[nix] Add nix install command (#337)

## Summary

This is a first step in having devbox install nix for you. This command
can help us iterate faster. It's currently hidden.

This adds `devbox nix install` which does exactly that, it attempts to
install nix. Right now all output/input is redirected to stdout/stdin
which means the user will control how the installation proceeds (nix
explains, prompts and requests sudo).

In follow ups we can improve this by:

* Requiring sudo up front
* Hiding prompts and answering them automatically.
* Detecting if nix is not installed and offering to install it when user
takes any step that requires it.

## How was it tested?

`devbox nix install`

Author: mikeland73

.golangci.yml

@@ -48,6 +48,7 @@ linters-settings:
       - ns string
       - r *http.Request
       - r io.Reader
+      - r *os.File
       - sh *Shell
       - sh *shell
       - sh *shell.Shell
@@ -56,6 +57,7 @@ linters-settings:
       - t testing.T
       - w http.ResponseWriter
       - w io.Writer
+      - w *os.File
   wrapcheck:
     ignorePackageGlobs:
       - go.jetpack.io/devbox/*

boxcli/root.go

@@ -34,6 +34,7 @@ func RootCmd() *cobra.Command {
 	command.AddCommand(PlanCmd())
 	command.AddCommand(RemoveCmd())
 	command.AddCommand(RunCmd())
+	command.AddCommand(SetupCmd())
 	command.AddCommand(ShellCmd())
 	command.AddCommand(VersionCmd())
 	command.AddCommand(genDocsCmd())

boxcli/setup.go

@@ -0,0 +1,32 @@
+// Copyright 2022 Jetpack Technologies Inc and contributors. All rights reserved.
+// Use of this source code is governed by the license in the LICENSE file.
+
+package boxcli
+
+import (
+	"github.com/spf13/cobra"
+	"go.jetpack.io/devbox/nix"
+)
+
+func SetupCmd() *cobra.Command {
+	setupCommand := &cobra.Command{
+		Use:    "setup",
+		Short:  "Setup devbox dependencies",
+		Hidden: true,
+	}
+
+	installNixCommand := &cobra.Command{
+		Use:   "nix",
+		Short: "Installs Nix",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return runInstallNixCmd()
+		},
+	}
+
+	setupCommand.AddCommand(installNixCommand)
+	return setupCommand
+}
+
+func runInstallNixCmd() error {
+	return nix.Install()
+}

nix/install.go

@@ -0,0 +1,45 @@
+package nix
+
+import (
+	_ "embed"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+
+	"github.com/pkg/errors"
+)
+
+//go:embed install.sh
+var installScript string
+
+func Install() error {
+	r, w, err := os.Pipe()
+	if err != nil {
+		return errors.WithStack(err)
+	}
+	defer r.Close()
+	defer w.Close()
+
+	cmd := exec.Command("sudo", "sh", "-c", installScript)
+	// Attach stdout but no stdin. This makes the command run in non-TTY mode
+	// which skips the interactive prompts.
+	// We could attach stderr? but the stdout prompt is pretty useful.
+	cmd.Stdin = nil
+	cmd.Stdout = w
+	cmd.Stderr = nil
+
+	fmt.Println("Installing Nix. This will require sudo access.")
+	if err = cmd.Start(); err != nil {
+		return errors.WithStack(err)
+	}
+
+	go func() {
+		_, err := io.Copy(os.Stdout, r)
+		if err != nil {
+			fmt.Println(err)
+		}
+	}()
+
+	return errors.WithStack(cmd.Wait())
+}

