Archives For March 2012

Lately I’ve been coding to automate the deployment of Virtual Machines that will run in our cloud. It’s inspired by blogs and code from Jason Hancock but implemented in a different way to meet our specific needs. Since CloudStack has a very flexible API, you can make it do anything you want. It works pretty cool so far.

From a command line script we can deploy a new VM with a certain “role”. This role has a name, like “web server” or “test-vm-db” and contains the OS template name, the datacenter name, the networks to connect to, the hardware offering (CPU/Memory/Disk) and the account and domain to use. These are all CloudStack specific settings. When calling the deployVirtualMachine() API command, CloudStack will create a VM with exactly these specs. We use a simple php cli script to add a new server, like this:


Since it is in a specific domain (defined by the role), other users in that domain can “see” and work with the new VM immediately. When you deploy for a client, they will “see” the new VM like this:

When the VM boots, it is receives its role name, “web server” for example, and sends this info to Puppet. This way, Puppet knows how to configure the new VM. It will do so and when it’s finished you have an exact same “web server” as the others. Run the script again and you’ll have another one. Puppet does not only do initial configuration, it will make sure the configuration stays consistent across the all servers it manages. When you want to change a setting, Puppet distributes it and makes sure it’s the same on all servers. All automatically!

Imagine the power behind this concept. All of a sudden you can create a script that can deploy a new web server in just minutes. Now even the loadbalancer itself can spin up a new web server to handle the higher load it receives. Or destroy a web server when there are too many idle web servers. That’s what you call elastic!

What you need to build this yourself is:
1. PHP CloudStack Client (to talk to CloudStack from PHP)
2. CloudStack API docs
3. Script to grab meta-data when VM has booted

Please see Jason Hancock‘s blog for some working examples of how he implemented it. As I said, CloudStack’s API is very flexible. But you can even extend the API, if you want to go further. Thanks for the inspiration Jason!

Today while I was running I realized I’ve been doing a lot of coding lately. Coding our new infrastructure to be exact. I remembered Kris Buytaert’s talk about DevOps back in February when I was in Antwerp. One of the key statements is that there are ‘sysadmin coders’ and not ‘sysadmins’ and ‘coders’. The only way to achieve great results, is when these two work together and communicate with each other. The idea’s behind this are called DevOps. IT Operations starts using code to manage configurations and infrastructure instead of doing it by hand over and over again. Thanks to CloudStack and Puppet this is now possible. Ideally, you would not have two groups, but one. Stephen Nelson-Smith from describes it like this:

So, the Devops movement is characterized by people with a multidisciplinary skill set – people who are comfortable with infrastructure and configuration, but also happy to roll up their sleeves, write tests, debug, and ship features. These are people who making connections, because they can – because they have feet in multiple camps, they can be ambassadors, peace makers, facilitators and communicators. And the point of the movement is to identify these, currently rare, people and encourage them, compare ideas, and start to identify, train, recruit and popularize this way of doing IT.

More on Stephen’s blog..

I didn’t realize back then what this would mean because I was focused on CloudStack and the tools around it. But it is not only about the tools, it’s the way you look at managing infrastructure and development. What we’re doing looks like DevOps but we’re not there yet ;-). In the coming weeks I’ll spend some more time reading about DevOps to see how we can implement this in our organization. Because I really believe this is the way to go..

Remote Linux systems usually have to be available all the time. Although Linux is rock solid and stable, an occasional crash can occur. For example when there’s a problem with hardware or software. The last thing you want, is that a Linux server got a kernel panic and then waits forever for someone to reboot it.

Of course there’s monitoring, and there are APC’s too, which can reboot the server. This is like pulling the plug. It usually takes some time for monitoring to notify a sysadmin and then for the sysadmin to reboot the server. And, when using IPMI devices (especially the older ones that share a network connection with the server), a kernel panic could make them unavailable, too. I’ve had that on many occasions. Then you end up driving to the data center or call someone to reset the server. I hate that 😉

In our setup, most servers are in clusters. This means losing one server should not be a problem. But you still want a server to be available again as soon as possible, to be able to handle future problems.

