Add exec command to cli

It is the entrypoint for box, to run commands with unshare

cmd/exec.go

@@ -0,0 +1,86 @@
+// Copyright © 2020 Ettore Di Giacinto <mudler@gentoo.org>
+//
+// 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 2 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 <http://www.gnu.org/licenses/>.
+package cmd
+
+import (
+	"os"
+
+	b64 "encoding/base64"
+
+	"github.com/mudler/luet/pkg/box"
+	. "github.com/mudler/luet/pkg/logger"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+)
+
+var execCmd = &cobra.Command{
+	Use:   "exec --rootfs /path [command]",
+	Short: "Execute a command in the rootfs context",
+	Long:  `Uses unshare technique and pivot root to execute a command inside a folder containing a valid rootfs`,
+	PreRun: func(cmd *cobra.Command, args []string) {
+		viper.BindPFlag("stdin", cmd.Flags().Lookup("stdin"))
+		viper.BindPFlag("stdout", cmd.Flags().Lookup("stdout"))
+		viper.BindPFlag("stderr", cmd.Flags().Lookup("stderr"))
+		viper.BindPFlag("rootfs", cmd.Flags().Lookup("rootfs"))
+		viper.BindPFlag("decode", cmd.Flags().Lookup("decode"))
+		viper.BindPFlag("entrypoint", cmd.Flags().Lookup("entrypoint"))
+
+	},
+	// If you change this, look at pkg/box/exec that runs this command and adapt
+	Run: func(cmd *cobra.Command, args []string) {
+
+		stdin := viper.GetBool("stdin")
+		stdout := viper.GetBool("stdout")
+		stderr := viper.GetBool("stderr")
+		rootfs := viper.GetString("rootfs")
+		base := viper.GetBool("decode")
+
+		entrypoint := viper.GetString("entrypoint")
+		if base {
+			var ss []string
+			for _, a := range args {
+				sDec, _ := b64.StdEncoding.DecodeString(a)
+				ss = append(ss, string(sDec))
+			}
+			//If the command to run is complex,using base64 to avoid bad input
+
+			args = ss
+		}
+		Info("Executing", args, "in", rootfs)
+
+		b := box.NewBox(entrypoint, args, rootfs, stdin, stdout, stderr)
+		err := b.Exec()
+		if err != nil {
+			Fatal(err)
+		}
+	},
+}
+
+func init() {
+	path, err := os.Getwd()
+	if err != nil {
+		Fatal(err)
+	}
+	execCmd.Hidden = true
+	execCmd.Flags().String("rootfs", path, "Rootfs path")
+	execCmd.Flags().Bool("stdin", false, "Attach to stdin")
+	execCmd.Flags().Bool("stdout", false, "Attach to stdout")
+	execCmd.Flags().Bool("stderr", false, "Attach to stderr")
+	execCmd.Flags().Bool("decode", false, "Base64 decode")
+
+	execCmd.Flags().String("entrypoint", "/bin/sh", "Entrypoint command (/bin/sh)")
+
+	RootCmd.AddCommand(execCmd)
+}