I’ve had a few nasty experiences this week with Linux and figured I’d vent here. Unlike my previous efforts with Linux From Scratch and Gentoo, my complaints this time around are related to upgrading Ubuntu.
Ubuntu 10.04 to 12.04: Save yourself the trouble
At this point the current Ubuntu LTS release (12.04) is my preferred distribution to work with: it has become widespread enough that troubleshooting and previous solutions online are easy to locate. In a professional capacity, I also maintain systems that are still on 8.04 LTS (supported until April 2013, so we have to be pretty aggressive about replacing them) or 10.04 LTS (good until April 2015).
I attempted to complete two upgrades from the 10.04 release this week to 12.04 – one 10.04 LTS “desktop” installation, and one 10.04 LTS headless server installation. Both were virtual machines running under VMWare ESXi, but neither had given me any trouble during normal use.
Canonical’s updater process (the wrapper around dist-upgrade) appears to be pretty slick; it gives you appropriate warnings, attempts to start a SSH daemon as a fallback mechanism and starts on its merry way to download the necessary packages to bring your system completely up to date. On my 10.04 desktop VM, the installer fell apart completely during the package replacement/removal/installation sequence. I was left with two nasty message boxes: one advising that my system was now in a broken state, and another that completely contained rectangular, unprintable characters.
To put it bluntly, I was not amused, but it wasn’t a critical system and I was content to replace it with a fresh 12.04 installation rather than waste additional time troubleshooting with apt or dpkg. Strike one for the upgrader.
At least the server came back up!
Next on the upgrade schedule was the 12.04 server VM. Install, package replacement and reboot went fine, but I had several custom PPAs installed to support development of XenonMKV (Github page) – specifically ppa:krull/deadsnakes to add Python 2.7 to Ubuntu 10.04.
For some reason, though, I’d gotten it into my head this evening to check out Mezzanine as a potential WordPress replacement. Mezzanine uses Django, a Python Web framework, and the list of supported features is pretty encompassing.
Sidebar: Django and mod_wsgi – complicated enough?
One of the most irritating things from a system administration point of view is getting Web applications to run in a standard server environment – typically a Linux base system and Apache or nginx to serve content. I suppose I’ve been spoiled with how easy it is to get PHP-based sites up and running these days in that configuration by adding an Apache module through apt. A lot of new Web app frameworks come with their own small webservers for development and testing, but generally their creators recommend that when you’re ready to put your site live, that the product run under a well-known Web or application server.
The Django folks recommend using mod_wsgi in their documentation, which in and of itself really just says “RTFM for mod_wsgi and then you’ll have a much better idea of how to do this.” I had to go poking around on Google for the installation article since there are some broken links, but okay, it’s an Apache module with a small bit of configuration (even though a simple walkthrough in the Django documentation would go a long way to making deployment easier.) This is where I ran into my dependency/PPA problem on Ubuntu 10.04.
I’ve suppose I’ve screwed the pooch…
Running the suggested command, I tried: sudo apt-get install libapache2-mod-wsgi and got the following
The following packages have unmet dependencies:
libapache2-mod-wsgi : Depends: libpython2.7 (>= 2.7) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
Backtracking, I then found out why the library wasn’t going to get installed:
The following packages have unmet dependencies:
libpython2.7 : Depends: python2.7 (= 2.7.3-0ubuntu3.1) but 2.7.3-2+lucid1 is to be installed
Aha! The Python installation from the PPA for Lucid – 10.04 – was installed and acting as the 2.7 package. Since the newly-upgraded Ubuntu 12.04 uses Python 2.7 as a dependency for a good portion of the default applications, I couldn’t just purge or uninstall it, and my attempts to force a reinstallation all ended in:
Reinstallation of python2.7 is not possible, since it cannot be downloaded.
At this point it looks like I’ll have to rebuild the server VM as well, but if any readers have any bright ideas on fixing this dependency hell – please comment with your suggestions!
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