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Secure Linux Appliances in Your Enterprise

posted Apr 17, 2013, 3:00 PM by John Jones   [ updated Apr 17, 2013, 3:01 PM ]

(Article originally posted at InfoWorld Magazine)

By now you’ve either seen them or read about them. Companies are selling all kinds of useful appliances based on embedded Linux. Some are for small tasks like wireless APs, mobile devices, or cell phones. Others are geared towards enterprise needs like load balancers, routers, and NAS (network attached storage) and SANs (storage attached network). They all run some version of Linux or BSD. You know you have a couple of Linux geeks working for you in the IT department. Why aren’t they coming up with some of these cool Linux appliances for your own company to use? The excellent Debian Router project by Vadim Berkgaut is the help that your Linux admins need to develop their very own Linux appliances.

At my company, q!Bang Solutions, we provide all types of IT solutions, but our strong suit is our solutions built upon Open Source software. Our employees have used the Debian Router Project (which we refer to as “DebRouter”) to build numerous solutions, including firewalls, OSPF and BGP routers, DNS servers, and even VoIP servers. DebRouter is a cornerstone of our technology solutions.

What’s great about DebRouter is that you get a fully functional Debian Linux installation. So you can add whatever software packages you want to extend the functionality of the DebRouter. This is implemented through the usual Debian package management utilities, which means that you can change a DebRouter’s functionality on the fly and in the field after it’s been deployed.

Another important feature of DebRouter is that it boots from a flash device like a compact flash card (via an IDE adapter) or a USB flash drive. So if there are any problems with changes you’ve made, a reboot takes you back to the previous known-good version of your running system. Does this mean that you lose changes you’ve made when power to the DebRouter goes out? No. DebRouter implements a “write to flash” function much like a hardware router or manageable switch. So you can install and configure new packages, test them out, and write your changes to the flash-based boot media if everything went well in testing. If your tests revealed there was a problem, then just reboot without writing the changes to flash and you will roll back to the same state of the filesystem that you had before your changes. This makes it extremely easy to test potentially unstable software and configuration changes. If things don’t work, just reboot, and voila! Your working system is back within seconds.

This also means that the machines are harder for crackers to abuse if they succeed in infiltrating the DebRouter. If you discover that your DebRouter has been compromised, you can reboot and be rid of the cracker. Then you check for security updates from Debian, install them, write your changes, and you’re back up and running. I can tell you from experience that eradicating a cracker’s presence from a normal machine with hard drives whose data persists across reboots is not this easy!

The boot process of the DebRouter provides another nice benefit. DebRouter boots from flash media, creates a RAM disk, copies the flash media’s filesystem to the RAM disk and then unmounts the flash media filesystem and runs from the RAM disk. RAM is fast – lot faster than any hard drive. So now your filesystem I/O speed is absurdly fast. So if you install the Apache web server and put up some HTML and image files, you now have one of the fastest web servers available – without the hassle of a special configuration to load your pages into a ramdisk. It can also run web scripts (such as PHP, Perl, Python, Ruby, etc.) as fast as your normal hard drive based servers do.

What can you build with a DebRouter? Here are a few ideas to get you started:

  • Add the Quagga routing software package to make an OSPF/RIP/BGP router
  • Install the Apache web server with Perl/PHP/Python/etc scripting environments
  • Use the Asterisk software for a cheap VoIP server for a remote office
  • NAT/Firewall
  • Web content filtering via the Squid proxy package
  • Make a captive portal system for wireless networks in cafes or other public access areas
  • DNS server using the venerable and always popular BIND software
  • Create a network sniffer with the tcpdump utility which writes data to a remote NAS or other storage device
  • Combined with a NAS (Network Attached Storage) or an NFS server, a DebRouter can do most anything.

Since most enterprises will try to install all machines in racks, I checked a couple of online vendors to see how much it would cost to build a good 1RU DebRouter machine. I found that a 1RU machine far above the minimum specs can be had for $500, including shipping. This includes a 1RU case, motherboard with all essential functionality on board, a P4 2.8GHz CPU, 1GB ram, and a 512MB CF card and IDE-based CF reader.

So how about a $500 router that can do RIP/OSPF/BGP? Consider both the business and technology reasons that your company might want to use a DebRouter instead of a router from Cisco or one of the other routing big boys. The business side is easy. The hardware is cheap, even for a system with generous amounts of RAM and CPU. For the price of a typical router support contract, you can buy a couple of extra DebRouters to have sitting around as spares ready to jump into action if you have a hardware failure on your primary DebRouter. Subsequent years of support contracts you don’t need to buy equal money that remains in your coffers helping to fatten up your Christmas bonus next year. Of course, let’s not forget that most router vendors charge extra for the advanced software like OSPF or BGP routing, or encryption software so that you can use the more secure SSH instead of the gaping security hole called Telnet to remotely connect to your router. DebRouter has all that (and so much more) for free!

On the technology side, with the screaming fast processors available today, a DebRouter can pretty well hold its own against most of the major router vendors’ offerings. And it’s the versatility of the DebRouter that will likely interest your techies. Did I mention that Linux does 802.1q VLANs? How about an OSPF router that does double duty as a slave DNS server? Or perhaps an edge router that also acts as a VPN concentrator with strong encryption for hundreds of tunnels?

So walk on down to IT and find those two Linux guys tucked away in their cubicles and let them loose on a Debian Router project. They should be glad to have an interesting project to work on instead of trying to recover emails that Marge from Accounting accidentally deleted the other day, and you just might get some nifty devices from them that save you some cash on your bottom line. Your Linux admins are welcome to reach out to me if they need some help or just want to share their ideas on a new use for a Debian Router.

In the future, I’ll touch on embedded Linux in extremely cheap devices that are excellent for smaller tasks.
[My q!Bang Solutions co-owner Josh Kuo beat me to the punch. Read his article "Beef Up Your Wireless Router".]

High Mobley
Co-Owner of q!Bang Solutions