Enabling Apache 2 mod_log_forensic on Debian GNU/Linux 7.8 (wheezy)

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Assuming you already have Apache up and running, it’s really easy to enable mod_log_forensic in order to look in detail at the http(s) requests that are being made to your website.

This module provides detailed logs of every http request – and can be very  useful to developers when debugging benign requests which are not processed correctly (and result in errors) – and also for looking in more detail at malicious requests that are intended to compromise the security of your website.

All you need to do is add the following to /etc/apache2/apache2.conf:

ForensicLog ${APACHE_LOG_DIR}/forensic_log.log

Then, as root (or using ‘sudo’ if appropriate for your setup) , run:

a2enmod log_forensic
service apache2 restart

After enabling this module,  detailed information about the http requests placed against your web site are are logged to /var/log/apache2/forensic_log.log

Replacing ^M with line break (carriage return or newline) to make viewing log files easier

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Some syslog log files produced  contain  ^M  instead of a newline (or carriage return) at where a line ending would normally be.

Systems which use this pattern include the good old Cisco VCS – still my favourite SIP/H.323 call control platform – and also log files from exciting new video conferencing disruptor Pexip – easily my favourite MCU and imho far and away the “best of breed” of next generation video bridges- although I don’t pretend to be in any way unbiased here!

Whilst the use of ^M is actually very useful (as it allows you to easily use powerful command line tools like “grep” to find & filter relevant/interesting logs when troubleshooting) it can mean that reading the logs  you’ve found/filtered that way can be a little bit difficult – particularly if the log contained several  lines  e.g. as a any SIP message would.

There are a number of ways of cleaning these logs  up to make the logs easier for poor humans to read:

Porting from sheevaplug/pogoplug/goflex to Raspberry pi: “./myprogram: error while loading shared libraries: unexpected PLT reloc type 0x12”

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I appear to have something of a small ARM server habit – with four of them running at home right now.  

I like the fact that running 4 of these servers consumes less power than even a single low-end Intel server would (although I often find myself wishing I had the extra grunt that an Intel box could bring)

Sheevaplug was my first foray into the world of ARM – and I loved it so much that when I stumbled across some Seagate Freeagent Dockstar servers (which are based on the same board as the sheevaplug) in the bargain bin at Clas Ohlson I bought them – and when one of them blew up a year later, I bought a pogoplug (also, at that time, based on the same hardware).

Being based on more or less the same Marvell hardware brought other benefits: it was possible to copy binaries from one system to another and they’d run happily.  

 

My latest acquisition is a £25 Raspberry Pi  unit.  It’s running the new Debian wheezy raspbian Linux distro.  Alas they switched architecture from armel to armhf between the (original?) Debian squeeze and (“new” in mid 2012) Debian wheezy (raspbian) distributions for the Raspberry Pi.  Whilst the most basic “hello world” application (surprisingly!) can be copied from a Sheevaplug-type system to a Raspberry Pi, it’s less straightforward for nontrivial applications.

 

I see:

   “./myprogram: error while loading shared libraries: unexpected PLT reloc type 0x12”

 

 http://wiki.debian.org/ArmHardFloatPort discusses the differences between  armel and armhf – crucially the ABI is different – hence the incompatibilities.

The solution?  

As an interim workaround, running the older Debian Squeeze distro might make life easier (and permit binary sharing in the short term).  It also sounds like it may be possible to install the armel versions of the same libraries in parallel with the armhf versions on the same system (and presumably carefully manipulate LD_LIBRARY_PATH when running armel binaries) – but that sounds like a bit of a maintenance headache. Longer term I want to be running Raspbian and get the performance benefits of moving to armhf anyway.

The pragmatic answer (for my use case, anyway) is, therefore, to recompile.