The currently running (active) firmware was uploaded via the web interface. THEN and NOW the upgrade procedure via cli (tftp) gives the same result:
kettofszt-top#sh ver
Active-image: flash://system/images/image_tesla_hybrid_2.5.0.83_release_cisco_signed.bin
Version: 2.5.0.83
MD5 Digest: 07968d912499cff5e8b07fdc24779854
Date: 18-Jun-2019
Time: 16:49:35
Inactive-image: flash://system/images/image1.bin
Version: 2.4.0.94
MD5 Digest: 6f5be217100f34929986f2e93dd2d5e9
Date: 31-May-2018
Time: 02:39:58
kettofszt-top#boot system tftp://148.6.2.9/fw/cisco/image_tesla_hybrid_2.5.0.83_release_cisco_signed.bin
18-Jun-2019 06:49:43 %COPY-I-FILECPY: Files Copy - source URL tftp://148.6.2.9/fw/cisco/image_tesla_hybrid_2.5.0.83_release_cisco_signed.bin destination URL flash://system/images/image_tesla_hybrid_2.5.0.83_release_cisco_signed.bin
Copy: Error occurred when writing file
kettofszt-top#18-Jun-2019 06:49:43 %COPY-W-TRAP: The copy operation has failed
This device is the master unit of a ring-topology stack with 3 devices.
