Posts Tagged software development

Using Gerty for Cisco config automation

I’m developing the Gerty software since about two years already, and it needs a bit of an effort to publish the final release. Anyway, it’s completely usable and production ready.

Here I placed a new example based on a real-life use case: a few hundred Cisco routers need a context-dependent configuration update.

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Moving from Subversion to Git

Many teams have their internal scripts in private SVN repositories. It works quite well for most cases. Here’s a short overview of why you may want a transition to Git:

  • Git is distributed. You have the whole history of the project in your local directory. Also your work is independent from central server availability.
  • Branching and merging is in the nature of Git:  whatever new activity you start, you can spin off a new branch and do your commits without disturbing the production code. After testing, you merge your changes into the master branch easily.
  • Bigger choice of transport: Git allows to communicate via SSH, HTTP, its own Git protocol, or by simply archiving and copying your repository if there’s no direct connection to the central server. With SSH transport, you can easily work around strict firewall policies: the pull and push commands are somewhat symmetrical, so if you can’t access the central server for pushing, you can probably pull from your work machine to some intermediate location, and then push to the central server. The possibilities are countless.
  • You can keep all your server or application configuration in Git repositories. This allows you to restore the configuration quickly after an unsuccessful change, and you’re not dependent on the central server availability.
  • You can have as many central servers as you need for your workflow (for example, I use two public repositories for Torrus).

But of course, Git is different, and it needs a bit of learning.  The whole workflow has to be adapted, as well as habits:

  • Your commits don’t go to the central server until you explicitly push them.
  • There is no such thing as revision number. You have SHA hash strings instead.
  • You are encouraged to do more frequent commits, or group them differently. As you do your commits locally without disturbing anyone, you can control the granularity of your commits in a much more flexible way. You can also undo your commits before they are pushed to the central server.

There are many ways to organize your Git repositories:

  • If you work alone and your machine is backed up, you may not even need a central repository.
  • At Github  you can have unlimited public repositories, or a number of private repositories at a cost.
  • Gitorius is a relatively new service, analogous to Github. Also Sourceforge and many other open-source project hosting services offer Git hosting.
  • Gitolite is a nice software that allows you to set up your own Git hosting server easily, with SSH key authentication for multiple users, and access rights. Debian and other packages are available.

UPD: some interesting comments at Hacker News

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DENOG3 presentation

I made a presentation at the DENOG3 meeting last week and covered the following Perl-based open-source software products for network management and monitoring:

  1. Torrus, a well-established and mature software for massive SNMP polling and performance monitoring.
  2. Gerty, a new project for network automation. Any tasks on the network devices which need any interaction and automation, are targeted by the tool. The first release is expected soon.
  3. Mooxu, a new project which is currently in its early design phase. The product will provide a platform for distributed network testing and monitoring (eventually it may replace Torrus).

The slideshow PDF is available at the meeting agenda page, and also a video will be available soon.

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PC emulated in Javascript

Amazing stuff: the guy has emulated an x86 CPU in JavaScript!

http://bellard.org/jslinux/tech.html

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Gerty, the RANCID replacement

started a new project about a month ago, and the first proof of concept is already useable:

http://github.com/ssinyagin/gerty

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