Added basic restic command module.

This helps interact with a restic binary to get the actual backup process running.

Author: Lukas Knuth

restic/command.go

@@ -0,0 +1,70 @@
+package restic
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+// Empty string = current directory.
+const CURRENT_DIR = ""
+
+func SafeInit() (err error) {
+	err = execRestic([]string{"snapshots"}, CURRENT_DIR)
+	var e *exec.ExitError
+	if err != nil && errors.As(err, &e) {
+		if e.ExitCode() != 0 {
+			// No repo initialized yet!
+			err = execRestic([]string{"init"}, CURRENT_DIR)
+		}
+	}
+	// no error, the repo is initialized and accessible
+	return
+}
+
+func Backup(pvcName string) error {
+	workingDir := envFallback("BACKUP_TARGET_DIR", "/mnt/target")
+	err := execRestic([]string{"backup", ".", "--no-cache", "--host", pvcName}, workingDir)
+	return err
+}
+
+func Restore(pvcName string) error {
+	workingDir := envFallback("RESTORE_TARGET_DIR", "/mnt/target")
+	err := execRestic([]string{"restore", "latest", "--target", workingDir, "--no-cache", "--host", pvcName}, CURRENT_DIR)
+	return err
+}
+
+func Version() error {
+	return execRestic([]string{"version"}, CURRENT_DIR)
+}
+
+func execRestic(args []string, workingDir string) error {
+	resticPath := envFallback("RESTIC_PATH", "/app/restic")
+	command := exec.Cmd {
+		Path: resticPath,
+		Args: append([]string{resticPath}, args...),
+		Env: nil, // Re-use environment from this process!
+		Dir: workingDir,
+	}
+	var e *exec.ExitError
+	output, err := command.CombinedOutput()
+	fmt.Printf("--- Restic invocation ---\n")
+	fmt.Printf("Path: %s\nArgs: %s\n", resticPath, args)
+	if err != nil && errors.As(err, &e) {
+		fmt.Printf("Exit Code: %d", e.ExitCode())
+	} else {
+		fmt.Println("Exit Code: 0")
+	}
+	fmt.Printf("--- Output Start ---\n%s\n--- Output End ---\n", output)
+	return err
+}
+
+func envFallback(name string, fallback string) string {
+	value, found := os.LookupEnv(name)
+	if found {
+		return value
+	} else {
+		return fallback
+	}
+}