I create a virtual machine in QEMU and install Ubuntu Server.

Then I write the .IMG disk onto a SSD with dd, and it works.

But when I write the .IMG onto a thumb (flash) drive, the boot menu does not see it.

Is booting from a thumb drive any different from booting from SSD

  • It shouldn't be any different with a modern hardware. Do you verify that your BIOS is correctly configured to boot from USB?
    – ceremcem
    Commented Feb 13, 2020 at 21:52

1 Answer 1


Mystery solved: the dd command:

dd if=ubuntu.img of=/dev/sdb bs=16M

needs a sync afterwards:


Or some syncing flags built into dd can be used. dd does not wait for buffered data to be actually written to the disk, by default.

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