Author: Roo

Ubuntu server 8.04 LTS upgrade to 10.04 LTS

Ubuntu 8.04 LTS desktop edition hit end of life well over a year ago (May 12, 2011), the server version end of life date is April 2013 – not too far away. With a server exposed to the internet, staying up to date with patches is good hygiene – there is also the tried and true “if it ain’t broke, don’t fix it“. While there have only been a few critical patches in the last while, I want to stay on a supported version.

The end of life date is a good motivator, but what actually triggered my upgrade was wanting to make use of encfs – and discovering that the version available on 8.04 didn’t have the feature (–reverse) that I was looking for.  I’m actually only part way there as I intend to upgrade all the way to 12.04 LTS to avoid compatibility issues with data stored with encfs. This post will focus on issues and solutions that I encountered on the way to 10.04.

Initiating the upgrade process is quite easy. If you choose to do this via SSH (as I did) you’ll be warned that this could be a bad idea. In my case console access is possible if I head down to the dusty corner of my basement where it lives, so I felt certain that I could recover if needed.

$ sudo do-release-upgrade

Through the install process you’ll be warned of conflicts with the package maintained version of configuration files and the ones you have. Some of these conflict warnings will be pure console, and others will use the curses library to display it a bit more graphically. As I was doing a fairly major upgrade (8.04 -> 10.04) I opted in many cases to overwrite my configuration file with the package maintained version then perform a manual merge afterwards. If you pick this route make sure to keep good notes on which files need to be revisited AND that you have a full system backup – it is nice that the installation system will copy your old version to .dpkg-old so comparison is easy.

Things seemed to go very smoothly, up until it was time to reboot. Post reboot I could ping the machine but SSH was not accepted. Time to head down and check out the actual console. It turned out that my RAID volumes wouldn’t mount and this derailing the normal start up.

As with many things, someone else had run into pretty much the same problem and posted a solution. Sadly that wasn’t quite the full solution in my case as the RAID5 volume wasn’t being recognized properly. I did find the help I was looking for, so basically here is what I did.

Since my RAID volumes are not needed to boot the OS, I simply skipped mounting those drives. Once logged in I could issue:

$ sudo mdadm --auto-detect
$ sudo mdadm --examine --scan

This gave me:

ARRAY /dev/md3 level=raid5 num-devices=3 UUID=7a6c5b68:6d6d7031:7653325d:7e304e58
ARRAY /dev/md2 level=raid1 num-devices=2 UUID=593e3663:69294b3b:30443245:23496c5f

Which I effectively cut & pasted into the /etc/mdadm/mdadm.conf file with one small change: I replaced /dev/md3 and /dev/md2 with /dev/md/d3 and /dev/md/d2 respectively. I’m not certain this was necessary but it matched closer what the 1st solution I found described and it is working fine in my system.

Once past that roadblock, most of the other things were trivial. I found copying the config files back to my Ubuntu desktop system and using meld to view differences to be much easier than trying to interpret the console diff utility.

There was a warning about the default TCP port changing for postgrey, yet for some reason mine still appears to be running happily on port 60000. I also had some trouble with my ThinkUp installation, one of the required PHP packages (php5-mcrypt) had been auto removed in the upgrade. While I’ve certainly missed something in the process, it’s been a couple of days and I haven’t seen any serious problems due to the upgrade.

How To: Spectroscope from common items

Ok, maybe it’s not very pretty – but it’s a science project you can put together in about 10 minutes once you’ve got the parts together AND those parts are likely things you’ve got around your home now. It was a long weekend and the kids and I were looking for something to make, this fit the bill and just maybe taught them a little bit about science (maybe I learned something too). The original article is a great reference, as usual I’ll repeat the steps here with my notes.

Parts list:

  1. Box – large enough for a CD
  2. CD, used or not
  3. Toilet paper tube
  4. Two razor blades
  5. Tape: scotch tape & silver foil tape (but masking + duct will work too)

For reference, in the picture at the top of the post – the bottom of the box is facing us, and the tube is coming out of the right side.

First we cut an oval hole for the paper tube in the right side. Choose a side, and use the CD as a guide – place it in the lower left corner and mark the center hole. Now use that as a guide to center the paper tube and mark the outside of the tube. Shift the tube left so it’s touching the center of the CD hole marking and mark the outside of the tube. You should have two outlines of the paper tube that you can make into an oval.

The next hole is for the razor blades, it goes on the side to the left of the oval hole. It should be 1/2 inch wide by 2 inches high – give or take a bit. It should the same height up the box as the tube hole (use the CD as a guide) but about 1/2 inch in from the edge. We’re going to cover this slot with the razor blades in a minute.

Now place the razor blades over the second hole and tape them in place. They should fully cover the hole and be spaced as closely together as possible, almost but not quite touching. It is important to have an even spacing top to bottom.

Orient the box as seen in the picture at the top of the post. Place the CD on the side of the box that is lying on the ground now, label side down. Shine a flashlight into the razor blade slit, and hold the tube in the oval at an angle. You may need to close the box to see this, but you should see a rainbow of sorts when you look through the tube at the CD.

Once you’ve got this basically aligned (and don’t sweat it too much), tape things in place. Use the foil tape to seal the box up to prevent any light leaks.

That’s it, we’ve built a spectrometer!

Above is a full spectrum resulting from sunlight. If you look carefully you’ll notice there are clouds as the razor blade slit (diffraction grating) also acts as a pinhole camera.

The pinhole effect is much more obvious in this photo which shows some trees blocking some of the light.

The image on the left is a normal 4′ fluorescent bulb, the one on the right is a T4 fluorescent bulb. The gas signature is pretty much identical.

The image on the left is a CFL bulb, exhibiting the basic fluorescent gas signature. The one on the right is a regular incandescent bulb, notice it is quite similar to sunlight.