nix/install.sh

@@ -0,0 +1,119 @@
+#!/bin/sh
+
+# This script installs the Nix package manager on your system by
+# downloading a binary distribution and running its installer script
+# (which in turn creates and populates /nix).
+
+{ # Prevent execution if this script was only partially downloaded
+oops() {
+    echo "$0:" "$@" >&2
+    exit 1
+}
+
+umask 0022
+
+tmpDir="$(mktemp -d -t nix-binary-tarball-unpack.XXXXXXXXXX || \
+          oops "Can't create temporary directory for downloading the Nix binary tarball")"
+cleanup() {
+    rm -rf "$tmpDir"
+}
+trap cleanup EXIT INT QUIT TERM
+
+require_util() {
+    command -v "$1" > /dev/null 2>&1 ||
+        oops "you do not have '$1' installed, which I need to $2"
+}
+
+case "$(uname -s).$(uname -m)" in
+    Linux.x86_64)
+        hash=c6d48479d50a01cdfc3669440776692ca7094ff29028b1fec6da0abeead16a01
+        path=sicsy40akh9hs5r8iz1rkgnh46yfns4h/nix-2.11.1-x86_64-linux.tar.xz
+        system=x86_64-linux
+        ;;
+    Linux.i?86)
+        hash=37fa1567394baf7fac2651d4d60890191b9d183626faf2069c59dbc602136ac5
+        path=17s133r9xnvwkg7v6var7i24w2av285g/nix-2.11.1-i686-linux.tar.xz
+        system=i686-linux
+        ;;
+    Linux.aarch64)
+        hash=b8ef85ea43d30ed89fdd176d8b044c5d1301628a77886742ea3f684cd4dc6db3
+        path=fhi79b7zvz6np2rhld034qzpf7pfmb67/nix-2.11.1-aarch64-linux.tar.xz
+        system=aarch64-linux
+        ;;
+    Linux.armv6l_linux)
+        hash=7181889751cb83add9b4ef7ea6bd0adb90eb0cd8c78422315cc22e6a7188dafd
+        path=r44jpi4hki9llkznyxdl18a7f634an2p/nix-2.11.1-armv6l-linux.tar.xz
+        system=armv6l-linux
+        ;;
+    Linux.armv7l_linux)
+        hash=8550980d6001f42f5dd2e969a016304f3e659bdcd9146e04c18b02f5b63994cd
+        path=0kmd8q1g4gyw6pr474xp3nxs8mvyigqh/nix-2.11.1-armv7l-linux.tar.xz
+        system=armv7l-linux
+        ;;
+    Darwin.x86_64)
+        hash=16dac47e397ff9026af23f355cc84465a2af7ec56b65ddb52c8b124d700556b1
+        path=f0zhwzkvn5vv583mzbj0dqahzcajkglx/nix-2.11.1-x86_64-darwin.tar.xz
+        system=x86_64-darwin
+        ;;
+    Darwin.arm64|Darwin.aarch64)
+        hash=ddead2fa8ef6b9b58fec4ab12b460f802a962fff68fb1c8fa47c7b8b5739bc0b
+        path=d2gq40kvzckjmhwbbnh718w64v6zlr3m/nix-2.11.1-aarch64-darwin.tar.xz
+        system=aarch64-darwin
+        ;;
+    *) oops "sorry, there is no binary distribution of Nix for your platform";;
+esac
+
+# Use this command-line option to fetch the tarballs using nar-serve or Cachix
+if [ "${1:-}" = "--tarball-url-prefix" ]; then
+    if [ -z "${2:-}" ]; then
+        oops "missing argument for --tarball-url-prefix"
+    fi
+    url=${2}/${path}
+    shift 2
+else
+    url=https://releases.nixos.org/nix/nix-2.11.1/nix-2.11.1-$system.tar.xz
+fi
+
+tarball=$tmpDir/nix-2.11.1-$system.tar.xz
+
+require_util tar "unpack the binary tarball"
+if [ "$(uname -s)" != "Darwin" ]; then
+    require_util xz "unpack the binary tarball"
+fi
+
+if command -v curl > /dev/null 2>&1; then
+    fetch() { curl --fail -L "$1" -o "$2"; }
+elif command -v wget > /dev/null 2>&1; then
+    fetch() { wget "$1" -O "$2"; }
+else
+    oops "you don't have wget or curl installed, which I need to download the binary tarball"
+fi
+
+echo "downloading Nix 2.11.1 binary tarball for $system from '$url' to '$tmpDir'..."
+fetch "$url" "$tarball" || oops "failed to download '$url'"
+
+if command -v sha256sum > /dev/null 2>&1; then
+    hash2="$(sha256sum -b "$tarball" | cut -c1-64)"
+elif command -v shasum > /dev/null 2>&1; then
+    hash2="$(shasum -a 256 -b "$tarball" | cut -c1-64)"
+elif command -v openssl > /dev/null 2>&1; then
+    hash2="$(openssl dgst -r -sha256 "$tarball" | cut -c1-64)"
+else
+    oops "cannot verify the SHA-256 hash of '$url'; you need one of 'shasum', 'sha256sum', or 'openssl'"
+fi
+
+if [ "$hash" != "$hash2" ]; then
+    oops "SHA-256 hash mismatch in '$url'; expected $hash, got $hash2"
+fi
+
+unpack=$tmpDir/unpack
+mkdir -p "$unpack"
+tar -xJf "$tarball" -C "$unpack" || oops "failed to unpack '$url'"
+
+script=$(echo "$unpack"/*/install)
+
+[ -e "$script" ] || oops "installation script is missing from the binary tarball!"
+export INVOKED_FROM_INSTALL_IN=1
+"$script" "$@"
+
+} # End of wrapping