From their blog:
Cumulus Linux is a Linux distribution which has support for networking co-processors. It is not simply a networking device which uses Linux as a base OS. Linux is the OS. All of the device’s interfaces are standard Linux interfaces. So when you type “ifconfig”, you’ll see all of the interfaces, just like on a Linux server. Want to bring a link up? You can use “ip link set”. “brctl” sets up and configures bridges. Standard open-source routing protocol suites, like Quagga, can be used.
This also means that you can do things like you would on any other Linux device, like mount remote file systems, or install and use standard monitoring, administration, and reporting tools. Puppet, collectd, Nagios, bwm-ng, and most other Linux-based tools can be easily downloaded and installed using apt-get. You could even run custom scripts written in Python, or Perl, or C and, for example, put them in a crontab to periodically run. And since the network co-processor is handling all of the datapath forwarding functions, the switch operates at wirespeed.
This is Cumulus Linux.