Linux Mint long boot after partition resize

Did you delete and recreate your SWAP partition? Its UUID changed, which needs to be reflected in the /etc/fstab, or the system will still try to locate it in the old place.

To get the new UUID:

blkid

Then

sudo nano /etc/fstab 

And replace the SWAP UUID. It's probably the same in Ubuntu.

Ubtuntu 16.04 change default desktop environment

First get the available desktop enviroments.

ls /usr/share/xsessions/

Let's say your output is: ubuntu.desktop and xfce.desktop

Then modify the following file:

 sudo nano /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf

To make xfce default, replace "ubuntu" with "xfce", save and reboot.