Installation: Ubuntu20.04.1-desktop-amd64 iso fails on sha256sum test

[AUROBINDO MAJUMDAR]

I downloaded ubuntu-20.04.1-desktop-amd64.iso. I am from India and the browser shows that the download was from 'tifr.rs.in' -- your mirror in India?. I have downloaded twice on 14 Nov . Signature verification of the check sum file SHA256SUMS file is OK, but the command " sha256sum -c SHA256SUMS 2>&1" outputs error message -> "ubuntu-20.04.1-desktop-amd64.iso: FAILED". Looks like the mirror is broken. Earlier, I tried to upgrade from 18.04, but it did not work and I had to re-install Ubuntu 18.04.4. If I try to upgrade again I may have a non-working installation again.

[TheFu]

Please post the exact command and the exact output, and please wrap that in code tags.
We assume you've done a quick check that the ISO file is about the correct size, yes?


$ sha256sum -c ubuntu-mate-20.04-desktop-amd64.SHA256
sha256sum: ubuntu-mate-20.04-desktop-amd64.SHA256: no properly formatted SHA256 checksum lines found

That isn't the correct way. I don't know how other people do it, but I do this:

$ sha256sum ubuntu-mate-20.04-desktop-amd64.iso
a298764d9d2615c6fc5e99c7dddd9d7687f885821e6915c57d af9747b9c33445 ubuntu-mate-20.04-desktop-amd64.iso

$ more ubuntu-mate-20.04-desktop-amd64.SHA256
a298764d9d2615c6fc5e99c7dddd9d7687f885821e6915c57d af9747b9c33445
That's 2 separate commands. Then using my eyes, I check that the command output shows the same sha256sum, as it does above. Simple because I don't have to remember any magical incantation, just that sha256{tab} will get the correct program.

And to be extremely clear, both files used have to be in the CWD.

ubuntu-mate-20.04-desktop-amd64.iso
ubuntu-mate-20.04-desktop-amd64.SHA256


Don't worry that I'm using Mate version. This works for any distro, just change the filenames appropriately.

[AUROBINDO MAJUMDAR]

Thanks., but it did not work with iso image I had downloaded. I tried another mirror in India and that too failed checksum verification. Finally, downloaded via torrent and the sha256sum was OK.

[TheFu]

If the sha256sum doesn't match, then it is a bad download.

Seems you got a good one, so if this is solved, help the community out and use the "Thread Tools" button near the top to mark it that way. That way people searching for solutions will find this easier. Good thread title, BTW.

[ajgreeny]

It sounds as if downloading using a torrent client would be a better way for you to get the iso files, particularly if your network is poor.

A torrent client (transmission is the default in all Ubuntu systems) will take a failures of network in its stride and checks each packet of the large file as it is downloaded; if it detects a bad packet it will download that part again.