Uninstall directions do not work

[raxod502-plaid]

Describe the bug

The instructions at this issue comment to uninstall Nix do not work.

Steps To Reproduce

$ sudo rm -rf /nix
rm: /nix/.Spotlight-V100: Operation not permitted
rm: /nix/.Trashes: Operation not permitted
rm: /nix: Resource busy

Expected behavior

The directory should have been deleted. Apparently, some additional step is required. As suggested later in the linked issue thread, I already tried mounting, unmounting, rebooting, but to no avail.

nix-env --version output

Not available since I am trying to uninstall and already deleted the binaries.

Additional context

macOS Catalina, 10.15.6

[abathur]

@raxod502-plaid It looks like (probably new in Catalina), macOS is requiring the Full Disk Access permission in order to modify these files.

Workaround (for anyone needing to remove these files to finish uninstalling Nix):

1. add the permission:

   • Run open -n "x-apple.systempreferences:com.apple.preference.security?Privacy_AllFiles" or manually open System Preferences > Security & Privacy > Full Disk Access

   • Unlock to make changes.

   • Add an exemption for either your terminal app or shell. I suspect the right program will already be in the list (unchecked--IIRC accessing protected files with a program should add it to the list), in which case you can just tick it's checkbox. If not, you'll need to click "+" and find it.

     I keep the exemption enabled myself, but you may want to remove it after you're done. It's intended to keep programs (whether legitimate, or malware) from accessing some sensitive files without your permission.

2. Re-run the uninstall command that failed (exact command differs between single-/multi-user installs).

Fixing this in the installer

The closest we can probably get to a real fix is either :

1. keeping macOS from creating these/proactively beating macOS to the punch
2. nudging all macOS users towards creating the exemption they'll need to uninstall during the installation process

I don't think the latter is worth exploring unless the former fails for some reason... mixed thoughts:

• It sounds like some people successfully block creation of .Trashes/ with something like touch /nix/.Trashes. Worth testing.
• We already add nobrowse to the mount settings in /etc/fstab, which does appear to disable spotlight indexing (can check this with mdutil -s /nix).
• For some reason nobrowse may both disable indexing but not suffice for keeping it from creating the .Spotlight-V100 directory. I'm not certain why, but I do have the spotlight directory on one of my test systems, but not on my main.
  • At one point I think we had something like sudo mdutil -i off /nix either in the install script, or in the documented recommendations. IIRC we removed it because it reports an error to the user that we couldn't figure out, and it seemed nobrowse was sufficient. Running this command might have some additional effect, even if there's an error. I may have installed my main system when this was still the recommended approach.
  • Back in April I identified another approach that we haven't tried (since nobrowse seemed sufficient), which is touch /nix/.metadata_never_index. It's worth confirming whether this keeps macOS from creating the file. Not sure if we need to fiddle file permissions?

[raxod502-plaid]

Thank you for the response! I really appreciate it. Unfortunately, while enabling the Full Disk Access permission fixes the Operation not permitted errors, it does not fix the Resource busy error:

$ sudo rm -rf /nix
rm: /nix: Resource busy

Does that require an additional step? Unmounting and re-mounting the Nix volume does not seem to affect this.

While investigating this, I discovered that I could delete the Nix volume via Disk Utility, which seemed prudent to follow as an uninstall step. However, I now receive this error message instead:

$ sudo rmdir /nix
rmdir: /nix: Read-only file system

[abathur]

The Catalina-specific install prints a set of Catalina-specific uninstall instructions; I think they are the gap here:

nix/scripts/create-darwin-volume.sh

Lines 106 to 113 in 2a7ea2e

	echo " ------------------------------------------------------------------ "
	echo " | This installer will create a volume for the nix store and |"
	echo " | configure it to mount at /nix. Follow these steps to uninstall. |"
	echo " ------------------------------------------------------------------ "
	echo ""
	echo " 1. Remove the entry from fstab using 'sudo vifs'"
	echo " 2. Destroy the data volume using 'diskutil apfs deleteVolume'"
	echo " 3. Remove the 'nix' line from /etc/synthetic.conf or the file"

I imagine you may also need to reboot for all of that to take.

