Just a small bash snippet for those cases where, for example, a command returns AWS instance IDs but not the matching DNS names or an IP addresses. The function id2dns, that you can add to your .bashrc file, will do the translation for you. In order to use the function you will:
- ensure you have the aws CLI installed and functional;
ensure you have jq command available;
- ensure you have valid AWS credentials set, so that your aws CLI will work.
Update 2020-08-14: jq not needed any more
This is mostly a note to self. When I need an EC2 instance to run a quick test, it may be overly annoying to provision one through the web console, or it may feel a bit overkill to do that using large frameworks like terraform. Using the AWS command line is just fine, if you know what command to run with which parameters, and it pays off quickly if, to run your tests, you use the settings often (AMI, subnet, security groups…) or if during the same test session you need to scrap and rebuild test instances a few times. Here is an example on how to do so with the AWS command line client.
Say you have access to two separate AWS accounts, and say you have EC2 instances running in a certain region and availability zone, e.g eu-west-1a, in both accounts. Today I learned to my greatest surprise that, despite the same name, they may actually be two totally different locations. Intrigued? Read on!
I’ll tell you a personal story, hoping that it will encourage as many of you as possible to dust off some old computer you have in a storage of yours to help finding a cure against COVID-19 and, hopefully, many other diseases. If that sounds interesting, please read on.
I have published a small update to cf-keycrypt, so that it’s now easier to compile the tool on Debian systems and it’s compatible with CFEngine 3.15. You can find it here.
For those who don’t know the tool, I’ll try to explain what it is in a few words. The communication between CFEngine agents on clients and the CFEngine server process on a policy hub is encrypted. The key pairs used to encrypt/decrypt the communication are created on each node, usually at installation time or manually with a specific command. cf-keycrypt is a tool that takes advantage of those keys to encrypt and decrypt files, so that they are readable only on the nodes that are supposed to use them. The fact that the keys are created on the nodes themselves eliminates the need to distribute the keys securely.
cf-keycrypt was created years ago by Jon Henrik Bjørnstad, one of the founders of CFEngine (the company). The code has finally landed the CFEngine core sources as cf-secret, but it’s not part of the current stable releases. I had an hard time trying to compile it, but I made it with good help from the CFEngine help mailing list. I decided to give the help back to the community, publishing my updates and opening a pull request to the original code. Until it’s merged, if it ever will, you can find my fork on my github.
After five years after the release of cf-deploy v3, I have just released cf-deploy v4. This version of cf-deploy fixes a number of shortcomings that made their way up to this point and that I wasn’t able to see until recently. It is now more flexible and easier to configure than it ever was. In particular, the documentation is way more comprehensive, covering installation, configuration and usage. The documentation also covers some of the internals, that will allow the hardcore user to fine tune the tool to better suit their needs.
You will find cf-deploy on github, as always. Enjoy!
Recently, while testing a configuration of Linux on a Lenovo laptop, I messed up. I had rebooted the laptop and there were some leftovers around from an attempted installation of the proprietary Nvidia driver. The system booted fine and was functional, but those leftovers where enough to make the screen go blank. The fix is easy, if you can enter the system in some other way: log in and remove anything related to the Nvidia driver. But unfortunately the only way to log in was from the console, so I was “de facto” locked out.
The first attempt to get out of the mud was to force a reboot of the system and in rescue mode. The system booted well, but after I typed the root password the boot process went a bit too far, loaded the infamous leftovers of the driver and here we go again, with a blank screen.
This article is about using configuration management to install software on your own computers (e.g. your laptops, or the computers used by your family and relatives) and how the complexity of this task is easy to overlook, no matter if you are a newbie or an expert.
If you already know about configuration management and how it makes sense to use it at a small scale like, again, your own computers or your family’s, you can just skip at the section “New job, new setup”.
If you already know about configuration management and you are asking yourself why it should make sense to use it at a small scale, I suggest that you start a section earlier, at Personal configuration management”.
If you are new to configuration management, or you wonder what could be difficult in installing software on a set of systems, I suggest that you read the whole article.
In any case, happy reading!
Having recently started to work for Riks TV, I got a new laptop to install with my favourite Linux distribution: Debian. The laptop is a Lenovo ThinkPad P1 Gen2. It’s a very nice laptop, quite powerful and fast, with a large screen and way lighter than the Lenovos I have owned before through my previous employers (Opera Software and Telenor Digital).
That’s all great, but on the other hand my previous story with Lenovo laptops has never been problem-free, and I was sure this one was no exception. Alas, I was right. So I decided to write a few notes about the installation, for myself and for anyone who wants to install Debian on this laptop. These won’t be detailed, walk-through installation instructions, but more of a high-level checklists.
Last month I wrote a new post, namely: Building a simple, resilient, cheap network service with AWS. Now that AWS’ billing cycle for November is complete we can ask ourselves how cheap was that “cheap” in the article, and give an answer. The cost is not exact to the cent, due to the presence of a a stopped instance I am keeping around, but will still be good enough.
To summarise, the article described how to set up a service on spot instances, thus saving on the EC2 cost. We want to understand if we really saved money, and if there are opportunities to save even more. If you haven’t read the previous post, it’s probably a good time to do it now. If you did, let’s go and check the bill.