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Ubuntu 20.04 boot failure after editing system files on a iMac

in flag
Max1227

I'm a life-long Windows PC guy (boo hiss) whose friend was getting rid of a 2010 27-inch iMac (as the hard drive had failed). I took it from him and I figured I could use it as way to learn Linux. I bought an SSD and replaced the HD. Then I installed Ubuntu as a single install, deleting the Mac OS recovery partition in the process (which I now understand was a mistake).

Ubuntu 20.04 installed with no hiccups. Interestingly, when it boots I get nothing for 5 seconds, then the too-loud Mac start-up sound (more boo hiss), then a white screen for 10 seconds, then a black screen for 30 seconds, then the scrolling Ubuntu text starts. I gather this is normal for an old iMac running Ubuntu, but have no experience.

Anyway, I found a popular YouTube, 50 Things to Do After installing Ubuntu 20.04, and started to follow these guidelines. After finishing his 11th step yesterday, I shut the computer down for the evening. Some of his steps include decreasing the swap use by editing /etc/sysctl.conf and reducing SSD writes by editing fstab. I followed the instructions carefully.

This morning I started to continue the remaining steps from the YouTube video, but I could not get the machine to boot! I have tried Ctrl+C while booting and putting in a bootable flash drive, but neither have allowed me to boot from the flash drive or get to the Ubuntu GRUB boot loader.

Messages I am seeing include but are not limited to:

Failed to start Login Service
Failed to start Modem Manager
Failed to start Hostname Service
Failed to start Service for snap application
Failed to start Network Name Resolution
Failed to start Snap Daemon

Here is a screenshot of the boot errors:

enter image description here

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Organic Marble avatar
us flag
Organic Marble
Editing fstab can often lead to boot failure. What exactly did they suggest here "reducing SSD writes by editing fstab"?
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in flag
matigo
Just to confirm, are you running Ubuntu 20.04? To boot from the USB device, you'll want to hold the [Option] button down on the keyboard.
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user535733 avatar
cn flag
user535733
You will find that most folks here are adults who have long outgrown the childish OS/distro competition. No "boo, hiss". Please don't make us watch an entire random YouTube video to learn what you did -- take the time to tell us yourself. For most new users, you don't need to do ANYTHING extra after installing Ubuntu. Just use it. We pick a set of solid applications, test the heck out of them to make sure they are stable, and make sure all our default settings are sane, secure, and safe to use. When other good ideas come along, we incorporate them. Ubuntu is open-source and community-driven.
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in flag
Max1227
Organic Marble: Mod to fstab was to add "noatime." in front of errors=remount-ro 0
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in flag
Max1227
matigo: Ubuntu must not have drivers for wireless iMac keyboard because it did not work. I have been using an extra PC keyboard (ie no option key).
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in flag
Max1227
user535733: Was just trying to make the post a bit humorous - sorry you were offended. Regarding the other change, I added "vm.swappiness=10" at the bottom of the /etc/sysctl.conf file. Above is the mod to fstab. These were the only two file mods that I made.
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Organic Marble avatar
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Organic Marble
did you input `noatime` with a period after it? That is an error, I believe. https://tldp.org/LDP/solrhe/Securing-Optimizing-Linux-RH-Edition-v1.3/chap6sec73.html
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vn flag
Pablo Bianchi
Please start commenting out every line of `/etc/sysctl.conf` by adding a "`#`" at the beginning. Add to your post the fstab and any file you have changed. If you didn't have anything important you might just start from scratch again...
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in flag
Max1227
Organic Marble: Yes, you are correct. I was supposed to add ‘noatime,’ not ‘noatime.’ My bad. So, given that I can’t boot the iMac, does anyone have a suggestion to get it to read from the bootable USB? It did that when the SSD was unformatted. The only solution I can think of is removing the SSD, erasing it with my PC, and then inserting back into the iMac.
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Elon Musk
I sit in a Tesla and translated this thread with Ai:

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