[raxod502-plaid]

Yes, you are exactly right. Those steps successfully remove the /nix directory. Perhaps they can be added to the documentation? It certainly did not occur to me to save a copy of the installer output for reference later.

[sambacha]

Alternatively you can just use Disk Utilities

First ERASE
Second REMOVE
Third EMPTY TRASHBIN

Bring up Disk Utilities then go and remove

After deleting you can rm -rf ~/nix
running $ lsof +D /nix will show nothing, meaning it has been removed

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/anyone-up-for-picking-at-some-nix-onboarding-improvements/13152/6

[stale]

I marked this as stale due to inactivity. → More info

[jeff-hykin]

Still a problem on Monterey, there is no fstab cause volumes are handled differently, sudo vifs is empty except for comments. Probably needs diskutil specific commands to undo the changes in a script.

Whenever I get around to updating my uninstall script, I'll add M1/Monterey and post it here.

[abathur]

on Monterey, there is no fstab cause volumes are handled differently

@jeff-hykin This isn't true.

This issue is also quite old, and there are updated official uninstall instructions at https://nixos.org/manual/nix/stable/installation/installing-binary.html#macos.

If you have a Nix Store volume but don't see it in /etc/fstab, I suspect the cause is that you've run the installer more than once without following the uninstall instructions linked above first. The installer isn't idempotent, so it may have removed the store volume here

nix/scripts/create-darwin-volume.sh

Lines 517 to 543 in 3ae9467

	fstab_uninstall_prompt() {
	cat <<EOF
	During install, I add '${NIX_ROOT}' to /etc/fstab so that macOS knows what
	mount options to use for the Nix volume.
	EOF
	cp /etc/fstab "$SCRATCH/fstab.edit"
	# technically doesn't need the _sudo path, but throwing away the
	# output is probably better than mostly-duplicating the code...
	delete_nix_vol_fstab_line patch "$SCRATCH/fstab.edit" &>/dev/null
	# if the patch test edit, minus comment lines, is equal to empty (:)
	if /usr/bin/diff -q <(:) <(/usr/bin/grep -v "^#" "$SCRATCH/fstab.edit") &>/dev/null; then
	# this edit would leave it empty; propose deleting it
	if confirm_rm "/etc/fstab"; then
	return 0
	else
	echo "Remove nix from /etc/fstab (or remove the file)"
	fi
	else
	echo "I might be able to help you make this edit. Here's the diff:"
	if ! _diff "/etc/fstab" "$SCRATCH/fstab.edit" && ui_confirm "Does the change above look right?"; then
	delete_nix_vol_fstab_line /usr/sbin/vifs
	else
	echo "Remove nix from /etc/fstab (or remove the file)"
	fi
	fi
	}

and then fallen over before re-adding it later.

[jeff-hykin]

on Monterey, there is no fstab cause volumes are handled differently

@jeff-hykin This isn't true.

@abathur so.. ? maybe there is some way to add an /etc/fstab but mine doesn't exist

[jeff-hykin]

Thanks for the updated instructions though. It contains the diskutil command I was going to try to find on my own:

sudo diskutil apfs deleteVolume /nix

The CLI installer still gives outdated instructions though (the original issue). But if the CLI installer mentions that URL, "Looks like you already have Nix installed. If you need to uninstall Nix see: https://nixos.org/manual/nix/stable/installation/installing-binary.html#macos" then I think this issue can be closed.

[abathur]

/etc/fstab is a file the user can create for specifying volume mounts, not something the system will ship with or create for you. See man fstab.

