Function doTmpfsCopyUp

libcontainer/rootfs_linux.go:436–492

(m mountEntry, mountLabel string)

}

func doTmpfsCopyUp(m mountEntry, mountLabel string) (Err error) {
	// Set up a scratch dir for the tmpfs on the host.
	tmpdir, err := prepareTmp("/tmp")
	if err != nil {
		return fmt.Errorf("tmpcopyup: failed to setup tmpdir: %w", err)
	}
	defer cleanupTmp(tmpdir)
	tmpDir, err := os.MkdirTemp(tmpdir, "runctmpdir")
	if err != nil {
		return fmt.Errorf("tmpcopyup: failed to create tmpdir: %w", err)
	}
	defer os.RemoveAll(tmpDir)

	tmpDirFile, err := os.OpenFile(tmpDir, unix.O_DIRECTORY|unix.O_CLOEXEC, 0)
	if err != nil {
		return fmt.Errorf("tmpcopyup: %w", err)
	}
	defer tmpDirFile.Close()

	hostRootFd, err := os.OpenFile("/", unix.O_DIRECTORY|unix.O_CLOEXEC|unix.O_PATH, 0)
	if err != nil {
		return fmt.Errorf("tmpcopyup: open host root: %w", err)
	}
	defer hostRootFd.Close()

	// Configure the *host* tmpdir as if it's the container mount. We change
	// m.dstFile since we are going to mount *on the host*.
	hostMount := mountEntry{
		Mount:   m.Mount,
		dstFile: tmpDirFile,
	}
	if err := hostMount.mountPropagate(hostRootFd, mountLabel); err != nil {
		return err
	}
	hostRootFd.Close()
	defer func() {
		if Err != nil {
			if err := unmount(tmpDir, unix.MNT_DETACH); err != nil {
				logrus.Warnf("tmpcopyup: %v", err)
			}
		}
	}()

	return utils.WithProcfdFile(m.dstFile, func(dstFd string) (Err error) {
		// Copy the container data to the host tmpdir. We append "/" to force
		// CopyDirectory to resolve the symlink rather than trying to copy the
		// symlink itself.
		if err := fileutils.CopyDirectory(dstFd+"/", tmpDir); err != nil {
			return fmt.Errorf("tmpcopyup: failed to copy %s to %s (%s): %w", m.Destination, dstFd, tmpDir, err)
		}
		// Now move the mount into the container.
		if err := mountViaFds(tmpDir, nil, m.Destination, dstFd, "", unix.MS_MOVE, ""); err != nil {
			return fmt.Errorf("tmpcopyup: failed to move mount: %w", err)
		}
		return nil
	})
}