Ubuntu – How to check whether the installer is corrupt


I've been trying to install 14.04.1 Server using a bootable USB created using Rufus.
It has installed perfectly well on one machine, but on the next machine, which is ostensibly exactly the same hardware components, it keeps failing at the 'install software' stage.

I've retried a few times, re-made the bootable USB, downloaded the image again and all sorts! I've run memory tests, and changed the hard drive which made no difference. Once it even teased me by completing the software install, but failed to install grub.

I've used the 'test disc for defects' option, which normally returns './install/netboot/ubuntu-installer/i386/pxelinux.cfg/default has failed MD5checksum verification, the file or disc may be corrupt.' Though I'm not sure whether the fact it's on the bootable USB may be affecting this.

The image was downloaded on a windows 7 PC, though I'm not sure this is relevant.
It is also the only OS being installed on the host.

I appreciate that I've included a lot of background info, which may be irrelevant or confusing. The crux of my question is:

How can I independently verify whether the downloaded iso image is corrupt?

Best Answer

You can only check the ISO itself, not the USB drive...

To check the validity of the downloaded ISO file:

md5sum /PathToYourIso/FileName.iso 
8c271271c1d94a94a1d06248176e8eaf  /PathToYourIso/FileName.iso

and then check the weird number in the front (the checksum) with the one you have to find on the web site you downloaded the file from.

Use sha1sum if the web site provides these checksums.

In your case, I suspect a problem on the USB (but that's just a hunch) Try

dd if=/dev/zero of=/dev/YourUSBdev

to completely wipe it before formatting.

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