17:00:07 2007] [alert] [client] /Users/jones/instiki/public/.htaccess: Invalid command 'RewriteEngine', perhaps misspelled or defined by a module not included in the server configuration

That tells me that the mod_rewrite module is not being loaded in the httpd.conf file. So I go into that file and search for the LoadModule section. In the past there would be a bunch of LoadModule statements, many of which were commented out. But in 2.2.4 there is only one. This is actually a good thing as it makes the httpd.conf file smaller and easier to look through.

I figured I just needed to add a line that loaded mod_rewrite. I checked my apache2/modules directory to get the correct file name - but there are no modules in there. I checked to see if it was compiled into the executable using this:

# /usr/local/apache2/bin/httpd -l

No, it's not in the list. So where are all the modules? Am I supposed to download them separately from apache.org? Looking on that site doesn't tell me what to do. What's the deal?

Turns out that you have to specify the modules you want at compile time. This is a really, really bad move on Apache's part. I'm sure it is done with the best of intentions but what a pain. In order to get my module I have to go and recompile the whole damn thing... great...

*WAIT* If you have already modified your current apache config files, htdocs directory, etc. copy them somewhere safe before you recompile and install over them!

Here's what I need to do to get mod_rewrite and mod_env compiled so that I can load them dynamically.

# ./configure --prefix=/usr/local/apache2 --enable-rewrite=shared --enable-env=shared

To see the full list of options (215 lines of them) do this:

# ./configure --help

You can get 'all' or 'most' (whatever that means) of the modules using these variants

# ./configure --prefix=/usr/local/apache2 --enable-mods-shared=all
# ./configure --prefix=/usr/local/apache2 --enable-mods-shared=most

I chose the latter when I recompiled and that gave the two that I need plus hopefully any others that I might need in the future. So my specific steps were:

# ./configure --prefix=/usr/local/apache2 --enable-mods-shared=most
# make
# make install

Then I went into the httpd.conf file, put back a couple of changes that I had made previously and went looking for the LoadModule lines. Well, I guess I got what I asked for... I asked it to compile most of the modules. It did that and it has set up the config to load all 43 of them!

All I want are two modules, for Pete's sake... so I reckon I want to delete the others, right? WRONG! Without the new configure directive, a bunch of the standard modules are compiled in the server. With the new directive, they are loaded dynamically. So if you delete these LoadModule lines then a load of other stuff will break.

With all this done, I can now get back to where I started with a functioning Apache installation. I hope this note helps you avoid the couple of hours of frustration that I just enjoyed.

Apache is a great piece of work, don't get me wrong, - but nonsense like this is really annoying.

If you are in the market for an alternative you might want to consider Nginx (http://nginx.net/), a relatively unknown http server that is getting a lot of good press in the Rails community.


Blogger said...

If you need your ex-girlfriend or ex-boyfriend to come crawling back to you on their knees (no matter why you broke up) you need to watch this video
right away...

(VIDEO) Want your ex CRAWLING back to you...?

Blogger said...


Get professional trading signals sent to your cell phone daily.

Start following our signals today & profit up to 270% daily.

Archive of Tips