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I wanted to upgrade from Ubuntu 16.04 to 17.04.
I created a bootable usb stick in Ubuntu 16.04 using Startup Disk Creator selecting the downloaded 17.04 iso.
I'm using a Kingston 8GB usb stick.
I can select the stick in the BIOS and boot menu, but the system keeps starting up as usual via the main start up disk. Ignoring the usb stick.
I'm reading similar posts about the matter, but I don't find a suitable answer.