(And like I said before, running the installer a 2nd time might explain why yours is missing despite having nix installed. )

[jeff-hykin]

running the installer a 2nd time might explain why yours is missing despite having nix installed

it does not. Which is why I was saying:

if the CLI installer mentions that URL, "Looks like you already have Nix installed. If you need to uninstall Nix see: https://nixos.org/manual/nix/stable/installation/installing-binary.html#macos" then I think this issue can be closed.

[abathur]

it does not... if the CLI installer mentions that URL

If re-running the installer does not explain what you reported (as opposed to your assertion that on Monterey "there is no fstab cause volumes are handled differently"), why would adding a message to the installer fix your problem?

Regardless of the cause in your case, I agree that CLI messaging around uninstall instructions should be better.

[jeff-hykin]

why would adding a message to the installer fix your problem?

This github issue ("Uninstall directions do not work"). I followed the uninstall directions, they result in errors, and I had to go hunting for the full install directions.

I agree that CLI messaging around uninstall instructions should be better

Then we're on the same page 👍 .
I don't know where the message is in the source code, but if someone links to it I'll make a PR that should close this

[abathur]

I followed the uninstall directions

Which ones?

I don't know where the message is in the source code

Which one?

You've never quoted a message or posted a log. The installer has changed somewhat since this old issue was opened. The message I quoted earlier in this thread is now only emitted if someone directly executes or sources scripts/create_darwin_volume.sh (i.e., it only prints in a legacy mode for people depending on directly running the old script; this is not how the normal installer does it). Aside from that message, the only other instructions mentioned in this issue are the OP's link to a 2017 comment on a different issue.

[jeff-hykin]

The installer has changed somewhat
Which one?

Latest nix installer as far as I'm aware
bash <(curl -Lk https://releases.nixos.org/nix/nix-2.11.1/install)

Following these instructions results in errors:

[abathur]

• nix/scripts/install-multi-user.sh

  Lines 114 to 147 in a6239eb

  	uninstall_directions() {
  	subheader "Uninstalling nix:"
  	local step=0
  	if poly_service_installed_check; then
  	step=$((step + 1))
  	poly_service_uninstall_directions "$step"
  	fi
  	for profile_target in "${PROFILE_TARGETS[@]}"; do
  	if [ -e "$profile_target" ] && [ -e "$profile_target$PROFILE_BACKUP_SUFFIX" ]; then
  	step=$((step + 1))
  	cat <<EOF
  	$step. Restore $profile_target$PROFILE_BACKUP_SUFFIX back to $profile_target
  	sudo mv $profile_target$PROFILE_BACKUP_SUFFIX $profile_target
  	(after this one, you may need to re-open any terminals that were
  	opened while it existed.)
  	EOF
  	fi
  	done
  	step=$((step + 1))
  	cat <<EOF
  	$step. Delete the files Nix added to your system:
  	sudo rm -rf /etc/nix $NIX_ROOT $ROOT_HOME/.nix-profile $ROOT_HOME/.nix-defexpr $ROOT_HOME/.nix-channels $HOME/.nix-profile $HOME/.nix-defexpr $HOME/.nix-channels
  	and that is it.
  	EOF
  	}

• nix/scripts/install-darwin-multi-user.sh

  Lines 78 to 86 in a6239eb

  	poly_service_uninstall_directions() {
  	echo "$1. Remove macOS-specific components:"
  	if should_create_volume && test_nix_volume_mountd_installed; then
  	nix_volume_mountd_uninstall_directions
  	fi
  	if test_nix_daemon_installed; then
  	nix_daemon_uninstall_directions
  	fi
  	}

[zimbatm]

The docs now include the manual uninstall steps: https://github.com/NixOS/nix/blob/master/doc/manual/src/installation/installing-binary.md#uninstalling

[AlaiY95]

Well I'll be damned, this worked! Never seen a pm so weird to uninstall. Thanks!

[LandonSchropp]

Here's the updated location of the macOS uninstallation instructions:

https://github.com/NixOS/nix/blob/master/doc/manual/src/installation/uninstall.md#macos