feat: docker container handles PID / GID for alpine image

cmd/docker-entrypoint/main.go

@@ -1,9 +1,14 @@
+//go:build linux
+
 package main
 
 import (
 	"fmt"
 	"os"
 	"os/exec"
+	"os/user"
+	"strconv"
+	"syscall"
 )
 
 var dockerEnvVarDefaults = map[string]string{
@@ -24,21 +29,112 @@
 			os.Stderr.WriteString(" - " + key + "\n")
 		}
 	}
+
+	// Setup user and group
+	uid, gid, err := setupUserAndGroup()
+	if err != nil {
+		os.Stderr.WriteString(fmt.Sprintf("Failed to setup user/group: %v\n", err))
+		os.Exit(1)
+	}
+
 	if len(os.Args) < 2 {
 		os.Stderr.WriteString("No command provided to run.\n")
 		os.Exit(1)
 	}
+
+	if uid != 0 {
+		os.Stderr.WriteString(fmt.Sprintf("Switching to user with UID=%d, GID=%d\n", uid, gid))
+	}
 	os.Stderr.WriteString("Running command: " + os.Args[1] + " " + fmt.Sprint(os.Args[2:]) + "\n")
 
 	cmd := exec.Command(os.Args[1], os.Args[2:]...)
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	cmd.Stdin = os.Stdin
 
+	// Set the user and group for the command if not root
+	if uid != 0 {
+		cmd.SysProcAttr = &syscall.SysProcAttr{
+			Credential: &syscall.Credential{
+				Uid: uint32(uid),
+				Gid: uint32(gid),
+			},
+		}
+	}
+
 	if err := cmd.Run(); err != nil {
 		if exitError, ok := err.(*exec.ExitError); ok {
 			os.Exit(exitError.ExitCode())
 		}
 		panic(err)
 	}
 }
+
+// setupUserAndGroup handles PUID/PGID setup
+func setupUserAndGroup() (int, int, error) {
+	puidStr := os.Getenv("PUID")
+	pgidStr := os.Getenv("PGID")
+
+	// Default to running as root if PUID is empty or 0
+	if puidStr == "" || puidStr == "0" {
+		return 0, 0, nil
+	}
+
+	puid, err := strconv.ParseUint(puidStr, 10, 32)
+	if err != nil {
+		return 0, 0, fmt.Errorf("invalid PUID: %v", err)
+	}
+
+	pgid, err := strconv.ParseUint(pgidStr, 10, 32)
+	if err != nil {
+		return 0, 0, fmt.Errorf("invalid PGID: %v", err)
+	}
+
+	username := "abc"
+	groupname := "abc"
+
+	// Check if user already exists
+	if !userExists(username) {
+		// Create group if it doesn't exist
+		if !groupExists(groupname) {
+			if err := createGroup(groupname, int(pgid)); err != nil {
+				return 0, 0, fmt.Errorf("failed to create group %s: %v", groupname, err)
+			}
+			os.Stderr.WriteString(fmt.Sprintf("Created group %s with GID %d\n", groupname, pgid))
+		}
+
+		// Create user
+		if err := createUser(username, groupname, int(puid)); err != nil {
+			return 0, 0, fmt.Errorf("failed to create user %s: %v", username, err)
+		}
+		os.Stderr.WriteString(fmt.Sprintf("Created user %s with UID %d\n", username, puid))
+	}
+
+	return puid, pgid, nil
+}
+
+// userExists checks if a user exists by name
+func userExists(username string) bool {
+	_, err := user.Lookup(username)
+	return err == nil
+}
+
+// groupExists checks if a group exists by running getent group
+func groupExists(groupname string) bool {
+	cmd := exec.Command("getent", "group", groupname)
+	return cmd.Run() == nil
+}
+
+// createGroup creates a group with the specified GID
+func createGroup(groupname string, gid int) error {
+	cmd := exec.Command("groupadd", "-g", strconv.Itoa(gid), groupname)
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+// createUser creates a user with the specified UID and group
+func createUser(username, groupname string, uid int) error {
+	cmd := exec.Command("useradd", "-m", "-u", strconv.Itoa(uid), "-g", groupname, username)
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}