User was added via
useradd command. So i'm unable to login using GUI as i do as @root. When i enter login and password for GUI seems linux accept them but instead to load desktop it becomes black for a second and force me back to login screen again.
There are two ways to add a user: useradd and adduser. The former, which you used, does do some things, like creating a line in /etc/passwd:
Code:
$ sudo useradd testme
$ grep testme /etc/passwd
testme:x:1001:1001::/home/testme:/bin/sh
But even though it creates the user, it doesn't do other helpful things like create a user directory.
My guess is that you can't log in locally because your GUI wants to be able to write into the home directory which doesn't exist. You should be using adduser instead, which will do things like create the user directory in /home and provide a password to the newly-created user.
More info at this StackExchange answer.