cli: Add setup and firstboot commands

This adds two new top-level commands: setup and firstboot.

Firstboot is pure-golang implementation of a service that runs some
commands once when a system first boots. You need to install this
service, and put the scripts to run in a special directory. This is
inspired by the virt-builder --firstboot mechanism.

Setup is a general purpose command that makes it easy to setup certain
facilities on a new machine. These include the mgmt package dependencies
it might need, a service to run it from, and the necessary service to
use the mgmt firstboot service as well.

All of this has been built to facilitate handoff between provisioning a
new machine and running configuration management on it.

setup/pkg.go

@@ -0,0 +1,144 @@
+// Mgmt
+// Copyright (C) 2013-2024+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+//
+// Additional permission under GNU GPL version 3 section 7
+//
+// If you modify this program, or any covered work, by linking or combining it
+// with embedded mcl code and modules (and that the embedded mcl code and
+// modules which link with this program, contain a copy of their source code in
+// the authoritative form) containing parts covered by the terms of any other
+// license, the licensors of this program grant you additional permission to
+// convey the resulting work. Furthermore, the licensors of this program grant
+// the original author, James Shubin, additional permission to update this
+// additional permission if he deems it necessary to achieve the goals of this
+// additional permission.
+
+package setup
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	cliUtil "github.com/purpleidea/mgmt/cli/util"
+	"github.com/purpleidea/mgmt/util"
+	distroUtil "github.com/purpleidea/mgmt/util/distro"
+)
+
+// Pkg is the standalone entry program for the pkg setup component.
+type Pkg struct {
+	*cliUtil.SetupPkgArgs // embedded config
+	Config                // embedded Config
+
+	// Program is the name of this program, usually set at compile time.
+	Program string
+
+	// Version is the version of this program, usually set at compile time.
+	Version string
+
+	// Debug represents if we're running in debug mode or not.
+	Debug bool
+
+	// Logf is a logger which should be used.
+	Logf func(format string, v ...interface{})
+}
+
+// Main runs everything for this setup item.
+func (obj *Pkg) Main(ctx context.Context) error {
+	if err := obj.Validate(); err != nil {
+		return err
+	}
+
+	if err := obj.Run(ctx); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Validate verifies that the structure has acceptable data stored within.
+func (obj *Pkg) Validate() error {
+	if obj == nil {
+		return fmt.Errorf("data is nil")
+	}
+	if obj.Program == "" {
+		return fmt.Errorf("program is empty")
+	}
+	if obj.Version == "" {
+		return fmt.Errorf("version is empty")
+	}
+
+	if obj.SetupPkgArgs.Distro == "" {
+		return fmt.Errorf("distro is empty")
+	}
+
+	return nil
+}
+
+// Run performs the desired actions. This generates a list of bash commands to
+// run since we might not be able to run this binary to install these packages!
+// The output (stdout) of this command can be run from a shell.
+func (obj *Pkg) Run(ctx context.Context) error {
+	cmdName := ""
+
+	packages, exists := distroUtil.ToBootstrapPackages(obj.SetupPkgArgs.Distro)
+	if !exists {
+		return fmt.Errorf("unknown distro")
+	}
+
+	// TODO: Consider moving cmdName into the util/distro package.
+	if obj.SetupPkgArgs.Distro == "fedora" {
+		cmdName = "/usr/bin/dnf --assumeyes install"
+	}
+	if obj.SetupPkgArgs.Distro == "debian" {
+		cmdName = "/usr/bin/apt --yes install"
+	}
+
+	if cmdName == "" {
+		return fmt.Errorf("no command name found")
+	}
+	if len(packages) == 0 {
+		return nil // nothing to do
+	}
+
+	cmdArgs := []string{}
+	cmdArgs = append(cmdArgs, packages...)
+
+	if !obj.SetupPkgArgs.Exec { // print, don't exec
+		cmd := ""
+		if obj.SetupPkgArgs.Sudo {
+			cmd += "sudo" + " "
+		}
+		cmd += cmdName + " "
+
+		cmd += strings.Join(cmdArgs, " ")
+
+		fmt.Printf("%s\n", cmd)
+		return nil
+	}
+
+	// Split off any bonus elements to the command...
+	realCmdName := strings.Split(cmdName, " ")
+	realCmdArgs := []string{}
+	realCmdArgs = append(realCmdArgs, realCmdName[1:]...)
+	realCmdArgs = append(realCmdArgs, cmdArgs...)
+	opts := &util.SimpleCmdOpts{
+		Debug: obj.Debug,
+		Logf:  obj.Logf,
+	}
+	return util.SimpleCmd(ctx, realCmdName[0], realCmdArgs, opts)
+}