Category Archives: Apache

OpenClinica Tomcat Error When Setting JAVA_OPTS on Ubuntu 10.04

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I’ve setup OpenClinica a number of time and never really touched the JAVA_OPTS for Tomcat because I’ve never really had any issues. On the OpenClinica Installation Documentation it states that the JVM performs well when using the following JAVA_OPTS

https://docs.openclinica.com/3.1/installation/installation-linux#content-title-5460

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export JAVA_OPTS="$JAVA_OPTS   -Xmx1280m -XX:+UseParallelGC -XX:ParallelGCThreads=2 -XX:MaxPermSize=180m -XX:+CMSClassUnloadingEnabled"

However, if you’re running Ubuntu 10.04 LTS, you will receive an error when modifying the /etc/default/tomcat6 JAVA_OPTS.

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Conflicting collector combinations in option list; please refer to the release notes for the combinations allowed

The two options that cause this error are “-XX:+UseParallelGC -XX:ParallelGCThreads=2″, if you remove these then the errors go away. Looking into this further, I’ve found some documentation but not much. The commands are related to garbage collection, and the following article sheds some light on the above two commands as well as “-XX:+UseParNewGC”

http://stackoverflow.com/questions/2101518/difference-between-xxuseparallelgc-and-xxuseparnewgc

Upon remove the two recommended options and adding ”-XX:+UseParNewGC” tomcat6 starts without error.

If anyone has any information on why this is, it would be great to know.

Apache Tomcat Native library Not Found Error on Ubuntu

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Sometimes you might get the following error message in your logs for your Tomcat instance under Ubuntu.

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The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found

To fix this issue, simply run the following command to install the appropriate library.

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apt-get install libtcnative-1

The error should go away!

Apache dDoS “killapache” Sends Malformed GET Requests

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There is a bug in certain versions of Apache that is susceptible to a dDoS using malformed GET requests. You can find more information about “killapache” at the following site.

http://www.pentestit.com/2011/08/25/killapache-ddos-tool-freezes-apache-web-server/

 

There is no patch, however their is a work around for this bug which is provided below. In Ubuntu or Debian create a new file “/etc/apache2/conf.d/killapache-fix” and place the following code

 

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# Drop the Range header when more than 5 ranges.
# CVE-2011-3192
SetEnvIf Range (,.*?){5,} bad-range=1
RequestHeader unset Range env=bad-range

# optional logging.
CustomLog logs/range-CVE-2011-3192.log common env=bad-range

You may need to install the “headers” module, which can be done by typing “a2enmod headers” and then you should be able to reload apache without errors.

 

WordPress Permalink Sub-Directory 404 Error Weirdness

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I didn’t really know what to put for the title of this post, but hopefully the content makes more sense and gets indexed properly and found by people looking for this specific information.

The problem is when you install WordPress and setup Permalinks which uses a .htaccess file for Apache. The .htaccess make cause problems with other applications or HTML files you have in sub-directories in your document root.

The fix? It’s simple, just view this blog post. It explains to fix the problem you simply place “ErrorDocument 401 default” at the top of your .htaccess file and everything is resolved. Your WordPress installation still generates 404 pages, but now sub-directories work correctly.

http://www.geoffblog.com/2009/04/wordpress-htaccess-clashes-with-sub.html