PROBLEM

The task bar panel is gone, disappeared or has been removed/unconfigured part of some configuration change as a result of an upgrade or update.  This is one issue I had when upgrading from Fedora 8 to Fedora 9 and was mostly due to extensive overhaul of the KDE 4.1/4.0 over it’s predecessor KDE 3.5.  The taskbar panel was missing and the UI software provided with KDE 4.0 did not appear to have any graphical option for reenabling it.  Unfortunately there appear to have been many KDE 3.5 features that appear disabled / removed alot of people enjoyed, this being one of them.  Here is how to enable it:

SOLUTION
The issue turned out to be with settings here in the /root/.kde/share/config/plasma-appletsrc file with regards to:

[Containments][1]
formfactor=0
geometry=0,0,205,47
location=0
locked=false
plugin=
screen=-1

Part of my issue was that I had ‘location=0‘ above when it should be set to either 1,2,3,4 and ‘plugin=‘ should have been ‘plugin=panel‘.  ‘screen=-1‘ should also be set to something meaningful like 0+ instead of -1.  This was enough to reenable the taskbar in KDE 4.0 though as of yet have not seen any UI equivalent.  Once I followed above steps, and restarted KDE the config file was regenerated by KDE and contained:

[Containments][2]
formfactor=2
geometry=0,824,1152,40
location=4
locked=false
plugin=panel
screen=0
size=32
transform=1,0,0,0,1,0,0,-1900,1

[Containments][2][Applets][3]
geometry=0,8,36,36
locked=false
plugin=launcher

[Containments][2][Applets][3][Configuration]
Height=499
Width=437

[Containments][2][Applets][4]
geometry=40,8,870,32
locked=false
plugin=tasks

[Containments][2][Applets][5]
geometry=914,8,40,32
locked=false
plugin=pager

[Containments][2][Applets][6]
geometry=958,8,30,32
locked=false
plugin=systemtray

[Containments][2][Applets][7]
geometry=992,8,32,32
locked=false
plugin=notifier

[Containments][2][Applets][8]
geometry=1028,8,120,44
locked=false
plugin=digital-clock

[General]
locked=false

Above resolved the issue in this case, however, here’s a second way and more details on how this can be done.  I’ve opted to move ‘plasma-appletsrc‘ out of the way to let KDE regenerate one for me thus enabling the taskbar I’ve been missing.  The reason why this worked is that I noticed that the original file that was there already (Presumably from KD 3.5) very messy and would require alot of editing.  The quicker solution, as in this case, would be to let KDE 4.0 regenerate the file:

$ cd /root/.kde/share/config/
$ mv plasma-appletsrc old.plasma-appletsrc
$ init 3 (Will log you out of KDE)
$ A shell will come up asking for login.  Relogin into the shell.
$ init 5 (To restart the X Server and relogin to KDE to see your changes)

Naturally, there may be issues with this.  If you have already customized your settings for the taskbar, you’ll have to carefully weigh the above and decide how to best apply to your own configuration.  Don’t forget to do your backups!  You can also edit the file yourself if you want to tweak the look of your desktop.  That’s certainly possible but is out of scope of this article.