move uninstall instructions to a separate page

placed in a subsection of the binary install, the instructions are hard
to find. putting them in a separate page that is shown in the table of
contents should make it easier for users to find what they need when
they need it.

1 files changed, 159 insertions, 0 deletions

diff --git a/doc/manual/src/installation/uninstall.md b/doc/manual/src/installation/uninstall.md
new file mode 100644
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+# Uninstalling Nix
+
+## Single User
+
+If you have a [single-user installation](./installing-binary.md#single-user-installation) of Nix, uninstall it by running:
+
+```console
+$ rm -rf /nix
+```
+
+## Multi User
+
+Removing a [multi-user installation](./installing-binary.md#multi-user-installation) of Nix is more involved, and depends on the operating system.
+
+### Linux
+
+If you are on Linux with systemd:
+
+1. Remove the Nix daemon service:
+
+   ```console
+   sudo systemctl stop nix-daemon.service
+   sudo systemctl disable nix-daemon.socket nix-daemon.service
+   sudo systemctl daemon-reload
+   ```
+
+1. Remove systemd service files:
+
+   ```console
+   sudo rm /etc/systemd/system/nix-daemon.service /etc/systemd/system/nix-daemon.socket
+   ```
+
+1. The installer script uses systemd-tmpfiles to create the socket directory.
+    You may also want to remove the configuration for that:
+
+   ```console
+   sudo rm /etc/tmpfiles.d/nix-daemon.conf
+   ```
+
+Remove files created by Nix:
+
+```console
+sudo rm -rf /nix /etc/nix /etc/profile/nix.sh ~root/.nix-profile ~root/.nix-defexpr ~root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
+```
+
+Remove build users and their group:
+
+```console
+for i in $(seq 1 32); do
+  sudo userdel nixbld$i
+done
+sudo groupdel nixbld
+```
+
+There may also be references to Nix in
+
+- `/etc/profile`
+- `/etc/bashrc`
+- `/etc/zshrc`
+
+which you may remove.
+
+### macOS
+
+1. Edit `/etc/zshrc`, `/etc/bashrc`, and `/etc/bash.bashrc` to remove the lines sourcing `nix-daemon.sh`, which should look like this:
+
+   ```bash
+   # Nix
+   if [ -e '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh' ]; then
+     . '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh'
+   fi
+   # End Nix
+   ```
+
+   If these files haven't been altered since installing Nix you can simply put
+   the backups back in place:
+
+   ```console
+   sudo mv /etc/zshrc.backup-before-nix /etc/zshrc
+   sudo mv /etc/bashrc.backup-before-nix /etc/bashrc
+   sudo mv /etc/bash.bashrc.backup-before-nix /etc/bash.bashrc
+   ```
+
+   This will stop shells from sourcing the file and bringing everything you
+   installed using Nix in scope.
+
+2. Stop and remove the Nix daemon services:
+
+   ```console
+   sudo launchctl unload /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+   sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+   sudo launchctl unload /Library/LaunchDaemons/org.nixos.darwin-store.plist
+   sudo rm /Library/LaunchDaemons/org.nixos.darwin-store.plist
+   ```
+
+   This stops the Nix daemon and prevents it from being started next time you
+   boot the system.
+
+3. Remove the `nixbld` group and the `_nixbuildN` users:
+
+   ```console
+   sudo dscl . -delete /Groups/nixbld
+   for u in $(sudo dscl . -list /Users | grep _nixbld); do sudo dscl . -delete /Users/$u; done
+   ```
+
+   This will remove all the build users that no longer serve a purpose.
+
+4. Edit fstab using `sudo vifs` to remove the line mounting the Nix Store
+   volume on `/nix`, which looks like
+   `UUID=<uuid> /nix apfs rw,noauto,nobrowse,suid,owners` or
+   `LABEL=Nix\040Store /nix apfs rw,nobrowse`. This will prevent automatic
+   mounting of the Nix Store volume.
+
+5. Edit `/etc/synthetic.conf` to remove the `nix` line. If this is the only
+   line in the file you can remove it entirely, `sudo rm /etc/synthetic.conf`.
+   This will prevent the creation of the empty `/nix` directory to provide a
+   mountpoint for the Nix Store volume.
+
+6. Remove the files Nix added to your system:
+
+   ```console
+   sudo rm -rf /etc/nix /var/root/.nix-profile /var/root/.nix-defexpr /var/root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
+   ```
+
+   This gets rid of any data Nix may have created except for the store which is
+   removed next.
+
+7. Remove the Nix Store volume:
+
+   ```console
+   sudo diskutil apfs deleteVolume /nix
+   ```
+
+   This will remove the Nix Store volume and everything that was added to the
+   store.
+
+   If the output indicates that the command couldn't remove the volume, you should
+   make sure you don't have an _unmounted_ Nix Store volume. Look for a
+   "Nix Store" volume in the output of the following command:
+
+   ```console
+   diskutil list
+   ```
+
+   If you _do_ see a "Nix Store" volume, delete it by re-running the diskutil
+   deleteVolume command, but replace `/nix` with the store volume's `diskXsY`
+   identifier.
+
+> **Note**
+>
+> After you complete the steps here, you will still have an empty `/nix`
+> directory. This is an expected sign of a successful uninstall. The empty
+> `/nix` directory will disappear the next time you reboot.
+>
+> You do not have to reboot to finish uninstalling Nix. The uninstall is
+> complete. macOS (Catalina+) directly controls root directories and its
+> read-only root will prevent you from manually deleting the empty `/nix`
+> mountpoint.
+