From AWS instance IDs to private DNS names

github-logoJust 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.

Enjoy!

Update 2020-08-14: jq not needed any more

 

cf-deploy: easier deployment of CFEngine policies

Update: this article refers to the very first version of cf-deploy. For the latest release, check the github repository.


GitRepoStructureIn my latest post “git repository and deployment procedures for CFEngine policies” I explained how we structured our git repository for CFEngine policies, and how we built a deployment procedure, based on GNU make, to easily deploy different projects and branches from the same repository to the policy hubs. Please read that post if you haven’t yet, as this one is not going to make much sense without it.

The make-based deployment procedure worked pretty well and was functional, but still had annoyances. Let’s name a few:

  • the make command line was a bit long and ugly; usually it was something like:
    make -C /var/cfengine/git/common/tools/deploy deploy PROJECT=projX BRANCH=dev-projX-foo SERVER=projX-testhub
  • the Makefile was not optimized to deploy on more than one server at a time. To deploy the same files on several hubs, the only solution was to run make in a cycle several times, as in
    for SERVER in projX-hub{1..10} ; do make -C /var/cfengine/git/common/tools/deploy deploy PROJECT=projX BRANCH=dev-projX-foo SERVER=$SERVER ; done
  • deploying a project on all the policy hubs related to that project required one to remember all of the addresses/hostnames; forget one or more of them, and they would simply, hopelessly left behind.

At the same time, there were a few more people that were interested in making tiny changes to the configurations via ENC and deploy, and that long command line was a bit discouraging. All this taken together meant: I needed to add a multi-hub deployment target to the Makefile, and I needed a wrapper for the deployment process to hide that ugly command line.

For first, I added to the Makefile the functionality needed to deploy on more than one hub without having to re-create the temporary directory at every run: it would prepare the files once, deploy them as many times as needed, and then wipe the temporary directory. That was nice and, indeed, needed. But the wrapper couldn’t wait any longer, and I started working on it immediately after. That’s where cf-deploy was born.

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