There’s a way to configure Linux to reboot automatically, say 10, seconds after a kernel panic occurs. This will quickly and automatically have the server up again. Should rebooting not help, then bad luck and there’s probably some failing hardware part. You’ve then to drive to the data center anyway.

So, how to do that? Well, there are several options to set this parameter. To test this out, use this command:

/sbin/sysctl -w kernel.panic=10

Note that this setting will not survive a reboot. If you want it to remain active, add this line to /etc/sysctl.conf:


To check the current setting, issue:

cat /proc/sys/kernel/panic

It is wise to implement some sort of monitoring on reboots or uptime. You definitely want to read the logfiles and find out what exactly happened that led to the kernel panic.

Today is a very nice day with a lot of sun shine. This morning I decided to go for a run, to get rid of the stress and to enjoy being outside. Just running for some time makes me calm and relax again. I love that feeling!

I haven’t been running for almost a year. Today I took my Garmin Forerunner 305 with me. The nice thing is that the device has a GPS chip and can track many things, like distance, pace, heartbeat, calories etc. When I got home, I uploaded the run data to the MapMyRun website. It produces these nice images:

As you’ll probably see the distance and pace are not quite impressive yet 😉 Over time it should get better.. and as long as it makes me feel good it’s ok with me!

When working in shells, it’s very useful to have syntax highlighting. In vim it’s just ‘:sy on’ and you’re done. For those of you using GNU Nano, I’ll show you how to enable syntax highlighting as well.

To start, we’ll need some files which tell nano what to display in what color. Here is an example of such a file for PHP:

nano /usr/share/nano/php.nanorc

syntax "php" "\.php|\.inc$"
color white start="<\?(php)?" end="\?>"
color magenta start="<[^\?]" end="[^\?]>"
color magenta "\$[a-zA-Z_0-9]*"
color brightblue "\->[a-zA-Z_0-9]*"
color cyan "(\[)|(\])"
color brightyellow "(var|class|function|echo|case|break|default|exit|switch|if|else|elseif|@|while|return|public|private|proteted|static)\s"
color brightyellow "\<(try|throw|catch|operator|new)\>"
color white "="
color green "[,{}()]"
color green "=="
color brightgreen "('[^']*')|(\"[^"]*\")"
color yellow start=""
color yellow start="/\*" end="\*/"
color yellow start="#" end="$"
color yellow "//.*"

Then we tell nano where this file is to be found:

nano /etc/nanorc

And add this line:

## PHP
include "/usr/share/nano/php.nanorc"

You then should see this when editing a PHP file with nano:

You can do the same for Bash files. Here’s the config file:

nano /usr/share/nano/sh.nanorc

syntax "sh" "\.sh$"
icolor brightgreen "^[0-9A-Z_]+\(\)"
color green "\<(case|do|done|elif|else|esac|exit|fi|for|function|if|in|local|read|return|select|shift|then|time|until|while)\>"
color green "(\{|\}|\(|\)|\;|\]|\[|`|\\|\$|<|>|!|=|&|\|)"
color green "-[Ldefgruwx]\>"
color green "-(eq|ne|gt|lt|ge|le|s|n|z)\>"
color brightblue "\<(cat|cd|chmod|chown|cp|echo|env|export|grep|install|let|ln|make|mkdir|mv|rm|sed|set|tar|touch|umask|unset)\>"
icolor brightred "\$\{?[0-9A-Z_!@#$*?-]+\}?"
color cyan "(^|[[:space:]])#.*$"
color brightyellow ""(\\.|[^"])*"" "'(\\.|[^'])*'"
color ,green "[[:space:]]+$"

It’s pretty easy to customize if you want. So now you never have to edit scripts without syntax highlighting again!