github.com/containerd/containerd@v22.0.0-20200918172823-438c87b8e050+incompatible/archive/tar_opts_linux.go (about)

     1  // +build linux
     2  
     3  /*
     4     Copyright The containerd Authors.
     5  
     6     Licensed under the Apache License, Version 2.0 (the "License");
     7     you may not use this file except in compliance with the License.
     8     You may obtain a copy of the License at
     9  
    10         http://www.apache.org/licenses/LICENSE-2.0
    11  
    12     Unless required by applicable law or agreed to in writing, software
    13     distributed under the License is distributed on an "AS IS" BASIS,
    14     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    15     See the License for the specific language governing permissions and
    16     limitations under the License.
    17  */
    18  
    19  package archive
    20  
    21  import (
    22  	"archive/tar"
    23  	"os"
    24  	"path/filepath"
    25  	"strings"
    26  
    27  	"golang.org/x/sys/unix"
    28  )
    29  
    30  // AufsConvertWhiteout converts whiteout files for aufs.
    31  func AufsConvertWhiteout(_ *tar.Header, _ string) (bool, error) {
    32  	return true, nil
    33  }
    34  
    35  // OverlayConvertWhiteout converts whiteout files for overlay.
    36  func OverlayConvertWhiteout(hdr *tar.Header, path string) (bool, error) {
    37  	base := filepath.Base(path)
    38  	dir := filepath.Dir(path)
    39  
    40  	// if a directory is marked as opaque, we need to translate that to overlay
    41  	if base == whiteoutOpaqueDir {
    42  		// don't write the file itself
    43  		return false, unix.Setxattr(dir, "trusted.overlay.opaque", []byte{'y'}, 0)
    44  	}
    45  
    46  	// if a file was deleted and we are using overlay, we need to create a character device
    47  	if strings.HasPrefix(base, whiteoutPrefix) {
    48  		originalBase := base[len(whiteoutPrefix):]
    49  		originalPath := filepath.Join(dir, originalBase)
    50  
    51  		if err := unix.Mknod(originalPath, unix.S_IFCHR, 0); err != nil {
    52  			return false, err
    53  		}
    54  		// don't write the file itself
    55  		return false, os.Chown(originalPath, hdr.Uid, hdr.Gid)
    56  	}
    57  
    58  	return true, nil
    59  }