First, I should mention that Canonical numbers Ubuntu's releases not in sequential order, but after the year.month in which the release went public. So, version 11.04 dates to April 2011, 11.10 dates to October 2011, and 12.04 dates to April 2012. Canonical tries to put out a release very six months. Every two years (in April of even numbered years), they make a "long term service" (LTS) release. These releases are supposed to be more stable than normal, and Canonical provides security patches to them for five years instead of the normal two years. The latest 12.04 is an LTS release. LTS releases are geared toward people for whom predictable stability is more important than running a recent version of all their software. I am not such a person (at least not at home).
|A narwhal is a small, arctic whale with one tusk
I usually give each new release a month or so after it goes public in order for any nasty bugs to get resolved before I upgrade to it. This also allows time for the early adopters to post about their problems and solutions on various forums so that when I run into the problem and Google for it, I'll find the answer.
However, this winter, things were pretty busy, and I never got around to upgrading my desktop from 11.04 to 11.10. Next thing I knew, 12.04 was out. There's always some pain that comes with upgrading an OS, so I decided to get it all out of the way at once and do both OS upgrades back to back to get to the latest release. In retrospect, that was a wise move.
The first part of a Ubuntu upgrade (when it downloads the files) is unattended, but the installation of said packages is an interactive process. Whenever the installer finds that you've modified a config file from the older release, it prompts you for what to do about it (keep / overwrite / etc). If you want to finish your upgrade in a reasonable amount of time (3 hours for me), you need to sit there and wait for these prompts. I find it useful to keep a log file of everything it asks me about. I also keep both old & new copies of any file that I don't let it overwrite so that I can go back later & merge in any important differences.
So, about these specific upgrades. I won't give detailed instructions here, but will instead give you enough info to Google for the myriad of web sites that already discuss each issue. If Google's no help, you can always ask your question on the Ubuntu Forums, which are very active with user support.
|An oncelot is a medium-sized cat
First off, I hate Gnome3's new Unity interface. I hate it with a passion... no, "passion" is not a strong enough word. I hate it with every fiber of my being. I have lots of useful info in my top panel, and I don't want to give that up. Anyway, the first thing I do now is to install the "Gnome Classic" interface. I found that the new "lightdm" login screen would then present Gnome Classic as an option, but would not actually use it when selected. I had to install and configure the old "gdm" login screen in order to get Gnome Classic to stick.
Once in Gnome Classic, I found that right clicking on the panel no longer gave me the preferences menu. Turns out it's now <Alt> + left click. It also looks like you can no longer precisely position icons in the panel; you're now suck with packing them together tightly at the left, center, or right ends. I guess I can live with that.
The panel menus presented in 11.10's Gnome Classic are completely hosed. The old "System" main menu is now gone. The contents of its "Preferences" and "Administration" submenus are now all lumped together into an "Other" menu under the main "Applications" main menu. Huh? How did that make it through the QA process?
I have my desktop configured with four virtual workspaces laid out in a cube. I've configured Compiz so that when I run my mouse off one edge of the screen, it flips to the adjacent workspace. With 11.10, this was broken. Even though the settings appeared to be correct in "compizconfig-settings-manager," it wouldn't flip unless I clicked on the workspace switcher in the panel. When I tried to dis/enable the Desktop Cube in Compiz Config Settings Manager, that program segfaulted.
|A pangolin, or "scaly anteater,"
also resembles an armadillo
The 12.04 install went fine for 2.5 hours, then my X server crashed. All I had was the text console via <Ctrl>-<Alt>-<F1>. The install process was still running, and was prompting me about differences in the rsyslog.conf file, but I doubt that prompt was significant. Of course, without access to my X server and the shell from which the install was running, I was unable to answer its prompt. I didn't want to reboot mid-way through an install, as I had no idea what all had been upgraded and whether I'd have a usable system upon reboot. However, I couldn't get X to restart (via "service gdm restart"), so I rebooted anyway.
I then ran "dpkg --configure -a", then "apt-get dist-upgrade". In retrospect, I probably should have just killed off the upgrade process and run these two commands from the text console without rebooting, but no harm was done. Once finished, I rebooted again to make sure everything was stable and running the same release version.
Upon logging in to my graphical console, I found that Compiz' Desktop Cube was magically working again. The rearranged menu options were now put into sane places (their own sub-menus under "Applications" / "System Tools", which is still not as good as the 11.04 locations, but infinitely better than the 11.10 locations).
There were still some other problems left over from the 11.10 install that I never resolved. First, whenever I switch from one workspace to another via any method, the windows from the previous workspace briefly flash on the screen before the new workspace settles down. This is a well-known bug that hundreds of people have reported. It's on Gnome's list of things to fix, which means I just have to live with it for now.
Whenever a new application window appears, it was located in the upper left corner of the screen, with the new window's decorator bar located underneath the top panel of my screen. I had to <Alt>-click to drag it down to where I could see the window bar. Turning on "Place Windows" inside the "Window Management" section of Compiz Config Settings Manager fixed this problem.
I found that even though I had sloppy flocus set, my windows would auto-raise whenever the mouse hovered over them for one second or more. The only way I could find to turn this off was to install the "Unsettings" config utility from a third party repository. One of the settings that this allows you to change is the mouse-over auto-raise.
Once again, I found that I couldn't get the preferences menu for my panel or its apps. 12.04 changed the hot key once gain from <Alt>-right click to <Meta>-<Alt>-right click (or <Super>-<Alt>-right click). Just pick a hot key and stick with it already, OK?
Speaking of AfterShot Pro, I found that if a window is maximized (as ASP usually is when in use), and you flip to a different workspace, that maximized window gets automatically moved to workspace #1. If you then flip to workspace #1 and un-maximize it, the window will immediately relocate back to the workspace where it really belongs. If the window is manually stretched to fill the screen (but not actually maximized via the decorator bar button), this does not happen. This happens with Firefox, too. That will get really annoying when I'm in the midst of a photo editing session.
I've noticed that I can no longer drag windows from one workspace to another, either via the title bar or the workspace switcher. The only way I've found to move them is to click the title bar menu and select the workspace to which I want to move it. Very clunky. This is exacerbated by the fact that I frequently have windows change workspaces spontaneously if I'm trying to relocate them the wrong way.
And finally, I find the nearly-invisible scroll bar thumbs that run along the right side of most windows (like xterms & file browsers) to be nearly useless. You've got about 2 pixels in width in which to grab the thumb before the window border steals the mouse and tries to resize horizontally. Maybe this is due to my chosen window theme, but I've never seen this in the past.
Of course there were a few other configuration tweaks that I wanted to make, but those were all straightforward. The above were really the only things that gave me trouble.
Overall, I'm not really happy with 12.04, but I think it was a necessary evil, since I don't want to be saddled with increasingly out of date versions of critical libraries and other programs. This upgrade probably took longer than any other for me to return things to a usable state afterward (and I've been upgrading since 5.04).
Although I'm pretty well versed in the server side of Linux, I wouldn't consider myself an expert on the desktop GUI. I pretty much just get my system to work smoothly and then leave it there so I can get my real work done. Still, if you've got any questions, I'll give it my best shot. I'd love to hear about your experiences with upgrading versions. Speak up in the comments below!