Backups of Backups

My backup strategy for my machines at home can be effectively described as “scatty, but thorough“.  Or at least until I actually have a major crash and need to recover that important file that was outside of my normal documents, code repositories, and archived folders.

I am one of those sorts of people that has backups everywhere.  Folders stacked away with old dusty (and probably now useless) dvds.  Old hard drives filled with duplicates and archived files, stacked up in the back of cupboards and flung next to jam jars.  SD cards, USB keys, backups to other drives, backups to the machines on the other side of my flat, backups off-site.  Backups of backups backed up during the last backup.

So I decided to add one more with an external hard drive that I could plug in every now and then.  But backups aren’t really the point of this post.

Linux has a really powerful device manager called udev which detects when things are plugged into your machine (including hard drives), which you can write rules against, and have commands automagically executed.  This is really cool for my new hard drive, which can now automatically start backing up without regular cron jobs checking to see if it’s plugged in or not.  This is not the same as autorun files, it relies on that hard drive being plugged into that machine.  So don’t start crying about all the security risks with autorun, please.

Here’s how you do it.

Code block

udevadm info -a -p  $(udevadm info -q path -n /dev/sdc)

You’ll get a whole bunch of output from that, including (among a lot of other output) a line that might look a little like this:

Code block

ATTR{serial}=="312581808"

There are a lot more you can use as well, but this will identify your device.

Now create a new file inside /etc/udev/rules.d/, such as /etc/udev/rules.d/81-usb-drive.rules

Code block

KERNEL=="sd?1", ATTRS{serial}=="312581808", SYMLINK+="backup-drive", RUN+="/bin/sh /home/user/scripts/backup-to-drive.sh"

Now every time you plug in that drive, that command is going to be executed (so include for example, the script that is going to run your backups).  Cool, eh?

I started thinking about other applications; syncing podcasts, ebooks and music are the obvious choices. Even as a crude simple method of executing commands on a box you don’t even usually login to.  Or you could use this technique to build yourself some poor man usb-based security.  Keep decryption keys on your thumb drive, and have it auto decrypt volumes on your machine when you plug in that particular drive.

Just don’t forget to keep a backup of the thumb drive, yeah?

• Eee PC 701
• Nokia N95
• Bluetooth dongle
• Ubuntu Eee installed on the 701 (not Xandros – although check out these scripts if you don’t want to change)
• T-Mobile UK contract with included data plan (preferably).  And Internet already working on the phone.

You’re going to be setting up your connection though pppd, and all of these instructions are based on instructions that I’m going to steal, slightly change and probably skip parts to suit my purposes (and hopefully yours) perfectly.

If your set-up doesn’t match exactly, perhaps you can make use of both pages and work out where things should change.  Or lovingly rip these instructions off, as I did – to make your own.

Setup your bluetooth dongle
First off, you’re going to need an apt repository that has the bluez-utils packages in. So open up a terminal
sudo nano /etc/apt/sources.list
and add the line
deb http://ftp.de.debian.org/debian etch main

Then you can install the package.

apt-update
apt-get install bluez-utils
/etc/init.d/bluetooth restart
lsusb | grep -i bluetooth
(should show the bluetooth device)
hcitool dev
(also lists bluetooth devices)


Setup networking

You can grab my gprs-settings which should be put into /etc/ppp/peers directory, and untarred.
tar -xvf gprs-settings.tar

Pair the phone

First, get the bluetooth ID of the N95
hcitool scan
Then pair your Eee with your phone, you have to do this from the N95.
Bluetooth -> right arrow (Paired devices) - Options
New paired devices (search)
Choose your eee and then type the pairing keys (anything of your choosing

Bind bluetooth to an rfcomm device

We use “rfcomm” to bind the bluetooth connection to a device. So first, find out the channel the phones bluetooth dial up networking system is on. You can do this with sdptool (Service Discovery Protocol tool):
sdptool search dun
Service Name: Dial-Up Networking
Service RecHandle: 0x1001e
Service Class ID List:
"Dialup Networking" (0x1103)
Protocol Descriptor List:
"L2CAP" (0x0100)
"RFCOMM" (0x0003)
Channel: 2
Language Base Attr List:
code_ISO639: 0x454e
encoding: 0x6a
base_offset: 0x100
Profile Descriptor List:
"Dialup Networking" (0x1103)
Version: 0x0100

Note the “Channel: 2″ which show which channel to bind.

