Automatically generate, store, and subsequently load a VM UUID in the VM's run dir if not specified.

Author: bensallen

TODO.md

@@ -2,15 +2,13 @@
 
 ## Features
 
-- Add CI, CircleCI, clean code, etc.
 - Add dependency graph ordering
 
 ### Config
 
 - Reorganize internal/config to move VM action logic outside of config, eg. vm/vm.go
 - Generate HDD if it doesn't already exist
-- Generate UUID if not specified, store in .run/vm/<name>/uuid
-- Generate MAC for tap interfaces if not specified, store in .run/vm/<name>/<net>_mac
+- Generate MAC for tap interfaces if not specified, store in .run/vm/\<name\>/\<net\>_mac
 - Check write privs on run_dir, pid, and tty in Validate()
 - Check write privs on hdd, read privs on cdrom
 - Add template support for kexec cmdline for IP, ssh public
@@ -77,4 +75,6 @@ cmd: ifconfig bridge1 192.168.99.1 netmask 0xffffff00
 - If one of the tap interfaces doesn't come up, still add the ones that do come up to the bridge
 - Make relative paths be relative to the config file.
 - Make relative paths in a VM config relative to the run_dir
-- Add pid in status output
+- Add pid in status output
+- Add CI, CircleCI, clean code, etc.
+- Generate UUID if not specified, store in .run/vm/\<name\>/uuid

go.mod

@@ -4,6 +4,7 @@ go 1.12
 
 require (
 	github.com/BurntSushi/toml v0.3.1
+	github.com/google/uuid v1.1.1
 	github.com/integrii/flaggy v1.2.1-0.20190517180110-07ea7eb77404
 	github.com/kr/pretty v0.1.0
 	github.com/mitchellh/go-ps v0.0.0-20190716172923-621e5597135b

go.sum

@@ -1,5 +1,7 @@
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
+github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/integrii/flaggy v1.2.1-0.20190517180110-07ea7eb77404 h1:RlJzIvFdjZXuVrJqvPkzlaVq6q4AAyrjYYy+exCBWjM=
 github.com/integrii/flaggy v1.2.1-0.20190517180110-07ea7eb77404/go.mod h1:tnTxHeTJbah0gQ6/K0RW0J7fMUBk9MCF5blhm43LNpI=
 github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=

internal/config/config.go

@@ -22,10 +22,13 @@ func (c *Config) UpdateRelativePaths() {
 }
 
 // Defaults sets default values for unset variables in the config.
-func (c *Config) Defaults() {
+func (c *Config) Defaults() error {
 	configDir := filepath.Dir(c.Path)
 
 	for name := range c.VM {
-		c.VM[name].defaults(configDir, name)
+		if err := c.VM[name].defaults(configDir, name); err != nil {
+			return err
+		}
 	}
+	return nil
 }

internal/config/vm.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"syscall"
 
+	"github.com/google/uuid"
 	"github.com/mitchellh/go-ps"
 )
 
@@ -188,6 +189,23 @@ func pidFile(path string) (int, error) {
 	return pid, nil
 }
 
+func uuidFile(path string) (uuid.UUID, error) {
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		return [16]byte{}, fmt.Errorf("uuid file not found")
+	}
+	uuidTxt, err := ioutil.ReadFile(path)
+	if err != nil {
+		return [16]byte{}, fmt.Errorf("uuid file cannot be read")
+	}
+
+	uuid, err := uuid.Parse(string(uuidTxt))
+	if err != nil {
+		return [16]byte{}, fmt.Errorf("uuid file does not contain an UUID")
+	}
+
+	return uuid, nil
+}
+
 func (v *VMConfig) Cli() []string {
 
 	var args []string
@@ -266,10 +284,30 @@ func (v *VMConfig) Validate() error {
 	return nil
 }
 
-func (v *VMConfig) defaults(configDir string, name string) {
+func (v *VMConfig) defaults(configDir string, name string) error {
 	if v.RunDir == "" {
 		v.RunDir = filepath.Join(configDir, ".run/vm/", name)
 	}
+
+	if v.UUID == "" {
+		UUID, err := uuidFile(v.RunDir + "/uuid")
+
+		if err != nil {
+			UUID = uuid.New()
+			w, err := os.Create(v.RunDir + "/uuid")
+			if err != nil {
+				return err
+			}
+
+			defer w.Close()
+
+			if _, err := w.WriteString(UUID.String()); err != nil {
+				return err
+			}
+		}
+		v.UUID = UUID.String()
+	}
+	return nil
 }
 
 func (v *VMConfig) updateRelativePaths(configDir string, name string) {

internal/root/root.go

@@ -107,7 +107,9 @@ func Run() error {
 		return err
 	}
 
-	config.Defaults()
+	if err := config.Defaults(); err != nil {
+		return err
+	}
 	config.UpdateRelativePaths()
 
 	if debug {