If you have installed the X Window System but are not seeing a graphical desktop environment once you log into your system, you can start the X Window System graphical interface using the command startx.

Once you enter this command and press Enter, the graphical desktop environment is displayed.

Note, however, that this is just a one-time fix and does not change the log in process for future log ins.

To set up your system so that you can log in at a graphical login screen, you must set the graphical systemd boot target as the default target. The system boots to the target described in the default.target file, which is a symbolic link (or symlink) to a specific target file.

Open a shell prompt. If you are in your user account, become root by typing the su command.

Now, type the following command to create a new symlink to the graphical target, which we will call default2:

   ln -s /lib/systemd/system/graphical.target /etc/systemd/system/default2.target 

Then, overwrite the current default.target symlink with the new symlink:

   mv /etc/systemd/system/default2.target /etc/systemd/system/default.target 

You will be prompted to confirm whether the file should be overwritten. Press y followed by Enter.

The next time you log in after rebooting your system, you are presented with a graphical login prompt.