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How to boot from a live USB stick on a Mac

ng flag
Scottmeup

Is it possible to boot from a live USB stick on a Mac?

I created the USB stick using this tutorial, and I have tried a couple of different USB sticks as well as using both iso mode and DD mode in rufus.

Grub seems to be loading properly from the USB stick. I'm asked if I want to boot Ubuntu, Ubuntu with safe graphics, and a couple of other options. When I choose to boot Ubuntu from the menu my machine shows the ubuntu loading screen for a while, but after a while it displays a screen filled with lines of /init: line 49: can't open /dev/sdb: No medium found and at the bottom of the screen is Unable to find a medium container a live file system. Attempt interactive netboot from a URL?

I've previously booted into Ubuntu, and operating systems on external USB HDDs on this machine by installing rEFInd on the machine's internal storage. The machine's internal storage has an issue at the moment so I've been using the built in Startup Manager to select the USB volume that Ubuntu is installed on.

The SHA256 of the downloaded ubuntu-20.04.3-desktop-amd64.iso is correct.

md5sum -c md5sum.txt showed only one error: boot/grub/efi.img: FAILED edit: repeated this test with another USB stick and there were no MD5 errors, but the behavior is the same.

dmesg |grep squashfs showed only the copyright message.

The behavior is the same with the USB stick installed on every USB port on my machine.

The USB install boots to Ubuntu desktop when run in VMWare Player 16 via Plop Boot and PlopKexec

The USB boots to Ubuntu Desktop from a Lenovo Thinkcentre M700

I'm wondering if there's something else I can check? It seems that the booting process gets only so far but then loses track of the storage device. I'm not sure how I could check that it's even visible at all or not to the OS at that point, or if it becomes labelled as something different...?

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guiverc avatar
cn flag
guiverc
Your error "*No medium found*" is an error that occurs when the ISO was invalid (did you verify it? https://tutorials.ubuntu.com/tutorial/tutorial-how-to-verify-ubuntu#0) or the write to installation media was flawed (did the validation complete successfully? I bet it didn't, so you can use another box to run the test & if it fails there too, it's a bad write of the ISO).
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guiverc avatar
cn flag
guiverc
Does this answer your question? [Is verifying ISOs downloaded from the official website worthwhile?](https://askubuntu.com/questions/993407/is-verifying-isos-downloaded-from-the-official-website-worthwhile) FYI: I've written multiple answers on that question; the ISO validation is the most up-voted; but in my experience (*writing 300+ ISOs to media per annum*) it's the write to media that is most often flawed; my less upvoted additional answer, which is also found [here](https://askubuntu.com/questions/1311183/do-i-need-to-check-the-integrity-of-a-ubuntu-install)
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ng flag
Scottmeup
Hi @guiverc ! I think everything looks OK from what I could tell, I added the verification steps I've taken near the bottom of the question. The only outstanding check was the file `efi.img`s MD5 sum.
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guiverc avatar
cn flag
guiverc
If a single file has an error; the whole media is potentially invalid and should not be used (*even if you get it installed; it'll take you hours of effort to ensure the install is actually valid which it's just far more time efficient to ignore it & re-write the media correctly. In my experience about 5-8% of ISO writes fail because USB media is made to cost & consumable; fyi: the 5-8% assumes sandisk or a good brand; it's higher for cheaper media*)
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ng flag
Scottmeup
@guiverc ok :) got a good write according to md5sum's output on different media but the behavior is the same. Are there any other verification steps I can take?
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ng flag
Scottmeup
@karel I'm not sure about that link, it might be a bit out of date: I get as far as grub but some time after that the boot fails.
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Andra avatar
tr flag
Andra
maybe try another usb port
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ng flag
Scottmeup
Thanks @Andra :) gave it a shot but the behavior is still the same
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