I have followed various recommendations from the Ubuntu Documentation to create a bootable Ubuntu USB flash drive using the 12.04.1 Alternate install ISO-file for 64-bit PC. But the integrity test of the USB stick has failed and I do not see why.

These are the steps I have made:

1. Download of the 12.04.1 Alternate install ISO-file for 64-bit PC (ubuntu-12.04.1-alternate-amd64.iso) from http://releases.ubuntu.com/12.04.1/, as well as the MD5, SHA-1 and SHA-256 hash files and related PGP signatures
2. Verification of the data integrity of the ISO-file using the MD5, SHA-1 and SHA-256 hash files, after having verified the hash files using the related PGP signature files (see e.g. https://help.ubuntu.com/community/HowToSHA256SUM and https://help.ubuntu.com/community/VerifyIsoHowto)
3. Creation of a bootable USB stick using Ubuntu's Startup Disk Creator program (see http://www.ubuntu.com/download/help/create-a-usb-stick-on-ubuntu)
4. Boot of my computer using the newly made 12.04.1 Alternate install on USB stick
5. Selection of the option "Check disc for defects" (see https://help.ubuntu.com/community/Installation/CDIntegrityCheck)

Steps 1, 2, 3 and 4 went without any problem or error messages. However, step 5 ended with an error message entitled "Integrity test failed" and with the following content:

The ./install/netboot/ubuntu-installer/amd64/pxelinux.cfg/default file failed the MD5 checksum verification. Your CD-ROM or this file may have been corrupted.

I have experienced the same (might only be similar since I have no exact notes) error message in previous attempts using the 12.04 (i.e. not the maintenance release) Alternate install ISO-file. I have in these cases tried to install anyway and have so far not experienced any problems to my knowledge.

• Is failed integrity check described above a serious error?
• What is the solution?
• Or can it be ignored without further problems?