Writing on Unix, Debian, Perl, Java and everything else.https://www.davidpashley.com/https://www.davidpashley.com/2016/01/18/nullpointerexceptions-in-xerces-j/https://www.davidpashley.com/2016/01/18/nullpointerexceptions-in-xerces-j/Xerces is an XML library for several languages, but if a very common library in Java. I recently came across a problem with code intermittently throwing a NullPointerException inside the library: You may also find the NullPointerException in ParentNode.nodeListGetLength() and other locations in ParentNode. Debugging this was not helped by the fact that the xercesImpl.jar is stripped of line…Mon, 18 Jan 2016 14:40:36 GMTjavaxerceshttps://www.davidpashley.com/2014/04/23/working-development-servers/https://www.davidpashley.com/2014/04/23/working-development-servers/I can't believe that this is not a solved problem by now, but my Google-fu is failing me. I'm looking for a decent, working extension for Chrome that can redirect a list of hosts to a different server while setting the Host: header to the right address. Everything I've found so far assumes that you're running the servers on different urls. I'm using the same URL on different servers and don't…Wed, 23 Apr 2014 15:31:45 GMTcomputinghttps://www.davidpashley.com/2014/04/16/bad-password-policies/https://www.davidpashley.com/2014/04/16/bad-password-policies/After the whole Heartbleed fiasco, I've decided to continue my march towards improving my online security. I'd already begun the process of using LastPass to store my passwords and generate random passwords for each site, but I hadn't completed the process, with some sites still using the same passwords, and some having less than ideal strength passwords, so I spent some time today improving my…Wed, 16 Apr 2014 01:03:01 GMTcomputinghttps://www.davidpashley.com/2013/09/23/new-chapter/https://www.davidpashley.com/2013/09/23/new-chapter/It's been a while since I posted anything to my personal site, but I figured I should update with the news that I'm leaving Brighton (and the UK) after nearly nine years living by the seaside. I'll be sad to leave this city, which is the greatest place to live in the country, but I have to opportunity to go explore the world and I'd be crazy to let it pass me by. So what am I doing? In ten short…Mon, 23 Sep 2013 07:20:58 GMTUncategorizedlifehttps://www.davidpashley.com/2011/01/29/multiple-crimes/https://www.davidpashley.com/2011/01/29/multiple-crimes/WTF? (via Nuxeo)Sat, 29 Jan 2011 13:35:20 GMTmysqlhttps://www.davidpashley.com/2010/03/17/digital-economy-bill-letter/https://www.davidpashley.com/2010/03/17/digital-economy-bill-letter/I have just sent the following email to my MP, David Lepper MP, outlining my concerns about the Digital Economy Bill. I urge you to write to your MP with a similar letter. Open Rights Group's guide to writing to your MPWed, 17 Mar 2010 12:35:53 GMTpoliticshttps://www.davidpashley.com/2010/03/07/mod_fastcgi/https://www.davidpashley.com/2010/03/07/mod_fastcgi/Has anyone managed to get a standard version of modfastcgi work correctly with FastCGIExternalServer? There seems to be a complete lack of documentation on how to get this to work. I have managed to get it working by removing some code which appears to completely break AddHandler. However, people on the FastCGI list told me I was wrong for making it work. So, if anyone has managed to get it to…Sun, 07 Mar 2010 23:02:49 GMTapachehttps://www.davidpashley.com/2010/02/25/reducing-coupling/https://www.davidpashley.com/2010/02/25/reducing-coupling/In the past, several of my Puppet modules have been tightly coupled. A perfect example is Apache and Munin. When I install Apache, I want munin graphs set up. As a result my apache class has the following snippet in it: This should make sure that these three plugins are installed and that munin-node is restarted to pick them up. The define was implemented like this: (Note: this is a slight…Thu, 25 Feb 2010 09:30:18 GMTpuppethttps://www.davidpashley.com/2009/12/22/grails-1-2-maven/https://www.davidpashley.com/2009/12/22/grails-1-2-maven/Because I couldn't find the information anywhere else, if you want to use maven with Grails 1.2 snapshot, use:Tue, 22 Dec 2009 23:01:35 GMTjavahttps://www.davidpashley.com/2009/12/08/printer-conversation/https://www.davidpashley.com/2009/12/08/printer-conversation/I just had the following conversation with my linux desktop: Me: "Hi, I'd like to use my new printer please." Computer: "Do you mean this HP Laserjet CP1515n on the network?" Me: "Erm, yes I do." Computer: "Good. You've got a test page printing as we speak. Anything else I can help you with?" Sadly I don't have any alternative modern operating systems to compare it to, but having done similar…Tue, 08 Dec 2009 15:42:03 GMTlinuxhttps://www.davidpashley.com/2009/10/13/tarballs/https://www.davidpashley.com/2009/10/13/tarballs/This entry was originally posted in slightly different form to Server Fault If you're coming from a Windows world, you're used to using tools like zip or rar, which compress collections of files. In the typical Unix tradition of doing one thing