How do I generate a SHA256 sum on a Mac?

[1nuBJim]

The instructions either assume that I am already running Linux, or else refers me to instructions for Windows. I actually do have Linux set up on a computer that was giving me increasingly worse problems to the point that I am now no longer able to sign in on it. I got a MacBook Air Catalina from a friend, and spent most of a day figuring out how to use a Mac. I'm now trying to setup Linux Mint Cinnamon 20.1 on it, but I keep running into frustration after frustration, and I really hope someone can help me with this. My main concern right now is getting Linux on the Mac, but if you know of a simple fix for my other computer, I'd really appreciate that as well. I figure I'll have to submit another question about it after I get the Mac straightened out.

[xenopeek]

macOS has a builtin shasum command that can also do SHA256 sum like so:
shasum -a 256 /path/to/file

Run it from the terminal program. I'm not otherwise familiar with macOS but hope its file manager has the option to "open terminal here" like on Linux Mint so you can open the terminal immediately in the directory where you have the ISO file and just need to shasum -a 256 filename.

[1nuBJim]

I really appreciate you working on helping me, but I'm not there yet. I've got a real steep learning curve, since I knew practically nothing about Macs. I finally found out how to open Terminal, and a little bit about how to use it as well as finding the Mac equivalent of File Manager. I copied and pasted the first part of the command you gave me, and instead of /path/to/file I substituted ~/ISO, so it looked like: jim@Jims-MacBook-Air ~ % shasum -a 256 ~/ISO. The ~ apparently represents my home folder which is where I put the ISO file containing the three downloaded files. I then hit enter and got this result:
shasum: /Users/jim/ISO:
jim@Jims-MacBook-Air ~ %
That doesn't look anything like the sha256sum.txt which is: bc99cf204595d6a70a91e8306eb0afd99318216cb7bb2d6ec10b214c1629e2eb *linuxmint-20.1-cinnamon-64bit-beta.iso
43c704c9a216b802f7483d34e158de8ea505bfd29f48623b771853e3e6764a43 *linuxmint-20.1-mate-64bit-beta.iso
de75b825dbf458760fe35f9e71abd6ff743ef59c2242c6122843f66c1387ae45 *linuxmint-20.1-xfce-64bit-beta.iso

So, please tell me what I did wrong. Thanks!

[xenopeek]

I copied and pasted the first part of the command you gave me, and instead of /path/to/file I substituted ~/ISO, so it looked like: jim@Jims-MacBook-Air ~ % shasum -a 256 ~/ISO. The ~ apparently represents my home folder which is where I put the ISO file containing the three downloaded files.

Add the filename you want to sha256sum as in shasum -a 256 ~/ISO/linuxmint-20.1-cinnamon-64bit-beta.iso. Or wildcard it as in shasum -a 256 ~/ISO/*.iso.

Also I would suggest you download the release version of the ISO if indeed you currently have the beta version.

[1nuBJim]

It just doesn't seem to be working for me! Here is what I put in, along with the results:

jim@Jims-MacBook-Air ~ % shasum -a 256 ~/ISO/linuxmint-20.1-cinnamon-64bit-beta.iso
shasum: /Users/jim/ISO/linuxmint-20.1-cinnamon-64bit-beta.iso:
jim@Jims-MacBook-Air ~ %

I just got the only version that was available to me. I have no idea how to get a different version.

[1nuBJim]

@xenopeek seems to have given up on trying to help me, not that I can say I blame him/her. Here is my latest attempt, with the results which still don't seem to match the sha256sum.txt.

jim@Jims-MacBook-Air ~ % shasum -a 256 /Users/jim/ISO/linuxmint-20.1-cinnamon-64bit.iso
14f73c93f75e873f4ac70b6cddc83703755c2421135a8fbbfd6ccfeed107e971 /Users/jim/ISO/linuxmint-20.1-cinnamon-64bit.iso
jim@Jims-MacBook-Air ~ %

I dragged and dropped the ISO file to Terminal to obtain the path, and it doesn't say anything about it being a beta version. That leads me to believe that I may have the wrong .txt file. Yup, that was apparently the case, though I'm not sure how that happened. The above string of figures, by manual eyesight, matches the second line of figures in the new .txt file, which I figure is the correct line for me. However, that leaves me wondering what I'm supposed to do with the sha256sum.txt.gpg.txt file? Since I don't understand what the instructions mean by, "Import the Linux Mint signing key", does anyone want to clarify that for me, before I proceed further? Please note that I'm on a MacBook Air which I'm not very familiar with, plus I'm pretty sure the instructions at https://linuxmint.com/verify.php aren't written for.

[Pierre]

@xenopeek won't have given up - - but he does have an Life outside of these forums.

like all of us, xenopeek comes & goes as he can, as determined by his lifestyle.

there is also an limit to how we can guide folks into getting an working LinuxMint ISO file
and then being able to write that LinuxMint ISO file to an usb stick.
https://dyclassroom.com/howto-mac/how-t ... sha256-etc
thus, if you now have such an LinuxMint ISO file, then try writing it to an usb stick,
to see if it will Boot Up correctly, or not .. why .. you might ask ? when I'm not sure of it's authenticity ?.

- - you have to at some point, whether you are sure of it's, or whether you are not so sure of it.

[1nuBJim]

Thank you, Pierre. Now I'm having a problem creating a bootable USB. I downloaded Etcher, ran it supposedly to create a bootable drive, but it wasn't bootable, or even recognizable by the Mac. Any ideas on how to handle that? I seem to be having way too many problems!

[Pierre]

is the usb drive itself recognised by your iMac ?.

[sanmig]

I downloaded Etcher, ran it supposedly to create a bootable drive, but it wasn't bootable, or even recognizable by the Mac.

[ For the authentication you’d need to have GPG installed on your Mac and the Linux Mint signing key imported into it. Look in your Mac’s “Applications” if the "GPG Keychain.app" is there. ]

Etcher will do … But Catalina can not read the (isofs) Mint boot USB ("… disk … was not readable" message).
Likely your problem is to boot from USB, see https://support.apple.com/guide/mac-hel ... /mac/10.15
Does your MacBook Air have a T2 chip? You may open a can of worms …
https://support.apple.com/en-us/HT208862