github.com/ojongerius/docker@v1.11.2/pkg/chrootarchive/diff_unix.go (about)

     1  //+build !windows
     2  
     3  package chrootarchive
     4  
     5  import (
     6  	"bytes"
     7  	"encoding/json"
     8  	"flag"
     9  	"fmt"
    10  	"io/ioutil"
    11  	"os"
    12  	"path/filepath"
    13  	"runtime"
    14  
    15  	"github.com/docker/docker/pkg/archive"
    16  	"github.com/docker/docker/pkg/reexec"
    17  	"github.com/docker/docker/pkg/system"
    18  )
    19  
    20  type applyLayerResponse struct {
    21  	LayerSize int64 `json:"layerSize"`
    22  }
    23  
    24  // applyLayer is the entry-point for docker-applylayer on re-exec. This is not
    25  // used on Windows as it does not support chroot, hence no point sandboxing
    26  // through chroot and rexec.
    27  func applyLayer() {
    28  
    29  	var (
    30  		tmpDir  = ""
    31  		err     error
    32  		options *archive.TarOptions
    33  	)
    34  	runtime.LockOSThread()
    35  	flag.Parse()
    36  
    37  	if err := chroot(flag.Arg(0)); err != nil {
    38  		fatal(err)
    39  	}
    40  
    41  	// We need to be able to set any perms
    42  	oldmask, err := system.Umask(0)
    43  	defer system.Umask(oldmask)
    44  	if err != nil {
    45  		fatal(err)
    46  	}
    47  
    48  	if err := json.Unmarshal([]byte(os.Getenv("OPT")), &options); err != nil {
    49  		fatal(err)
    50  	}
    51  
    52  	if tmpDir, err = ioutil.TempDir("/", "temp-docker-extract"); err != nil {
    53  		fatal(err)
    54  	}
    55  
    56  	os.Setenv("TMPDIR", tmpDir)
    57  	size, err := archive.UnpackLayer("/", os.Stdin, options)
    58  	os.RemoveAll(tmpDir)
    59  	if err != nil {
    60  		fatal(err)
    61  	}
    62  
    63  	encoder := json.NewEncoder(os.Stdout)
    64  	if err := encoder.Encode(applyLayerResponse{size}); err != nil {
    65  		fatal(fmt.Errorf("unable to encode layerSize JSON: %s", err))
    66  	}
    67  
    68  	if _, err := flush(os.Stdin); err != nil {
    69  		fatal(err)
    70  	}
    71  
    72  	os.Exit(0)
    73  }
    74  
    75  // applyLayerHandler parses a diff in the standard layer format from `layer`, and
    76  // applies it to the directory `dest`. Returns the size in bytes of the
    77  // contents of the layer.
    78  func applyLayerHandler(dest string, layer archive.Reader, options *archive.TarOptions, decompress bool) (size int64, err error) {
    79  	dest = filepath.Clean(dest)
    80  	if decompress {
    81  		decompressed, err := archive.DecompressStream(layer)
    82  		if err != nil {
    83  			return 0, err
    84  		}
    85  		defer decompressed.Close()
    86  
    87  		layer = decompressed
    88  	}
    89  	if options == nil {
    90  		options = &archive.TarOptions{}
    91  	}
    92  	if options.ExcludePatterns == nil {
    93  		options.ExcludePatterns = []string{}
    94  	}
    95  
    96  	data, err := json.Marshal(options)
    97  	if err != nil {
    98  		return 0, fmt.Errorf("ApplyLayer json encode: %v", err)
    99  	}
   100  
   101  	cmd := reexec.Command("docker-applyLayer", dest)
   102  	cmd.Stdin = layer
   103  	cmd.Env = append(cmd.Env, fmt.Sprintf("OPT=%s", data))
   104  
   105  	outBuf, errBuf := new(bytes.Buffer), new(bytes.Buffer)
   106  	cmd.Stdout, cmd.Stderr = outBuf, errBuf
   107  
   108  	if err = cmd.Run(); err != nil {
   109  		return 0, fmt.Errorf("ApplyLayer %s stdout: %s stderr: %s", err, outBuf, errBuf)
   110  	}
   111  
   112  	// Stdout should be a valid JSON struct representing an applyLayerResponse.
   113  	response := applyLayerResponse{}
   114  	decoder := json.NewDecoder(outBuf)
   115  	if err = decoder.Decode(&response); err != nil {
   116  		return 0, fmt.Errorf("unable to decode ApplyLayer JSON response: %s", err)
   117  	}
   118  
   119  	return response.LayerSize, nil
   120  }