Setup DNS, DHCP and Content Filtering using DNSMASQ and HAVP in Ubuntu.

The idea here is to setup DNSMASQ and HAVP to provide DNS, DHCP and content filtering in a Windows 7/Vista/XP client environment on Ubuntu Server Edition. DNSMASQ is a light package which will provide DNS caching and DHCP to a network (amongst other things). HAVP is a proxy server which uses a third party virus scanner (usually ClamAV) to scan internet content for viruses. This assumes that you already have Ubuntu Server Edition installed on a suitable machine and have a working internet connection. In the settings “192.168.1.254” refers to this machine which is acting as a router/firewall, you could equally set it to the ip of another router on the network. “192.168.1.253” refers to the ip of a Windows server. First off install DNSMASQ:-

apt-get install dnsmasq

Edit “/etc/dnsmasq.conf”:-

nano -w /etc/dnsmasq.conf

We now need to set the relevant options:-

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A cost effective alternative to KVM over IP switches

Whether in a co-location centre or at a remote site, looking after a server when you aren’t there in person can be a challenge, particularly if you are conscientious and update your servers regularly – updating a Windows server almost always requires reboot, updating a Linux server will require reboot if the kernel has been updated. What happens if the server doesn’t come up after said reboot? This happens more often than might be expected, so I find it desirable to have a way of accessing the server even if the operating system isn’t available. Traditionally this would be provided by a KVM over IP switch, which redirects Keyboard, Video and Mouse input/output via a web server integrated into a box. KVM over IP switches are expensive (the cheapest one I could find at time of print was €250 and doesn’t work well with mice IMO). However, there is an alternative which is elegant and affordable …

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Boost your mobile broadband, get a HSDPA modem that supports an external antenna.

You are probably at this page because you aren’t getting decent bandwidth and response from your mobile broadband connection. It’s worth noting that even if you use the most expensive ways of boosting the signal you may still receive poor bandwidth and response. This is because there is only so much data that can be carried on the frequencies available, so at times of heavy usage (particularly when there is also heavy phone usage as 3G shares the same radio waves) it doesn’t matter what you do, mobile broadband (or midband as it should really be referred to) will not work well.

Now I have dropped that bombshell I will list the ways of boosting the signal:-

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SIP Communicator the only show in town for VOIP in Linux

I have been trying to reach a holy grail. Well, not a big holy grail and to some people this will seem silly, but I have been longing to be able to use VOIP in Linux and until I discovered SIP Communicator it wasn’t viable.

Ekiga the default VOIP soft phone in Ubuntu just doesn’t cut the mustard. It crashes is difficult to setup and just plain doesn’t work properly for me (I have a mobile broadband connection so jitter is an issue).

As for Twinkle I couldn’t even get it to work. Qutecom was the best soft phone I had used. It crashed a lot on start up, would crash sometimes in calls but at least it was easy to setup and worked up to a point. And then, while trying to help somebody on the Ubuntu forums, the poster, after tearing his hair out trying to find something that just works recommended SIP Communicator. I thought I would give it a try and it was and is a revelation.

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Migrating from Chrome to Chromium

To get a more open source experience I changed from Chrome to Chromium for Linux. It left me without my bookmarks, etc. though. The user data for Chrome is stored in ~/.config/google-chrome. To get my data into Chromium I simple moved the files from there into ~/.config/chromium. Job done.

http://www.google.com/support/forum/p/Chrome/thread?tid=63af2c4e884f0673&hl=en

http://www.ubuntugeek.com/install-chromium-google-chrome-web-browser-in-ubuntu.html

Using a Novatel XUA-1 and X950D in Ubuntu

I read an article recently that suggested using a saucepan as a mobile broadband booster and it peeked my interest enough to give it a try. In case I needed to use my Novatel X950D express card with another machine I had already purchased a Novatel XUA-1 USB to Express Card 36 adapter. This, therefore, gave me a way of placing the modem in the middle of a saucepan, which would be nigh on impossible were the modem in it’s rightful express card slot in the laptop.

Unfortunately, however, due to a production issue at the plant my XUA-1 came wired as “bus powered”, which effectively means it tells the operating system it only has 100ma of power available even though that isn’t true. Subsequently the OS – be it Windows or Linux – won’t then allow the X950D to work in conjunction with the XUA-1.

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Recover a failing Windows hard disk using only free software and your Windows CD.

Scenario.

You have a Windows machine which will not boot up but you can still access the disk, even though it makes various clunking and thunking noises.

Solution.

Install a new hard disk and Partedmagicos on a USB stick or CD and run either “ntfsclone” (the easiest and quickest option) or “dd_rescue”. If the NTFS structure is damaged and you cannot repair it fully using the windows recovery console the latter option is the one you want. Of course you may have Windows installed on a FAT32 partition in which case use dd_rescue.

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Wake On LAN over wireless

What is it?

Wake On LAN is a mature technology for switching on computers over a network or remotely.

Why would I want it?

Perhaps you are a techy such as myself and you want to be able to switch customers computers on and work on them remotely (saves having to tell people to leave machines on if you are working after hours).

I also use it to switch on my Ubuntu machine upstairs when I am downstairs (saves me or my better half having to wait for boot or to get a file to or from the machine without physically going up there).

Is it easy to do?

Yes when you know how ;)

Before I go any further I will mention a caveat. Almost all of the WOL howto’s out there mention using a “magic packet” packet to wake the machine. Unfortunately I found out after much head banging and googling “magic packet” doesn’t work over wireless networks, apparently because wireless frames screw the magic packet up so that the wakee doesn’t recognise it any more.

So if you want to use WOL by sending the wake up through a wireless network your options are limited and it depends on the network card you have. At least 2 of the cards I have support a variety of WOL options “pumbg” and the other one only supports “pg”.

  • P stands for PHY activity
  • U stands for Unicast activity
  • M stands for Multicast activity
  • B stands for Broadcast activity
  • G stands for Magic Packet activity

Firstly I tried phy activity that had the unfortunate effect of starting the machine every few seconds. Then I graduated to broadcast which started the machine periodically (my thick wireless router is sending out broadcasts every hour or so). Eventually I settled on unicast here is how to get it working.

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The importance of a minimal firewall.

I have long been an avid user of the well known interface to iptables – Shorewall. Of late though I have suspected it is slowing my network down. I once decided to see what actual iptables rules it was creating and ran “iptables -L”. There was a lot of output and I wasn’t sure was all of it necessary. It niggled away at the back of my brain for the last few months, and I decided yesterday it was time to do something about it.

I first looked at another “user-friendly” interface that would perhaps give me more control and proper ipv6 support, so I installed Firewall Builder. However it seemed quite complex and after spending some time trying to get to grips with the interface I decided it would be easier to type the rules in manually and anyway that would be the only way I was 100% sure everything in there was needed.

I familiarised myself with the Packet Filtering HOWTO and thought the easiest thing to do would be use “iptables-save” to copy the existing Shorewall rules into an iptables friendly format. The resultant file was 9k long and appeared to have a lot of user defined chains for no good reason. It also didn’t make good use of the multi-port option for tcp connections and therefore there were dozens of rules where there only needed to be one.

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