Tim Child

As part of my on going effort for realtime web updates on one of our applications I needed to install RabbitMQ HEAD (That is the development head) with the RabbitMQ STOMP adaptor. Talking on IRC channel it was recommended to me to install from source, but unfortunately the documentation is out of date. So the following will do it cleanly:

Updated: The following will create a Debian style package and install (replace ** with the version numbering that you wish to use:

Activating the STOMP plugin:

Configuration file:

Restart to activate (the activation script for plugins is depreciated):

And you should have a working RabbitMQ on Ubuntu with a STOMP adaptor.

Wake-on-lan is incredibly useful for those scenarios where you have more than one machine on a network, but you don’t always want to have them running but they are needed sometimes.

To setup, make sure that the Motherboard and NIC support is there from your manufacturer. Sometimes it has to be enabled, such as making sure that it uses S3 for shutdown, and that PCI wake is supported.

Next you need to check support from the operating system, I am using Ubuntu 10.04, but this should work for other operating systems. Install ethtool, and then check against the ethernet adapter (eth0 in my example).

If support is enabled, but it is turned off you will see:

So we turn it on:

Now we need to make sure that its always enabled everytime we restart:

And in that file:

Now make sure that its put into the correct runlevels:

And that is it. It should be supported that you can wake the machine from another computer/server using your favourite wakeup utility ( such as wakeonlan ).

I always have this problem when moving VMWare images of Ubuntu, the most recent of a 10.04 LTS Server. Whenever you move or copy a VMWare image it assigns a new Mac address and Ubuntu starts without properly bringing up the interface.

Really annoying when you are using VMWare server without a console.

To make it grab the IP Address again, simply remove the rule:

Then restart.

Of course before you move the image you could remove the rule and not have them problem.

I am normally using Debian, Ubuntu or even Suse for deploying Django, but a recent customer needed to deploy on Red Hat Enterprise Server 5.

We decided beforehand to test deployment on RHEL5 and also on CentOS 5.4 and so these instructions should work for both environments. NginX will be used as the webserver.

The first thing I like to do is to upgrade the repository and add EPEL. This wasn’t needed I found on the RedHat box I was using, but was needed on CentOS but your mileage might vary. It should be noted that we made the system as up to date as possible with patches and yum updates.

I won’t be covering the database setup, it is assumed that this is already setup and done. I also won’t be covering the actually placing of the Django application anywhere.

Python 2.4 ships with both RHEL5 and CentOS 5 and is needed for the packaging environment YUM so I would advise not to replace it but just compile and install 2.5.5 (or 2.6) next to it.

Now we need to build and install NginX. I choose this primarily because of my experience with it, (I have used Apache2 a lot but its archaic ) and because of its speed.

There is a decent RedHat init.d script here: http://wiki.nginx.org/RedHatNginxInitScript, but remember that I have changed the installation location above so you will need to change the location in that script of nginx from /usr/sbin/nginx to /usr/local/sbin/nginx

You will also need a nginx.conf configuration script for /etc/nginx/ or you could roll your own using sites-available, sites-enabled pattern. I will attach the script soon.

Now with Python 2.5 installed we can install Django and other requirements:

I am using easy_install here as that is the most widely used tool, but pip with a requirements file is a better solution.

Now we need a database adapter. I am using PostgreSQL 8.4.2, if you are using MySQL, Oracle or some other database you will need to follow the recommended route for the Python adapter.

Change the location of pg_config:

And now install:

Then you need to install your application. This is really specific to your needs. I choose to install the files in /opt/cantemo/application-name as that is specific to our solutions, but RedHat style might mean that you wish to install somewhere else.

Lastly you will want to have your application start easily and also make sure that it starts if the machine ever reboots. To do this I am going to install the start-stop-daemon that is used on Debian based Linux distros on Redhat. I read some threads that it will but there is no ETA on that.

You should download the initd script for Django from http://code.djangoproject.com/wiki/InitdScriptForLinux. Change the RUN_AS user to the user on RedHat that you are going to use for running Nginx. By default this is apache.

