SLES and openSUSE by default sets to automatically log in user without having to authenticate with username and password. While convenient, this is a security risk as anyone with physical access to your machine could simply boot it up and access your account.
The option is set up during the installation process but if you've missed that or just simply want to change the setting after the fact, you could still do it via YaST or the command line.
> sudo nano /etc/sysconfig/displaymanager
## Type: string ## Default: # # Define the user whom should get logged in without request. If string # is empty, display standard login dialog. # DISPLAYMANAGER_AUTOLOGIN="user"
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