Self-proclaimed genius, and ruler of the Internet. System admin the rest of the time

I’ve been playing with cobbler (through Spacewalk) for some time now.

One thing I had been meaning to do for some time was to “integrate” cobbler into the current PXE boot setup I have using gPXE.

Today I finally got around to doing it. It’s actually very easy, but I thought that there may be others interested in doing this so I figured I’d create this post.

I prefer to use HTTP rather than TFTP for PXE booting for various reasons, so I use so the way I got this working was by adding the following to my Spacewalk server’s Apache configuration:

Alias /pxe/ "/var/lib/tftpboot/"

<Directory "/var/lib/tftpboot/">
  Order allow,deny
  Allow from all
</Directory>

This is quite self explanatory, it just creates an alias from /pxe/ to the directory cobbler creates the configuration files for pxelinux.
Next, I created a new entry in my current PXE boot menu:

label spacewalk
  menu label Spacewalk
  kernel http://boot.internal.hamzahkhan.com/gpxe/spacewalk.gpxe

This will make gPXE grab http://boot.internal.hamzahkhan.com/gpxe/spacewalk.gpxe, and “do” what ever is inside that script when it is selected in the menu.
Next we create spacewalk.gpxe:

#!gpxe
set 210:string http://spacewalk.internal.hamzahkhan.com/pxe/
chain http://spacewalk.internal.hamzahkhan.com/pxe/pxelinux.0

DHCP option 210 is used to define the prefix path for pxelinux to search for its configuration files.
And thats all there is to it really!
Now when when the Spacewalk option is selected from the menu, pxelinux will start up, grab it’s configuration files over HTTP (rather than TFTP) and in my case, display the cobbler boot menu!

For the last two days I have been playing games on my PS3 on-line, something I haven’t done for the last 3 years that I have had it.

To get better performance I decided to look at the commonly used ports, and the ports which PSN uses so I could forward them to the PS3. Before digging in myself, I decided to do some Googling and the answers I found frustrated me quite a bit.

There are multiple websites stating that port 80 and port 443 need to be forwarded to the PS3!

That is completely incorrect!

The PS3 only needs to be allowed to send outgoing packets to servers listening on 80 and 443, it does NOT its self listen on port 80 or 443.

There isn’t any real harm in forwarding those ports to your PS3, but there isn’t any benefit either!
I think this common misconception came into existence because often in manuals it lists port 80 and 443 as a port that the game or device uses…. but does not state that it only needs to be able to connect to external servers running on port 80/443 (In this case, the PSN servers!).

I also notice that a lot of sites recommend forwarding TCP port 5223, but running a packet sniffer will show you that this is not needed either!

If you run a packet sniffer yourself, you will notice that it is not the PS3 that is listening on this port, but rather Sony’s servers (which all seem to have the reverse DNS entry of service.playstation.net!). The PS3 (naturally) uses a random, high numbered source port, and sends the packet to Sony’s servers listening on 5223.

If you don’t believe me, fire up a game, and use a port scanner to scan ports 80, 443, and 5223 on your PS3s IP address. I assure you they will all be closed. Now, scan one of Sony’s servers (Sorry Sony! Please don’t sue me… its just a port scan! ):

# nmap -p 5223,443,80 198.107.130.128

Starting Nmap 4.11 ( http://www.insecure.org/nmap/ ) at 2011-01-26 00:28 GMT
Interesting ports on 198.107.130.128:
PORT STATE SERVICE
80/tcp closed http
443/tcp open https
5223/tcp open unknown

Nmap finished: 1 IP address (1 host up) scanned in 1.108 seconds

As you can see, this in-particular server is listening on 443 and 5223!

I have also seen a bunch of other ports which people claim need to be forwarded, but probably do not, but I won’t comment on those yet as I have yet to confirm them.

Hopefully Sony will wake up, and start deploying IPv6 and also release a firmware update with IPv6 support so we no longer have to use NAT, but for now I’m considering making a little page which will contain port numbers and protocols, which have been confirmed by me, that need to be forwarded to the PS3 for optimal performance.

For quite some time I’ve been using GnuCash to keep track of my bank account income and expenses and I find it very very useful, but lately I have felt the need for a few features that are currently not in GnuCash.

One of these features is the ability to “link” books. For example, It would be nice if I could have a separate “book” and set of accounts from my family which only I can see, yet still be able to transfer directly into their GnuCash accounts, and maybe also the ability to have a “household” where everyone can can create transactions into but not let everyone else see their personal books.

Maybe it is a silly idea, but I think it would be quite useful (at least for me anyway), and it would really help visualize the flow of money inside the household.

Another feature I’d like in GnuCash isn’t really a “feature”, but it would be nice to see a mobile client for it. I don’t really want a web interface based client, although that shouldn’t be hard considering GnuCash supports using a SQL database to store your accounts, but rather a “real” client for Android or iOS.

Now that I have bought a HTC Desire Z (which I love so far!), I have been looking into Android development, so maybe creating an Android client could be my first, small “proper” programming project.

Like most geeks like me, my interest in technology is a personal one.

From a very young age, I was very interested in how computers and other devices worked to the point where I often tried to find out, and in the process breaking a lot of things.

My first “personal” (it was actually shared with my siblings!) computer was an Apple Macintosh Performa 5200 (Oh the horror!). It was running Mac OS 7.something (I still have the original installation CD somewhere! ). While using this machine, I messed around a lot with Virtual PC and Open Transport, although I didn’t really know what I was doing at the time!

My first real exposure to networks was when I got a broadband connection, and needed to “share” it between my fathers machine, and the machine I shared with my siblings. I originally done this through Windows 98 on my fathers machine using a free application (I seem to have forgotten the name!) which provided firewalling and NAT functionality.

Just before the time I got my broadband connection, and was using a dial-up connection on the Mac I was also quite interested in web development. I created a lot of very badly made websites and hosted them on the many free web hosts that were available. Most of these free hosts put A LOT of adverts on the pages, and only gave a few megabytes for data!

This was a huge problem since I wanted to put a lot of images, and other files (Gameboy/SNES ROMs! ) onto the site. So through a series of events after getting a broadband connection, I discovered I was able to host a web and FTP server on my own computer!

Eventually after getting sick of using Windows for sharing my network connection and having to wipe my machine after every few weeks due to IIS worms, I discovered that Linux would do a much better job for both purposes. Since then from then on I’ve been pretty much hooked to the wonderful world of Linux, networks and other geekery!

Well, my desk current has the following on it:

• Two Samsung 2043BW monitors
• A Cisco 7912 IP Phone
• A HORRIBLE 8 Port Cisco 1548 Microswitch
• A 500GB Seagate FreeAgent USB drive
• My Sony Viao laptop
• My Desktop Keyboard (A crappy Microsoft one).
• My Logitech MX Revolution wireless mouse
• A VERY large Razer Goliathus mouse pad
• A desk lamp I got from IKEA
• A pencil pot which has a bunch of pens, pencils screws, a CompactFlash card, and other various small USB attachments (Flash drive, Bluetooth dongle etc)
• And some books and bits of paper

I find it very difficult to concentrate when there is a lot of clutter on my desk, so before doing any real “hacking”, I clear any clutter.

My favorite time to hack would be during a warm night in summer with my desk lamp switched on.

But when it is cold, I prefer to hack during the day with as much light coming into the room as possible and with the room temperature at least 25 deg C.