Local and Remote Kernel Upgrades – Failsafe Grub

February 28th, 2009

Grub (and LILO too for that matter) has a useful ‘failsafe’ feature that can be configured. This proves especially useful for remote kernel upgrades, where a failed boot will render your machine offline and unavailable.

Here is my standard grub config. I have just added my new 2.6.28 kernel.
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Linux and the Huawei HSDPA 3G E220 modem for mobile broadband

February 28th, 2009

Installing the Huawei E220 modem under Linux is so so easy. Probably easier than running through the Windows XP Setup tool actually!

Prerequisites:

1. Kernel version equal to or greater than 2.6.20 (There are workarounds availble for older kernels)
2. wvdial (You can use any serial dialer I guess)
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Linux PPTP (Poptop) VPN Setup with MPPE and MPPC

February 15th, 2009

Here’s a quick guide that I write as I’m setting up PPTP/MPPE/MPPC on a Linux server. My preferred VPN technology is OpenVPN mainly because it’s so quick and easy to set up and use, however in some cases PPTP is required chiefly when the Client wants to use the inbuilt Windows VPN capabilities rather than having to deploy 3rd party software.

My server is a Debian (of course) etch machine, with 2.6.24 (from source) kernel. My client is Windows XP Pro SP3.
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Linux Squid Transparent Proxy

February 9th, 2009

There are a number of reasons why you might want to use Squid in transparent mode, I won’t go into them – I’ll just explain how!

In Squid versions before 2.6, you’ll want to edit your configuration to specify:

httpd_accel_host virtual
httpd_accel_port 80
httpd_accel_with_proxy on
httpd_accel_uses_host_header on

In 2.6 versions and beyond, you can append ‘transparent’ to the end of your http_port option, i.e.:

http_port 192.168.1.1:3128 transparent

Squid will now be ready for transparent proxying. Now create some iptables rules to push all outbound port 80 traffic through squid:

iptables -t nat -A PREROUTING -i eth0 -p tcp –dport 80 -j REDIRECT –to-port 3128

eth0 is the local side of your router, –dport 80 specifies a destination port of 80 (HTTP) and we’re going to redirect it to 3128 where your Squid proxy runs.