Then to bind the channel (in this case #2) to one of the rfcomm devices (for example, rfcomm0):
rfcomm bind 0 11:22:BE:EF:44:33 2
You can see the binding with:
rfcomm
rfcomm0: 11:22:BE:EF:44:33 channel 2 clean
You might find you need to reset the bind and restart it every now and then (especially failed connection attempts)
rfcomm release 0
rfcomm bind 0 11:22:BE:EF:44:33 2
You can edit the settings in “/etc/bluetooth/rfcomm.conf,” set bind to “yes” and give the device and channel for rfcomm0. Then you can put these commands into /etc/init.d/bluetooth and it will automatically bind and release the rfcomm device:
# At the end of the "start)" section
rfcomm bind all
# At the beginning of the "stop)" section
rfcomm release all
Start pppd to connect.
Start up pppd.  Command line first, but because we’ve called it ppp0, you will later be able to do this via the normal ubuntu eee networking menu in the menu bar.
% pppd call ppp0
You should now have a ppp0 interface in your ‘ifconfig’ output that is up and running. The output should look something like this:
# pppd call ppp0
Press CTRL-C to close the connection at any stage!
defining PDP context...
rAT
OK
ATH
OK
ATE1
OK
AT+CGDCONT=1,"IP","general.t-mobile.uk","",0,0
OK
waiting for connect...
ATD*99#
CONNECT
Connected.
If the following ppp negotiations fail,
try restarting the phone.
Serial connection established.
using channel 1
Using interface ppp0
Connect: ppp0 <--> /dev/rfcomm0

You can hit control-c on the pppd process and it will shut down the connection, then you can release the rfcomm binding.

So… as I was saying… It’s not the easiest thing in the world to get going, but once you’ve got the hang of it, and set it up once you’ll have a connection everywhere you go.

Eee PC compared to a John Grisham paperback, and full size laptop

I recently bought myself an Asus Eee 701 4G Surf from Expansys for the bargain price of 169.33 including delivery.  If you don’t know about these tiny laptops, they’re low-spec, cheap machines often times running a Debian-based Linux installation called Xandros, rather than Windows (although XP versions are also available in the higher spec versions).  Its key specs are a 7-inch screen, 512MB of RAM (upgradeable to 2GB), built-in WiFi and hard wired ethernet ports, 4GB solid-state drive, weighing only 922g, and really really small.

For those of you that just about nodded off to sleep – it’s really light, really small (for a feature-packed laptop, I mean), and lets you use word processing, spreadsheets, browse the Internet, read emails, blogging, instant messenger, Skype and, well – just about everything you’d normally do on your laptop really.  Except… did I mention it’s really portable?

I’m not totally sure where it fits into my technology arsenal yet.  It’s certainly not a desktop replacement, and it might even be best described as a second-laptop (the first of which, I hasten to add, spends way more time charging than it ever does getting used).  But the Eee PC is certainly a lot easier to carry around, and more likely to be dropped into my rucksuck as an afterthought since it takes up so little space.

It’s also been described as “something to play with” and the Eee fits into this category just as well as it would as a solid dependable netbook (if you’d rather leave the endless tinkering alone).  Perhaps it’s because the device is so cheap, or easy to reinstall the base system with all your essential apps in tact (take that Microsoft) – but even if you’re just looking for an alternative to Windows, the Eee might just be a good place to start.

So, expect more posts about the Eee shortly – the usual technical-guides are going to help me rebuild the system if I do manage to break it – as well as give me an excuse for something to write about

No it’s not.

It’s a micro-blogging tool which performs about the same function as your Facebook status, with a bit more history and more conversation potential than real speaking. It also falls into the category of “shiny web things” that the magpie’s of the Internet world run bounding towards with wings flapping, declaring their undying allegiance and overwhelming excitement about the grand new era of technology, society and communication.

I am said magpie. I just haven’t had much use for it, so whilst most people are bounding towards Pownce with their wings wide open, I’m still trying to find an excuse.

My Twitter feed is decidedly empty, having originally opened it as a way only of updating my Facebook status before I realised that was syndication for the sake of it (See integrations with BrightKite, Loopt, and Flickr integration for reference). But I do get a kick out of things like the Tower Bridge Tweets. The wonderful thing about this Web 2.0 stuff is that you don’t have to use any of it for what it was intended for (which is usually so vague and fluffy, it only really starts to take shape after the rules have been broken).

So I grabbed a copy of the Net::Twitter module for Perl and before you know it, my script that monitors if the Wifi connection on the Blakepics server had gone down was happily tweeting away with only three more lines of (my) code.

use Net::Twitter;
my $twit = Net::Twitter->new(username=>"username", password=>"password", source => "DowntimeMonitor" );
$twit->update("Internet connection ".($state ? "is now up" : "has been restarted"));

Most of the solutions I came up with involved things like ‘spending money’, which I’m slightly adverse to do if I can do it with the existing kit, so these are the really basic steps to turn the existing linux box (with both wireless and wired cards) into a useful bridge. As usual, don’t be fooled into thinking this guide is here for anyone else, as much as it’s here for me when I need to rebuild the machine and I’ve forgotten it all. But feel free to leave a comment about how much warmer and fuzzier I’ve made your life through your use of these “instructions”.

