I'm planning on switching to Ubuntu 18.04.2 on my MacBook Pro and I want to verify my download. I followed the steps from the Ubuntu tutorial and completed obtaining keys and getting a good signature, but then I got stuck on step which is to check ISO. Keep in mind I'm using the MacBook Pro terminal so maybe my function isn't correct? On step 6, it tells me to type out
sha256sum -c SHA256SUMS 2>&1 | grep OK
so I can compare the verified checksum to the iso. Nothing really happens or I get some weird errors, I tried many variations such as using sha256sum on the iso and using that hash replacing "sha256sum" in the ubuntu tutorial etc.
However, if I just use sha256sum on the iso file itself, it'll give me a hash. Then I use this hash and compare it to the SHA256SUMS file from ubuntu and it matches. So is it safe to say that I have a verified iso that ubuntu intended it to be?
Also, am I comparing what's in the SHA256SUMS file or the hash of this function "sha256sum SHA256SUMS". Sorry if my questions are everywhere as I am so new to this. Thanks!