Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Don’t format a drive of M1 Macs from recovery mode

giuliomagnifico.medium.com

Post reply on HN
Print view View original

21–30 of 154 posts

Re: Don’t format a drive of M1 Macs from recovery mode

#21

Post by jabberwcky »

wtallis wrote: post #19
jabberwcky wrote: post #8

Earlier quoted context omitted.

This option is horrendously inefficient on most modern drives. For many SSDs, issuing a secure erase request is an almost instantaneous process as it only requires the drive to generate a replacement encryption key, and need not even entail bulk writing or erasing physical flash pages

Writing 1 GB of zeros is also almost instantaneous. Even though it's overkill, writing 1 GB is hardly worth worrying about. Though I'd recommend also wiping the backup GPT at the end of the drive.

It is still bad advice, zero filling an SSD is not nearly the same as erasing it due to the presence of large (up to 10% or more of the drive) overprovisioning areas present in all devices, ignoring the permanent wear zero-filling the drive also causes, and the fact the controller believes real data remains stored, placing restrictions on its ability to perform internal maintenance

Re: Don’t format a drive of M1 Macs from recovery mode

#22

Post by rvz »

devit wrote: post #5

Why not just do the usual dd if=/dev/zero of= bs=1M count=1024 instead of using those weird proprietary tools?

You do realise if you get this wrong, you can't simply 'replace' the SSD on an Apple Silicon based Mac? You'll likely brick the device if the recovery partition is also wiped in the process.

It's back to the Apple Store for you.

Re: Don’t format a drive of M1 Macs from recovery mode

#23

Post by SXX »

I still can't access recovery mode because I had the same issue in attempt to setup proper Full-Disk-Encryption (no, you can't do that on M1 and need to use special encrypt user instead).

Recovery know I have OS installed, but because it's not installed the same way it no longer able to find credentials for authentification. And yeah I don't have second Macbook to properly factory reset it.

Along the way I stuck into 3 huge bugs and experience was terrible. Fortunatelly Apple support page actually show how to bypass it's bugs with command line magic which is easy for me as Linux nerd.

Re: Don’t format a drive of M1 Macs from recovery mode

#25

Post by digi59404 »

This is because the author didn't delete the entire volume group. You have to delete the whole volume group, i.e. erase the entire drive and it's partitions to reinstall OSX.

This isn't new with the M1 Macs. This has been a thing since they introduced APFS. When they went into disk utility after the cli - Then they could delete everything and kick off the OSX Install.

If the APFS Volume Group still exists the installer will try to unencrypt and work with it. So.. In short, just make sure you delete the volume group. There's a specific button for it. I just did this yesterday on a T2 Mac.

Re: Don’t format a drive of M1 Macs from recovery mode

#26

Post by kuschku »

volta83 wrote: post #16
fouc wrote: post #10

>Uff…what a paintful process! If an issue takes less than 5 different attempts to resolve and under 1-2 hours to fix, that can't really be called painful, merely annoying. Especially when it's only a one-time problem.

If your bar is "I want to do X, let's start by reading the Arch Wiki", then sure. If your bar is "It just works", then for me at least, if it takes me more than 1 minute I'd describe it as painful. My mother would describe anything that's not immediately obvious as painful.

The year of linux on the desktop won't happen because linux becomes more user friendly, but because macOS and windows 10 become less user friendly.

Re: Don’t format a drive of M1 Macs from recovery mode

#27

Post by wtallis »

albertopv wrote: post #15

Now imagine this happened on MS Windows...Shit MS, Windows sucks, etc. Reality is all OS have issues, pros and cons.

Windows and macOS are both very reluctant to tell the user what's actually happening on their disk. They both insist on abstractions that hide the reality of how partitions and filesystems are arranged behind the scenes. Sometimes that's a useful simplification, but sooner or later hiding that information from the user always leads to the OS lying about whether a device or filesystem is truly empty.

Re: Don’t format a drive of M1 Macs from recovery mode

#28

Post by Jonnax »

liminalsunset wrote: post #13

Big Sur appears to have introduced several new security features that complicate this process. I attempted a wipe on my 2019 16" Intel MBP to upgrade to Big Sur.... and after this, it required you to do something like sign in with a user to disable startup security, because it would not trust its own official Big Sur installer due to signatures maybe.

I think the reasoning is that it's to prevent a stolen laptop from being stolen, wiped and resold without the owner allowing it through their credentials.

I remember a poster on HN saying that after some exploit for the T2 security chip came out, they were making money from being paid by thieves to use the exploit to wipe the devices.

Of course they said they don't ask any questions which as we all know is an iron clad defence lol

Re: Don’t format a drive of M1 Macs from recovery mode

#29

Post by wtallis »

jabberwcky wrote: post #21
wtallis wrote: post #19

Earlier quoted context omitted.

Writing 1 GB of zeros is also almost instantaneous. Even though it's overkill, writing 1 GB is hardly worth worrying about. Though I'd recommend also wiping the backup GPT at the end of the drive.

It is still bad advice, zero filling an SSD is not nearly the same as erasing it due to the presence of large (up to 10% or more of the drive) overprovisioning areas present in all devices, ignoring the permanent wear zero-filling the drive also causes, and the fact the controller believes real data remains stored, placing restrictions on its ability to perform internal maintenance

It's fine advice. The wear of writing 1GB of zeros can and should be ignored. It's insignificant. And the drive's spare area is only relevant if you're trying to thoroughly wipe sensitive information from a device before disposing of it. But right now we're just trying to make a device appear functionally empty so that we can re-install an OS without remnants of any previous installation getting in the way. This does not require the (sometimes dubious) security assurances of a secure erase command.

Re: Don’t format a drive of M1 Macs from recovery mode

#30

Post by SXX »

SXX wrote: post #23

I still can't access recovery mode because I had the same issue in attempt to setup proper Full-Disk-Encryption (no, you can't do that on M1 and need to use special encrypt user instead). Recovery know I have OS installed, but because it's not installed the same way it no longer able to find credentials for authentification. And yeah I don't have second Macbook to properly factory reset it. Along the way I stuck into…

Apple support page that I reffering to:

https://support.apple.com/en-us/HT211983

You even have to go through "Erase Mac" twice in process. It's only work if you reboot it properly after each time which is not mentioned on support page. Such a mess.

Post reply on HN