Recently in solutions Category

This time from the department of almost wasted time...

We all know that serial ports come very handy when you need to (re)configure something like a switch/server/firewall or similar device. In theory you can do that over TCP/IP nowadays with one hint - you need to have connectivity. All would be ok if not the fact that those very switches/firewalls you want to reconfigure actually provide the connectivity you need :-)

The Idea

Now... why spend hundreds of pounds/dollars on off-the shelf kit? Sure, it's cool, properly built and works unless you mess it up, but where's the fun part?! Today I needed a very very quick and cheap solution, so:

1. SheevaPlug - £114.00
2. 13-port USB hub - £19.99
   
3. USB-serial dongles (pl2303) - £14.99 each

This way I have fully networked console server with 4 ports just under £200 - acceptable, especially when the whole thing is running off DHCP and calls home via OpenVPN - very easy to deploy!

Tricky bits

Generic Sheeva has one USB host port and hub has 13 of them - I want to send it off to remote location and have somebody plug it in and not mess up what's where. Trick is to write appropriate udev rules to detect adapters and give them ttyUSBn names according to physical port on the hub.

All would be fine and easy if it worked as documented - sadly it doesn't. First problem was that ATTRS{devpath} (as returned by udevadm info --attribute-walk -n /dev/ttyUSBn that allows to distinguish usb ports) was used by rule in tests but wasn't propagated properly on none of my Debian or Ubuntu boxes. Then I tried to match KERNELS for parent devices - nope... if you go too far up the tree it doesn't see s**t :-/

Recently I had some serious problems with wi-fi at home - especially one of the laptops was dropping off and couldn't come back. Quick survey using Kismet and other tools to scan what's flying around has proven that my network is in less populated part of the spectrum (at least here) but still, problems are getting worse and worse.

I was fully aware of Wi-Spy by Metageek, seen it in action previously but never had a chance to buy one. Part of the decision was the price back then, maybe now it would be another game, but anyway - I got myself another device, made by well known wi-fi vendor Ubiquiti and it's called AirView2.



What's so special about this one? Why it's better than Wi-Spy?

First of all I didn't say it's better. It's different, woks with Linux, Mac OS X and Windows, has a nice price tag and does pretty much the same as Wi-Spy. Let's have a closer look then, shall we?

It seems that the weather forecast for the Internet is a bit "cloudy" nowadays and it will stay this way at least for some time. The "clouds" are a very hot topic right now and more and more companies try to get on the bandwagon as soon as possible - some just run tests while others go into production. You can run "your own" cloud environment for peanuts, the costs are so marginal that it made me laugh when I got my last bill from Amazon AWS, but nevertheless it doesn't always calculate to run your stuff on commercial cloud, especially if you have hardware at hand. The DIY approach is easier than it seems to be. Here is how I've built my own, small "cloud" to solve a problem I was facing at work. It's not a rocket science, it's not full blown management system with hundreds of machines... it works for me and I believe anyone can build similar system - hopefully much better than I did with mine.

Staying away from terminology like HPC/cluster/cloud/grid and meanings of those I use the term "cloud" because I think it's the closest to what I've got now in my prototype - it's still work in progress and it gets even more "cloudy" or change shape otherwise. There won't be any code this time - maybe when I finish it properly and have some proper performance stats - so far it's just a running and usable PoC I describe here :-)

As a follow up to my previous post I've run my Nagios installation on Soekris net4801 implementing the advice I've given you in my last post (focusing on slow I/O when writing to CF Card), describing the platform and what can be done with it. The changes in system behavior are huge - in a positive way of course.

First of all the system is not so overloaded now and I guess I could double the amount of tests run on this platform without getting into trouble like before. At the moment this system is monitoring 36 machines with 86 services in total. Some time ago I had to stop adding and literally remove some less important tests, because most of the time I was getting false positives - usually warnings, with comment that the plugin has timed out. So how big is the difference?

This article is a translation of my other post published in Polish - Ratowanie danych z NTFS ze zniszczonym MBR i MFT.