Rewrite init script in rust and fix non-shell CMDs

init/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "slim-init"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+base64 = "0.23"
+nix = { version = "0.31", features = ["mount", "fs", "process", "user", "reboot"] }