I’ve been doing a lot of work recently with VyOS¹, the really amazing open source² Linux based router operating system. A co-worker of mine showed it to me when we needed a capable router in our development environment and we didn’t feel like waiting for finance to approve a Cisco purchase. I have to admit I didn’t quite get it at first. Linux is an OS, not a router! That’s what IOS³ is for! But after digging into it a bit for a budget constrained side project, I’m totally hooked. And I learned, unequivocally, that Linux can function as a very capable router.

One of the oddities about VyOS is the show configuration command doesn’t produce copy/pastable output. This was initially frustrating to me as someone who is accustomed to the way IOS, ASA OS, and NX-OS work: what you type on the command line is exactly what gets put in the running config. And you can copy and paste bits from a saved config to reuse those settings in other devices.

To get similar behavior out of VyOS, run show configuration commands. You can parse this using our friend the pipe character (|) and the match command followed by a pattern⁴ like so:

show configuration commands | match interfaces

I wrote a simple script⁵ to save the running configuration to date stamped file. This could probably get fancier and scp it somewhere, but I just put it on the router itself in my home directory and grab it using an SFTP client.

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#!/bin/vbash
source /opt/vyatta/etc/functions/script-template

run show configuration commands > $HOME/$(date +%Y%m%d-%H%M%S)_$(hostname).txt

Happy routing! And don’t forget to always backup your config!