Fixing Windows XP MBR without the install CD

I just had a mishap with a failed Ubuntu install (GRUB failing due to the BIOS having problems with large drives) on a laptop and needed to boot back into XP. "Normally" (or rather, in the past) the XP install CD would do the trick, but because the laptop has a SATA drive the install CD couldn't find any disks.

I could possibly have made a custom install CD (the laptop doesn't have a floppy drive for the SATA drivers the install CD needs) but an easier solution was the great SystemRescueCD. This is completely free and works well.

I booted the included FreeDOS image, typed fdisk at the FreeDOS prompt, selected my XP partition, and hey presto, a rebuild MBR option!

So there you have it, free MBR repair without the dodgy XP install CD. As I didn't find this by Googling for a solution I'm posting it here hoping it will help others in the same pinch.

Commodore 64 palette file for GIMP

I wasn't able to find a good C64 palette file for GIMP, so I used the values from Philip 'Pepto' Timmermann's brilliant webpage about the C64 colour palette and typed the values into this .gpl file, just in case anyone should have use for it.

Automatic directory spesific saving of torrent-files in Firefox

There is (as far as I know anyway) no easy way to specify which directory to save files in by file types in Firefox. There are addons, but the only good one I found required you to open the Open-or-Save-as requester. Therefore, I made this little shell-script:

#!/bin/bash
mv $1 ~/torrents/
rename 's/\[.*?\]//g' ~/torrents/$1
exit

Save this script and do a chmod u+x on it, then point Firefox to use it on torrent files. (Edit/Preferences/Applications) Obviously, change the directory to where you want your torrent files. Of course this can be used for other file types as well.

The script also strips out those annoying square bracketed site ads like [ISOHunt] etc. (Square brackets seemed to confuse rtorrent here.)

IPv6 with 6to4 tunneling in Debian made easy

I tried to find an easy way to implement IPv6 via 6to4 on my Debian server, but everything I found required some sort of manual intervention in the case of reboots/new IP addresses from my ISP, etc.

So I made this little init.d script using snippets from all around:

#!/bin/sh
# $Id: tun6to4 init.d script v0.1

#Change "eth1" in the following line to your own public interface:
IPV4=$(ifconfig -a | awk '/eth1/{p=1}p&&/inet addr/{sub(".*:", "", $2);print $2;exit}')

STFADDRESS=$(printf "2002:%02x%02x:%02x%02x::1" `echo $IPV4 | tr "." " "`)

case "$1" in
start)
echo -n "Starting 6to4 tunnel: "
/sbin/ip tunnel add tun6to4 mode sit ttl 64 remote any local $IPV4
/sbin/ip link set dev tun6to4 up
/sbin/ip -6 addr add $STFADDRESS/16 dev tun6to4
/sbin/ip -6 route add 2000::/3 via ::192.88.99.1 dev tun6to4 metric 1
#The following line enables forwarding from eth0
# /sbin/ip -6 addr add dev eth0 $STFADDRESS/64
echo "."
;;
stop)
echo -n "Stopping 6to4 tunnel: "
/sbin/ip -6 route flush dev tun6to4
/sbin/ip link set dev tun6to4 down
/sbin/ip tunnel del tun6to4
echo "."
;;
restart | force-reload)
$0 stop
sleep 2
$0 start
;;
*)
echo "Usage: /etc/init.d/tun6to4 {start|stop|restart|force-reload}"
exit 1
esac
exit 0

Modify the first uncommented line with your own lan interface, save the file as /etc/init.d/tun6to4 , then do a:
$ update-rc.d tun6to4 defaults
And you should have IPv6 connectivity up and running automatically. On reboots, the script should find your DHCP assigned IP-address and use it accordingly.

If you want to forward from your LAN, uncomment the commented /sbin/ip line and change eth0 to your LAN interface.

If you get a new IP address you'll have to rerun the script. Oh, and the ipv4-extractor uses awk.

Please note, I am not a Linux expert. If you have improvements, please share them!

Blocking a user group from your internal network in Linux

I recently found out that IPtables features owner matching for TCP packets. This means you can block out packets from certain groups from accessing your local network.

In my scenario, I have a Debian server beeing a physical gateway between my local network and the outside world. Now, some of my friends also has shell accounts on this box. And while I do trust them, it's nice to know they can't access all my stuff (like open smb shares) on the local network.

So how is this done? It's dead simple when you know how. Add the following iptables rule:

iptables -A OUTPUT -m owner --gid-owner 2000 -d 192.168.0.0/24 -j REJECT

This will block gid 2000 from accessing the 192.168.0.* network. Obviously, change this for your own needs. Then add a group called guests or something with a matchind gid, I just added the following to /etc/group:

guests:x:2000:

And ofcourse link the guest users to the guest groups. You can edit /etc/group by hand or use the following command for each of the users:

usermod -g 2000 guestusername


Google with SyncML support, now supports Symbian

I just saw this on the N82 Blog, (thanks, Mike!) Google has implemented SyncML support, so you can now synchronize your Google contacts with those on your phone. A nice bonus is having a backup of your phone contacts.

Unfortunatly, calendar synchronization is not supported yet. For that, use GooSync.