and doing one thing well, you tend to have two different utilities; a compression tool and a archive format. People then use these two tools together to…Tue, 13 Oct 2009 10:57:56 GMTlinuxbzip2gzipserverfaulttarhttps://www.davidpashley.com/2009/10/11/mod_proxy-or-mod_jk/https://www.davidpashley.com/2009/10/11/mod_proxy-or-mod_jk/This entry was originally posted in slightly different form to Server Fault There are several ways to run Tomcat applications. You can either run tomcat direcly on port 80, or you can put a webserver in front of tomcat and proxy connections to it. I would highly recommend using Apache as a front end. The main reason for this suggestion is that Apache is more flexible than tomcat. Apache has many…Sun, 11 Oct 2009 11:53:33 GMTtomcatserverfaulthttps://www.davidpashley.com/2009/10/10/copyright/https://www.davidpashley.com/2009/10/10/copyright/To make things explicitly clear, my blog is copyrighted and licensed as "All rights reserved". It even says that at the footer of every page. That means you may not redistribute any content without my permission. Yes, this means you, Ross Beazley. I may allow aggregation sites to redistribute my content, but the only sites where I have given explicit permission are Planet Debian and Planet BNM. I…Sat, 10 Oct 2009 19:57:05 GMTmetahttps://www.davidpashley.com/2009/10/10/name-based-https/https://www.davidpashley.com/2009/10/10/name-based-https/This entry was originally posted in slightly different form to Server Fault There are two methods of using virtual hosting with HTTP: Name based and IP based. IP based is the simplest as each virtual host is served from a different IP address configured on the server, but this requires an IP address for every host, and we're meant to be running out. The better solution is to use the Host: header…Sat, 10 Oct 2009 08:17:21 GMTcomputinghttps://www.davidpashley.com/2009/09/01/gitosis/https://www.davidpashley.com/2009/09/01/gitosis/While git is a completely distributed revision control system, sometimes the lack of a central canonical repository can be annoying. For example, you might want to make your repository published publically, so other people can fork your code, or you might want all your developers to push into (or have code pulled into) a central "golden" tree, that you then use for automated building and…Tue, 01 Sep 2009 17:38:18 GMTlinuxhttps://www.davidpashley.com/2009/08/18/nginx-mongrel/https://www.davidpashley.com/2009/08/18/nginx-mongrel/If you've not heard of Puppet, it is a configuration management tool. You write descriptions of how you want your systems to look and it checks the current setup and works out what it needs to do to move your system so it matches your description. The idea is to write how it should look, not how to change the system. Puppet uses a client (puppetd) that talks to the central server (puppetmaster)…Tue, 18 Aug 2009 22:36:36 GMTpuppethttps://www.davidpashley.com/2009/08/06/svn-up/https://www.davidpashley.com/2009/08/06/svn-up/Sometimes you need to review what exactly doing an svn up will do. Fortunately, you can do a couple of things to find out. The first is use svn status -u to find out what files have changed: Here we can see that four files were changed since their current revision of 1338. We can also see that tomcat/files/server.xml is up to date against the repository, but has local modifications. This is all…Thu, 06 Aug 2009 08:48:00 GMTlinuxsubversionhttps://www.davidpashley.com/2009/07/24/efficient-find/https://www.davidpashley.com/2009/07/24/efficient-find/Recently, I've seen a lot of suggestions along the lines of: This is incredibly inefficient, because for each and every matching file, ls will be executed. Fortunately, we can do better by using xargs. xargs takes a list of lines from stdin and uses them to build up a command line. It takes special care to not exceed the maximum command line length by splitting the input up into multiple commands…Fri, 24 Jul 2009 23:37:54 GMTlinuxhttps://www.davidpashley.com/2009/06/15/copying-files-with-netcat/https://www.davidpashley.com/2009/06/15/copying-files-with-netcat/When you want to copy files from one machine to another, you might think about using scp to copy them. You might think about using rsync. If, however, you're trying to copy a large amount of data between two machines, here's a better, quicker, way to do it is using netcat. On the receiving machine, run: On the sending machine you can now run: You should find that everything works nicely, and a…Mon, 15 Jun 2009 13:51:51 GMTlinuxnetcatrsyncscphttps://www.davidpashley.com/2009/06/10/table_sizes/https://www.davidpashley.com/2009/06/10/table_sizes/Ever wanted to find out how much diskspace each table was taking in a database? Here's how: Table size is the size for the current data. Total table size includes indexes and data that is too large to fix in the main table store (things like large BLOB fields). You can find more information in the PostgreSQL manual. Edit: changed to use pgsizepretty(), which I thought existed, but couldn't find…Wed, 10 Jun 2009 10:42:45 GMTpostgresqlPostgreSQL