Reinstalling on macos: "/nix: Read-only file system"

[00yk]

Describe the bug
After a broken uninstallation, I wasn't able to install nix.
Here are the error messages when I tried to reinstall using
sh <(curl -L https://nixos.org/nix/install) --daemon:

---- sudo execution ------------------------------------------------------------
I am executing:

    $ sudo mkdir -pv -m 0755 /nix /nix/var /nix/var/log /nix/var/log/nix /nix/var/log/nix/drvs /nix/var/nix /nix/var/nix/db /nix/var/nix/gcroots /nix/var/nix/profiles /nix/var/nix/temproots /nix/var/nix/userpool /nix/var/nix/gcroots/per-user /nix/var/nix/profiles/per-user

to make the basic directory structure of Nix (part 1)

mkdir: /nix: Read-only file system
mkdir: /nix/var: Read-only file system
mkdir: /nix/var/log: Read-only file system
mkdir: /nix/var/log/nix: Read-only file system
mkdir: /nix/var/log/nix/drvs: Read-only file system
mkdir: /nix/var/nix: Read-only file system
mkdir: /nix/var/nix/db: Read-only file system
mkdir: /nix/var/nix/gcroots: Read-only file system
mkdir: /nix/var/nix/profiles: Read-only file system
mkdir: /nix/var/nix/temproots: Read-only file system
mkdir: /nix/var/nix/userpool: Read-only file system
mkdir: /nix/var/nix/gcroots/per-user: Read-only file system
mkdir: /nix/var/nix/profiles/per-user: Read-only file system

Steps To Reproduce

1. I first install nix successfully(the first time),
2. then I tried to uninstall it using "sudo rm -rf /nix".
3. After that, I find there's still some files(starting with '.', I don't remember the exact names) left in /nix.
   So I use the "disk utitiliy.app" to uninstall the nix partition and do "sudo rm -rf /nix" again.

This time those remaining files were deleted but /nix(empty directory) is left.
When I try to do "sudo rm -rf /nix", it gives:

rm: /nix: Read-only file system

Expected behavior

Can someone points out a possible solution in my case to remove the empty directory /nix, thus I can reinstall nix?

[septemhill]

Had the same issue on Big sur

[abathur]

I think there's still a little bit of state lingering that is confusing the installer (FWIW this general category of issue will hopefully be fixed if/when #4289 is merged and released). Normally, the installer would prompt you to add the --darwin-use-unencrypted-nix-store-volume flag on macOS (and exit if it isn't present) when /nix doesn't exist.

EDIT/ATTENTION: The below advice was given in response to the original poster's indication that they had already removed the Nix volume from Disk Utility.

I think you need to:

1. look in /etc/synthetic.conf
   • if the file is absent or nix isn't mentioned in it, move to 2
   • if nix is the only thing present, you can remove it: sudo rm /etc/synthetic.conf
   • if other things are also present, you'll need to manually edit it out
2. reboot in order to nudge the system to remove the empty /nix directory

When you reinstall Nix (again, until #4289 lands), you'll need to add the --darwin-use-unencrypted-nix-store-volume flag.

[dsebban]

That did not work for me on Big Sur, anything else I can try ?

I am executing:

    $ sudo mkdir -pv -m 0755 /nix /nix/var /nix/var/log /nix/var/log/nix /nix/var/log/nix/drvs /nix/var/nix /nix/var/nix/db /nix/var/nix/gcroots /nix/var/nix/profiles /nix/var/nix/temproots /nix/var/nix/userpool /nix/var/nix/gcroots/per-user /nix/var/nix/profiles/per-user

to make the basic directory structure of Nix (part 1)

mkdir: /nix: Read-only file system
mkdir: /nix/var: Read-only file system
mkdir: /nix/var/log: Read-only file system
mkdir: /nix/var/log/nix: Read-only file system
mkdir: /nix/var/log/nix/drvs: Read-only file system
mkdir: /nix/var/nix: Read-only file system
mkdir: /nix/var/nix/db: Read-only file system
mkdir: /nix/var/nix/gcroots: Read-only file system
mkdir: /nix/var/nix/profiles: Read-only file system
mkdir: /nix/var/nix/temproots: Read-only file system
mkdir: /nix/var/nix/userpool: Read-only file system
mkdir: /nix/var/nix/gcroots/per-user: Read-only file system
mkdir: /nix/var/nix/profiles/per-user: Read-only file system

[abathur]

@dsebban No clue, without knowing what's on your system. Did you remove the Nix volume, as the OP stated they had, before following the instructions?

use the "disk utitiliy.app" to uninstall the nix partition

If so, a good start would be:

1. After removing the Nix volume, follow steps 1 & 2 in my previous post (but do not try to reinstall).
2. After the reboot, run the following and include the output here:
   • ls -la / /etc/{fstab,synthetic.conf}
   • diskutil list
   • diskutil info /nix

[dsebban]

I deleted using the disk utility and it worked, thanks !!!