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lgautier
Asked: 2020-07-18 10:44:04 +0800 CST

Check error with 20.04-desktop ISO

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When using the ISO for Ubuntu 20.04, checking the SHA256SUM (from here - https://releases.ubuntu.com/20.04/SHA256SUMS), and creating a bootable USB, the following message appears briefly at the end of the media check during boot.

Check finished: errors found in 1 files! You might encounter errors.

I tried creating the bootable USB with 3 different thumbdrives (2 different brands), and using either the Startup Disk Creator or Disks and the error does not go away.

Could the ISO be corrupted ? (and the checksum be calculated on the corrupted iso).

edit: a comment requested further clarification on that latest part - The check during boot appears to be checking individual files (in the ISO) while the checksum verfied after downloading (and prior to creating the bootable USB) is for the ISO. The creation of the ISO and the calculation of its digest, and the check mechanisms for individual files in the ISO can be distinct processes, which would allow the creation of a corrupted ISO if being built from at least one corrupted subpart (file).

live-usb usb iso disk-check

1 Answers

  1. I checked all files in the ISO individually matched the MD5 checksum with the list of checksums in the ISO: the checksum does not match for one file: ./boot/grub/efi.img.

    This means that the ISO is incorrect. I filed an issue report on Launchpad: https://bugs.launchpad.net/ubuntu/+bug/1888033

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