The current configuration

Fedora 8 installation
Wireless Ethernet (ath0) card is connected as 192.168.0.8
Wired Ethernet (eth1) card is connected as 192.168.1.8
Named/bind/DNS server already configured and set-up to accept requests on 192.168.1.8
The Xbox will be wired, on 192.168.1.20

Setting up Fedora

Setup the forwarding rules

#Outgoing requests
iptables -t nat -A POSTROUTING -s 192.168.1.8/24 -o ath0 -j MASQUERADE
iptables -A FORWARD -s 192.168.1.0/24 -o ath0 -j ACCEPT
iptables -A FORWARD -d 192.168.1.0/24 -m state --state ESTABLISHED,RELATED -i eth1 -j ACCEPT
#Incoming requests (port forwarding)
iptables -t nat -A PREROUTING -p tcp -i ath0 -d 192.168.0.8 --dport 88 -j DNAT --to 192.168.1.20:88
iptables -t nat -A PREROUTING -p tcp -i ath0 -d 192.168.0.8 --dport 3074 -j DNAT --to 192.168.1.20:3074

Save your rules so they’re applied on start-up
sudo iptables-save > /etc/sysconfig/iptables

Enable ipv4 port forwarding
nano /etc/sysctl.conf
Change this line
net.ipv4.ip_forward = 0
to
net.ipv4.ip_forward = 1

The client machine / Xbox 360

Now on your client machine (note this will only have a wired connection).
IP Address: 192.168.1.20
Subnet mask: 255.255.255.0
Default Gateway: 192.168.1.8
DNS Server: 192.168.1.8

You’re going to need a DHCP server so that these settings are automatically assigned to the XBox 360. If don’t have one for your subnet already, you can set it up through dhcpd. You’ll probably want to do something about

Edit /etc/dhcpd.conf

ddns-update-style interim;
# HardWired
subnet 192.168.1.0 netmask 255.255.255.0 {
option routers 192.168.1.8;
option domain-name-servers 192.168.1.8;
authoritative;
range 192.168.1.10 192.168.1.20;
}
# Assign a static IP
host xbox {
hardware ethernet 00:45:40:10:FE:12;
fixed-address 192.168.1.20;
}

Then restart dhcpd
/etc/rc.d/init.d/dhcpd restart

Router

Remember those ports we forwarded on the server? You’ll also need to add port forwarding to your router, to forward the same ports (88, 3074) to the Fedora machine on 192.168.0.8.

And that’s really it. You should now be able to connect to the Internet without any troubles.

1. System won’t boot. GRUB complains of Error 15: File not found when attempting to load kernel.
   • Something bizarre happened to the IDE / SATA ordering in this release? Boot the system from the DVD again, and select ‘rescue an install system’.
   • Open up ‘nano /boot/grub/grub.conf’
   • Change this line, ‘root (hd1,0)’ to root ‘(hd0,0)’
2. Wireless card won’t start.
   • Plug in Ethernet cable.
   • Make sure livna repository is enabled.
   • Upgrade the kernel to the latest: ‘yum -y upgrade kernel’
   • Reboot into new kernel.
   • Install madwifi drivers. Why does this have to be done for EVERY upgrade? ‘yum install madwifi’
   • Restart the network ‘/etc/rc.d/init.d/network restart’
3. Cyrus imapd won’t start. Complaining of libdb-4.5 library missing.
   • Upgrade Cyrus, and make sure it installs the db4-utils package, this time. ‘yum upgrade -y cyrus’

One of these days I’ll move to a real Linux distribution, rather than the current hobbyist affair provided by Fedora. One of these days.

Well it has to change. Right now.. So this evening is all about the introduction to my Myth TV posts, which will serve as some sort of inadequate guide to getting an open-source media center up and running with digital tv recording, playback, tv guides as well as all the networkable, internet-ready, upgradeable, linux hardware hell you’d expect from such a project. Much more fun than going down the shop and buying a complete system. You can’t imagine.

Wait. Shit.

Okay, there will be code. There will certainly be text-only configuration files. Hopefully, I can get a llama in there somewhere… Hopefully.

So first off, create the certificates for your Cyrus IMAP server (you’ve already set all that up, right?)

openssl req -new -nodes -out req.pem -keyout key.pem
openssl rsa -in key.pem -out new.key.pem
openssl x509 -in req.pem -out ca-cert -req \
-signkey new.key.pem -days 999
mkdir /var/imap
cp new.key.pem /var/imap/server.pem
rm new.key.pem
cat ca-cert >> /var/imap/server.pem
chown cyrus:mail /var/imap/server.pem
chmod 600 /var/imap/server.pem # Your key should be protected
echo tls_ca_file: /var/imap/server.pem >> /etc/imapd.conf
echo tls_cert_file: /var/imap/server.pem >> /etc/imapd.conf
echo tls_key_file: /var/imap/server.pem >> /etc/imapd.conf


Then generate the certificate for the client.

openssl pkcs12 -export -in server.pem -inkey server.pem -out iestuff.p12

You’ll need to add that iestuff to your trusted certificates – but that’s pretty much it No more annoying messages from Outlook.