How can I reinstall the Unity Launcher

[Udvarias Ur]

I'm a first time user of this list, though I have been an administrator 
of a number of lists using the Mailman software.

I have a problem I can not seem to solve, regardless of years of 
experience with AT&T Unix, SCO Unix, Interactive Unix, Unixware, and 
Irix. It seems to have been triggered by the same problem that Jim 
Byrnes and Colin Law encountered in October 2011.

* I read some of the help for Unity, to find a way to configure it.
* I found mention of the Compiz settings manager. (I don't remember the 
exact name.)
     So I installed it.
* After changing only it's size and position the Launcher ceased to 
behave properly.
* Even resetting all the variables to their defaults, from inside the 
Compiz settings manager,
     would not return the Launcher to it's default behaviour.

* I removed the launcher, intending to re-install it, to re-establish 
the default behaviour.
* Unfortunately I rebooted the system before I re-install the Launcher.
* Logging in at the GUI pops up a small dialogue that reads
         'Failed to load session "ubuntu"'
     with a
         Logout
     button.

* Now I can only get into the system as root in recovery mode.

* All my data is on second hard disk that can be accessed by both 
Windows and Ubuntu so I can
     re-install Ubuntu.
         * However I spent a lot of time installing software and 
configuring Ubuntu to work the way
             I want it to.
           So, I'd rather not go through that again, though if push came 
to shove I could start all
             over from scratch.

* I thought editing the .loginrc would get me back in so I could 
re-install the Launcher.
          * However, Ubuntu (Linux?) doesn't have one that I could find.

* With my Windows system I downloaded all the Unity 2d packages from 
ca.archive.ubuntu.org.
* Booting into the root console, mounting the Windows partition, 
changing directory to the location
     of the Unity 2d packages and running

     apt-get install unity-2d-launcher_4.12.0-0ubuntu1_i386.deb
or
     apt-get install unity-2d-launcher

returned

W: Not using locking for read only lock file /var/lib/dpkg/lock
E: Unable to write to /var/cache/apt/
E: The package lists or status file could not be parsed or opened.

What am I omitting or doing wrong?


Some more info, running

     apt-cache pkgnames unity

produced the following output

unity-asset-pool
unity
unity-2d
unity-2d-panel
unity-place-applications
unity-lens-gwibber
unity-2d-launcher
unity-lens-applications
unity-services
unity-scope-musicstores
unity-lens-music
unity-common
unity-2d-spread
unity-place-files
unity-lens-files
unity-greeter
unity-2d-places

So it seems that unity-2d-launcher is still in the cache.

-- 
Udvarias Ur

This letter was generated and sent from Thunderbird on Windows.