Add grub edit var command (#846)

main.go

@@ -818,6 +818,104 @@ The validate command expects a configuration file as its only argument. Local fi
 			return action.ListBootEntries(cfg)
 		},
 	},
+	{
+		Name:  "grubedit",
+		Usage: "grubedit [set] KEY=VALUE",
+		Description: "Show or edit grub variables.\n\n" +
+			"Use `grubedit set KEY=VALUE` to set a grub variable. If the value is empty, it will remove the variable.\n\n" +
+			"Use `grubedit` to list all the grub variables found in the grub environment file.",
+		Action: func(c *cli.Context) error {
+			config, err := agentConfig.Scan(collector.Directories(constants.GetUserConfigDirs()...), collector.NoLogs, collector.StrictValidation(c.Bool("strict-validation")))
+			if err != nil {
+				return err
+			}
+			grubEnv := c.String("grub-file")
+			if _, err := config.Fs.Stat(grubEnv); err != nil && os.IsNotExist(err) {
+				// If file doesn't exist, we just log it and return
+				// Is not really an error, its just that there is no file so no vars are set
+				config.Logger.Logger.Info().Msgf("No file %s found", grubEnv)
+				return nil
+			}
+			vars, err := utils.ReadPersistentVariables(grubEnv, config)
+			if err != nil {
+				config.Logger.Logger.Error().Err(err).Msgf("Error reading grub variables from %s", grubEnv)
+				return err
+			}
+			if len(vars) == 0 {
+				config.Logger.Logger.Info().Msgf("No grub variables found in %s", grubEnv)
+			} else {
+				// Format the variables into a nice aligned list
+				maxKeyLen := 0
+				for k := range vars {
+					if len(k) > maxKeyLen {
+						maxKeyLen = len(k)
+					}
+				}
+				var b strings.Builder
+				for k, v := range vars {
+					b.WriteString(fmt.Sprintf("%-*s = %s\n", maxKeyLen, k, v))
+				}
+				config.Logger.Logger.Info().Msgf("Grub variables found in %s:\n%s", grubEnv, b.String())
+			}
+			return nil
+		},
+		Subcommands: []*cli.Command{
+			{
+				Name:      "set",
+				Usage:     "Add or Edit a grub variable. Setting an existing variable to an empty value will remove it",
+				UsageText: "grubedit set KEY=VALUE",
+				Before: func(c *cli.Context) error {
+					if c.Args().Len() != 1 {
+						cli.HelpPrinter(c.App.Writer, "File and key=value arguments missing\n\n", c.Command)
+						_ = cli.ShowSubcommandHelp(c)
+						return fmt.Errorf("")
+					}
+					return nil
+				},
+				Action: func(c *cli.Context) error {
+					config, err := agentConfig.Scan(collector.Directories(constants.GetUserConfigDirs()...), collector.NoLogs, collector.StrictValidation(c.Bool("strict-validation")))
+					if err != nil {
+						return err
+					}
+
+					// Transform the key=value argument into a map
+					parts := strings.SplitN(c.Args().First(), "=", 2)
+					vars := make(map[string]string)
+					if len(parts) != 2 {
+						return fmt.Errorf("key=value argument must be in the format KEY=VALUE")
+					}
+					if parts[1] == "" {
+						// If the value is empty, we remove the variable
+						vars[parts[0]] = ""
+					} else {
+						// Otherwise we set the variable to the value
+						vars[parts[0]] = parts[1]
+					}
+
+					grubEnv := c.String("grub-file")
+					err = utils.SetPersistentVariables(grubEnv, vars, config)
+					if err != nil {
+						config.Logger.Logger.Error().Err(err).Msgf("Error setting grub variables in %s", c.Args().First())
+						return err
+					}
+					if parts[1] == "" {
+						config.Logger.Logger.Info().Msgf("Removed grub variable %s from %s", parts[0], grubEnv)
+					} else {
+						config.Logger.Logger.Info().Msgf("Set grub variable %s=%s in %s", parts[0], parts[1], grubEnv)
+					}
+
+					return nil
+				},
+			},
+		},
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:  "grub-file",
+				Usage: "Path to the grub environment file to list or set variables to/from.",
+				Value: filepath.Join(constants.OEMPath, constants.GrubEnv),
+			},
+		},
+	},
 	{
 		Name:        "sysext",
 		Usage:       "sysext subcommands",

pkg/constants/constants.go

@@ -27,6 +27,7 @@ import (
 const (
 	GrubConf                     = "/etc/cos/grub.cfg"
 	GrubOEMEnv                   = "grub_oem_env"
+	GrubEnv                      = "grubenv" // grubenv is a file used by grub to store environment variables. Goes into OEM so its runtime modifiable
 	GrubDefEntry                 = "Kairos"
 	DefaultTty                   = "tty1"
 	BiosPartName                 = "bios"

pkg/utils/grub.go

@@ -474,6 +474,9 @@ func ReadPersistentVariables(grubEnvFile string, c *agentConfig.Config) (map[str
 		if strings.HasPrefix(a, "#") {
 			continue
 		}
+		if a == "" {
+			continue
+		}
 		splitted := strings.Split(a, "=")
 		if len(splitted) == 2 {
 			vars[splitted[0]] = splitted[1]