github.com/daaku/docker@v1.5.0/pkg/chrootarchive/diff.go (about)

     1  package chrootarchive
     2  
     3  import (
     4  	"bytes"
     5  	"encoding/json"
     6  	"flag"
     7  	"fmt"
     8  	"io/ioutil"
     9  	"os"
    10  	"path/filepath"
    11  	"runtime"
    12  	"syscall"
    13  
    14  	"github.com/docker/docker/pkg/archive"
    15  	"github.com/docker/docker/pkg/reexec"
    16  )
    17  
    18  type applyLayerResponse struct {
    19  	LayerSize int64 `json:"layerSize"`
    20  }
    21  
    22  func applyLayer() {
    23  	runtime.LockOSThread()
    24  	flag.Parse()
    25  
    26  	if err := chroot(flag.Arg(0)); err != nil {
    27  		fatal(err)
    28  	}
    29  
    30  	// We need to be able to set any perms
    31  	oldmask := syscall.Umask(0)
    32  	defer syscall.Umask(oldmask)
    33  	tmpDir, err := ioutil.TempDir("/", "temp-docker-extract")
    34  	if err != nil {
    35  		fatal(err)
    36  	}
    37  
    38  	os.Setenv("TMPDIR", tmpDir)
    39  	size, err := archive.UnpackLayer("/", os.Stdin)
    40  	os.RemoveAll(tmpDir)
    41  	if err != nil {
    42  		fatal(err)
    43  	}
    44  
    45  	encoder := json.NewEncoder(os.Stdout)
    46  	if err := encoder.Encode(applyLayerResponse{size}); err != nil {
    47  		fatal(fmt.Errorf("unable to encode layerSize JSON: %s", err))
    48  	}
    49  
    50  	flush(os.Stdout)
    51  	flush(os.Stdin)
    52  	os.Exit(0)
    53  }
    54  
    55  func ApplyLayer(dest string, layer archive.ArchiveReader) (size int64, err error) {
    56  	dest = filepath.Clean(dest)
    57  	decompressed, err := archive.DecompressStream(layer)
    58  	if err != nil {
    59  		return 0, err
    60  	}
    61  
    62  	defer decompressed.Close()
    63  
    64  	cmd := reexec.Command("docker-applyLayer", dest)
    65  	cmd.Stdin = decompressed
    66  
    67  	outBuf, errBuf := new(bytes.Buffer), new(bytes.Buffer)
    68  	cmd.Stdout, cmd.Stderr = outBuf, errBuf
    69  
    70  	if err = cmd.Run(); err != nil {
    71  		return 0, fmt.Errorf("ApplyLayer %s stdout: %s stderr: %s", err, outBuf, errBuf)
    72  	}
    73  
    74  	// Stdout should be a valid JSON struct representing an applyLayerResponse.
    75  	response := applyLayerResponse{}
    76  	decoder := json.NewDecoder(outBuf)
    77  	if err = decoder.Decode(&response); err != nil {
    78  		return 0, fmt.Errorf("unable to decode ApplyLayer JSON response: %s", err)
    79  	}
    80  
    81  	return response.LayerSize, nil
    82  }