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// Copyright (c) Contributors to the Apptainer project, established as
// Apptainer a Series of LF Projects LLC.
// For website terms of use, trademark policy, privacy policy and other
// project policies see https://lfprojects.org/policies
// Copyright (c) 2019, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.
package tools
import (
"fmt"
"os"
"path/filepath"
"syscall"
)
// CreateOverlay creates a writable overlay
func CreateOverlay(bundlePath string) error {
var err error
oldumask := syscall.Umask(0)
defer syscall.Umask(oldumask)
overlayDir := filepath.Join(bundlePath, "overlay")
if err = os.Mkdir(overlayDir, 0o700); err != nil {
return fmt.Errorf("failed to create %s: %s", overlayDir, err)
}
// delete overlay directory in case of error
defer func() {
if err != nil {
os.RemoveAll(overlayDir)
}
}()
err = syscall.Mount(overlayDir, overlayDir, "", syscall.MS_BIND, "")
if err != nil {
return fmt.Errorf("failed to bind %s: %s", overlayDir, err)
}
// best effort to cleanup mount
defer func() {
if err != nil {
syscall.Unmount(overlayDir, syscall.MNT_DETACH)
}
}()
if err = syscall.Mount("", overlayDir, "", syscall.MS_REMOUNT|syscall.MS_BIND, ""); err != nil {
return fmt.Errorf("failed to remount %s: %s", overlayDir, err)
}
upperDir := filepath.Join(overlayDir, "upper")
if err = os.Mkdir(upperDir, 0o755); err != nil {
return fmt.Errorf("failed to create %s: %s", upperDir, err)
}
workDir := filepath.Join(overlayDir, "work")
if err = os.Mkdir(workDir, 0o700); err != nil {
return fmt.Errorf("failed to create %s: %s", workDir, err)
}
rootFsDir := RootFs(bundlePath).Path()
options := fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", rootFsDir, upperDir, workDir)
if err = syscall.Mount("overlay", rootFsDir, "overlay", 0, options); err != nil {
return fmt.Errorf("failed to mount %s: %s", overlayDir, err)
}
return nil
}
// DeleteOverlay deletes overlay
func DeleteOverlay(bundlePath string) error {
overlayDir := filepath.Join(bundlePath, "overlay")
rootFsDir := RootFs(bundlePath).Path()
if err := syscall.Unmount(rootFsDir, syscall.MNT_DETACH); err != nil {
return fmt.Errorf("failed to unmount %s: %s", rootFsDir, err)
}
if err := syscall.Unmount(overlayDir, syscall.MNT_DETACH); err != nil {
return fmt.Errorf("failed to unmount %s: %s", overlayDir, err)
}
if err := os.RemoveAll(overlayDir); err != nil {
return fmt.Errorf("failed to remove %s: %s", overlayDir, err)
}
return nil
}
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