Lastly make sure that your application directories have the correct user permissions but you should be able to start everything by issuing the following commands:

Eric Florenzano posted a nice tutorial on deploying django using FastCGI so also check that out, but I didn’t have much luck with daemontools on CentOS, and didn’t bother trying on RedHat. I suggest instead using start-stop-daemon. Check it out for other hints and tips though, particularly on prefork vs. threaded, pip, and more nginx configuration tips.

I have been using Hudson as a continuous integration server for a short while now and I am super impressed. I have it running on Debian and is really quite feature-full.

One thing that I did have a problem with was with the standard Debian 5 Java environment there was a problem using TLS for mail it seemed, and I didn’t just want to send stuff to gmail’s SMTP server all the time so I configured a local Postfix SMTP relay on another server.

This guide, Send Mail Postfix Through Gmail’s SMTP On A Ubuntu LTS Server helped a lot – but be sure to read the comments as there are some helpful hints.

So now I have it. Hudson running and sending email through my relay to my gmail accounts.

More information on Hudson soon.

After posting up the last entry about SSH I noticed that I had a problem with my Permalinks. Seems that there is some nasty little injection problem with WordPress that changes the Permalinks with the addition of.

I am following the suggestions here:

http://blog.4rev.net/2009-09/wordpress-hacked-eval-base64_decode-_serverhttp_referer/

And it seemed to work.

This is a tip that I have used on OS X and on Linux, which I presume works on other *nix and BSDs using SSH.

Basically in the .ssh folder in your home directory you can create a file called config with which you can put all sorts of configuration information for your ssh client but the real benefit for me was to use this to give extra information to hosts such as defining a different port number to connect on. For instance:

This means that instead of typing:

I can type:

No need for nasty aliases in the shell or anything like that. This also works for the sshfs program on the Mac that makes use of MacFuse. Yes that’s right you can use different ports with SSHfs.

You can also change a much wider range of parameters than I have shown here, but often its probably better to introduce them on the server. But here is an example and have a look under the options flag in the Man page for SSH

I have been looking for a good way of keeping track of changes to /etc and with Ubuntu 9.04 Server I see that they have rolled in support for etckeeper (using bzr as the default).

This little util allows the use of version control (bzr, hg or git) to track changes to /etc and with the Ubuntu version integrates with apt and dpkg so that new package installs are tracked.

To install just install the following, it will take care of the dependancies:

The Initialize the repository:

And do a commit of the files to the repository.

After each change to file(s) in /etc

Now I just have to back up the files from the repository for a good way of rolling back and forth between versions. Probably onto a USB key

Over the past week or so (slowed down by the damn flu) I have been building a new server for home. Its going to have the following duties:

• Backup server (with Apple Time Machine)
• File server
• NNTP server
• iTunes server
• Database server (mainly PostgreSQL)
• VMWare server

The hardware is mounted in rackmount chassis with space for 12 drives, 6 of which will be populated straight away, has a 64bit processor and will have 3Gb of RAM (The maximum on this old hardware).

I have installed Ubuntu 9.04 Server edition on it, and I must say that it went very smoothly except for the fact that Python 2.5 on Ubuntu 9.04 is a pain, often breaking. Here are some useful commands:

Having two installations of different version of python and switching between them:

To undo:

To force a change of version:

Then this will be the main server in the house, with lightweight front ends (This will have over 4Tb of RAID with expandability to 12TB). My old book will retire until I think of a good use for its out of date hardware.

There is a really interesting article over here about ubuntu 9 compared to Vista and Windows 7.

http://tuxradar.com/content/benchmarked-ubuntu-vs-vista-vs-windows-7

They compared installation time. Ubuntu was faster.
Mouse clicks in the installation: Ubuntu had less.
Disk space used: Ubuntu used less.
Bootup: Microsoft was faster, Windows 7 being the leader.
Shutdown: Linux was faster.
IO: Linux was faster.
Python: Windows just about edged it.

In the real world it probably doesn’t matter, the vast majority of users will continue on with a Microsoft operating system because the software they want to run and have supported by their local IT team will make this easier. Interesting followup here:

http://www.tuxradar.com/content/linux-vs-windows-7

As an OS X user the “improvements” to Windows appearance is laughable still.