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Another thing you can test is manually booting your Debian system from GRUB2 boot menu by reaching the command line. This way if you're lucky any error you get will be printed on the screen.
.. Indeed you're right. 'Operating System not found' is displayed once boot via GRUB command line. I suppose this is an interesting info. What happened ? How to correct this ?I check the UUID (via GRUB2 -> ls) it is identical as the one specified in the GRUB parameters.
Thanks for help. Bruno -- Linux Counter # 353844 https://linuxcounter.net/user/353844.html