Backing up the configuration on a Cisco Wireless LAN Controller is not the same as Cisco IOS “copy startup-config”. I will show you how to do it with the GUI and CLI.
GUI: WLC > Commands > Upload File (Upload file from Controller) to your PC.
Press the Upload button to begin the backup.

Configuration saved on PC using Solarwinds TFTP Server
CLI
(Cisco Controller) >transfer upload mode tftp (Cisco Controller) >transfer upload datatype config (Cisco Controller) >transfer upload filename wlc-backup-2018 (Cisco Controller) >transfer upload path . (Cisco Controller) >transfer upload serverip 192.168.49.130 ! (Cisco Controller) >transfer upload start Mode............................................. TFTP TFTP Server IP................................... 192.168.49.130 TFTP Path........................................ ./ TFTP Filename.................................... wlc-backup-2018 Data Type........................................ Config File Encryption....................................... Disabled ************************************************** *** WARNING: Config File Encryption Disabled *** ************************************************** Are you sure you want to start? (y/N) y TFTP Config transfer starting. File transfer operation completed successfully.