Code maintenance: OS package for file system

- OS custom internal package for file system interaction
- Remove fileManager external dependency
- Closer API to Go's native API on the OS
- Create directories at startup
- Better testability
- Move Unsetenv to os interface

internal/alpine/alpine.go

@@ -3,7 +3,7 @@ package alpine
 import (
 	"os/user"
 
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 )
 
 type Configurator interface {
@@ -11,15 +11,15 @@ type Configurator interface {
 }
 
 type configurator struct {
-	fileManager files.FileManager
-	lookupUID   func(uid string) (*user.User, error)
-	lookupUser  func(username string) (*user.User, error)
+	openFile   os.OpenFileFunc
+	lookupUID  func(uid string) (*user.User, error)
+	lookupUser func(username string) (*user.User, error)
 }
 
-func NewConfigurator(fileManager files.FileManager) Configurator {
+func NewConfigurator(openFile os.OpenFileFunc) Configurator {
 	return &configurator{
-		fileManager: fileManager,
-		lookupUID:   user.LookupId,
-		lookupUser:  user.Lookup,
+		openFile:   openFile,
+		lookupUID:  user.LookupId,
+		lookupUser: user.Lookup,
 	}
 }

internal/alpine/users.go

@@ -2,6 +2,7 @@ package alpine
 
 import (
 	"fmt"
+	"os"
 	"os/user"
 )
 
@@ -26,14 +27,15 @@ func (c *configurator) CreateUser(username string, uid int) (createdUsername str
 		return "", fmt.Errorf("cannot create user: user with name %s already exists for ID %s instead of %d",
 			username, u.Uid, uid)
 	}
-	passwd, err := c.fileManager.ReadFile("/etc/passwd")
+	file, err := c.openFile("/etc/passwd", os.O_APPEND|os.O_WRONLY, 0644)
 	if err != nil {
 		return "", fmt.Errorf("cannot create user: %w", err)
 	}
-	passwd = append(passwd, []byte(fmt.Sprintf("%s:x:%d:::/dev/null:/sbin/nologin\n", username, uid))...)
-
-	if err := c.fileManager.WriteToFile("/etc/passwd", passwd); err != nil {
-		return "", fmt.Errorf("cannot create user: %w", err)
+	s := fmt.Sprintf("%s:x:%d:::/dev/null:/sbin/nologin\n", username, uid)
+	_, err = file.WriteString(s)
+	if err != nil {
+		_ = file.Close()
+		return "", err
 	}
-	return username, nil
+	return username, file.Close()
 }