docs: Add notes on Nix package manager installation and usage

random-thoughts/2025-01-02.md

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+---
+title: 
+date: 2025-01-02T00:03
+dg-publish: true
+dg-permalink: ""
+description: ""
+tags:
+  -
+---
+> 沒什麼組織、一些倏忽即逝有趣或不有趣的想法
+
+- Nix 初探
+  - Installation - https://nix.dev/install-nix
+    - `sh <(curl -L https://nixos.org/nix/install)`
+    - What it does:
+      - Install Nix package manager
+      - Create a new profile for the current user
+      - Add the Nix profile to the user's shell profile
+      - Based on the installation log, here are the critical changes Nix made to your machine:
+        - File System Changes: (this is because macOS now (starting in 10.15 Catalina) has a read-only root directory. To support Nix, it will create a volume and configure macOS to mount it at /nix)
+          Created a dedicated encrypted volume called "Nix Store" mounted at `/nix`
+          Modified `/etc/synthetic.conf` to create the mount point
+          Modified `/etc/fstab` to specify volume mount options
+        - User and Group Creation:
+          Created a system group called `nixbld` with GID 350
+          Created 32 system users (_nixbld1 through _nixbld32) with UIDs 351-382
+          All build users are:
+            Set to have /var/empty as home directory
+            Disabled from logging in
+            Added to the nixbld group
+            Hidden from the system
+        - Directory Structure:
+          Created several directories under /nix, including:
+          `install: mkdir /nix/var`
+          `install: mkdir /nix/var/log`
+          `install: mkdir /nix/var/log/nix`
+          `install: mkdir /nix/var/log/nix/drvs`
+          `install: mkdir /nix/var/nix`
+          `install: mkdir /nix/var/nix/db`
+          `install: mkdir /nix/var/nix/gcroots`
+          `install: mkdir /nix/var/nix/profiles`
+          `install: mkdir /nix/var/nix/temproots`
+          `install: mkdir /nix/var/nix/userpool`
+          `install: mkdir /nix/var/nix/daemon-socket`
+          `install: mkdir /nix/var/nix/gcroots/per-user`
+          `install: mkdir /nix/var/nix/profiles/per-user`
+          `install: mkdir /nix/store`
+          `install: mkdir /etc/nix`
+        - Shell Configuration:
+          Backed up and modified shell configuration files:
+          `/etc/bashrc`
+          `/etc/zshrc`
+          Added Fish shell configurations
+          Added Nix environment setup scripts to these files (e.g. execute `. '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh'`)
+        - System Services:
+          Created a LaunchDaemon at /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+          Set up a service to automatically mount the Nix volume
+        - Package Management:
+          Installed Nix package manager under `/nix/store/`
+          Set up the default profile with basic packages including SSL certificates (nss-cacert)
+
+          These changes make Nix work as a separate package manager on macOS, isolated from the rest of your system in its own volume.
+  - Usage
+    - `nix-shell -p <package>`: Start a shell with the specified package available
+    - `nix-shell -p <package> --command <command>`: Run a command in a shell with the specified package available
+    - `nix-shell -p <package> --run <command>`: Run a command in a shell with the specified package available and exit
+    - `nix-store --gc`: Garbage collect the Nix store to remove unused packages