lightdm not working and systems messed up

[lucacerone]

Dear all,
I messed up my computer and I think I uninstalled some important
package.
Now everytime I start up the graphical shell hangs
and I have to manually launch
sudo /etc/init.d/gdm restart
from a different shell.
After that if I try to start lightdm
or if I try to login in a Ubuntu (Unity) session
the launcher don't appear and the windows are broken.
I don't know why but I think that the kde-windows manager is used
instead of compiz/lightdm etc...

Can you please help me to restore my computer to a working state?
I have a lot of important stuffs on it and it would be a mess to
have to reinstall everything from scratch!

Thanks a lot in advance for your help,
Cheers, -Luca

[ymzn]

try this

sudo dpkg-reconfigure lightdm

https://wiki.ubuntu.com/LightDM (https://wiki.ubuntu.com/LightDM)

[lucacerone]

Thanks Ymzn.
Maybe you can help me: on askubuntu (http://askubuntu.com/questions/70572/reset-unity-and-gnome-to-default-values/70617#70617) I've been suggested to use:

sudo apt-get -o DPkg::options::=--force-confnew --reinstall install <package>

The problem is I don't know which are the packages that would need such a solution.
Can you help me?
Thanks a lot again!

[pt123]

sudo apt-get -o DPkg::options::=--force-confnew --reinstall install <package>
in this case the package is lightdm

so you get this

sudo apt-get -o DPkg::options::=--force-confnew --reinstall install lightdm


but I have tried this and it doesn't get lightdm to start