github.com/opencontainers/umoci@v0.4.8-0.20240508124516-656e4836fb0d/cmd/umoci/raw-unpack.go (about)

     1  /*
     2   * umoci: Umoci Modifies Open Containers' Images
     3   * Copyright (C) 2016-2020 SUSE LLC
     4   *
     5   * Licensed under the Apache License, Version 2.0 (the "License");
     6   * you may not use this file except in compliance with the License.
     7   * You may obtain a copy of the License at
     8   *
     9   *    http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   */
    17  
    18  package main
    19  
    20  import (
    21  	"context"
    22  	"fmt"
    23  
    24  	"github.com/apex/log"
    25  	ispec "github.com/opencontainers/image-spec/specs-go/v1"
    26  	"github.com/opencontainers/umoci"
    27  	"github.com/opencontainers/umoci/oci/cas/dir"
    28  	"github.com/opencontainers/umoci/oci/casext"
    29  	"github.com/opencontainers/umoci/oci/layer"
    30  	"github.com/pkg/errors"
    31  	"github.com/urfave/cli"
    32  )
    33  
    34  var rawUnpackCommand = uxRemap(cli.Command{
    35  	Name:  "unpack",
    36  	Usage: "unpacks a reference into a rootfs",
    37  	ArgsUsage: `--image <image-path>[:<tag>] <rootfs>
    38  
    39  Where "<image-path>" is the path to the OCI image, "<tag>" is the name of the
    40  tagged image to unpack (if not specified, defaults to "latest") and "<rootfs>"
    41  is the destination to unpack the image to.`,
    42  
    43  	// unpack reads manifest information.
    44  	Category: "image",
    45  
    46  	Flags: []cli.Flag{
    47  		cli.BoolFlag{
    48  			Name:  "keep-dirlinks",
    49  			Usage: "don't clobber underlying symlinks to directories",
    50  		},
    51  	},
    52  
    53  	Action: rawUnpack,
    54  
    55  	Before: func(ctx *cli.Context) error {
    56  		if ctx.NArg() != 1 {
    57  			return errors.Errorf("invalid number of positional arguments: expected <rootfs>")
    58  		}
    59  		if ctx.Args().First() == "" {
    60  			return errors.Errorf("rootfs path cannot be empty")
    61  		}
    62  		ctx.App.Metadata["rootfs"] = ctx.Args().First()
    63  		return nil
    64  	},
    65  })
    66  
    67  func rawUnpack(ctx *cli.Context) error {
    68  	imagePath := ctx.App.Metadata["--image-path"].(string)
    69  	fromName := ctx.App.Metadata["--image-tag"].(string)
    70  	rootfsPath := ctx.App.Metadata["rootfs"].(string)
    71  
    72  	var unpackOptions layer.UnpackOptions
    73  	var meta umoci.Meta
    74  	meta.Version = umoci.MetaVersion
    75  
    76  	// Parse map options.
    77  	// We need to set mappings if we're in rootless mode.
    78  	err := umoci.ParseIdmapOptions(&meta, ctx)
    79  	if err != nil {
    80  		return err
    81  	}
    82  
    83  	unpackOptions.KeepDirlinks = ctx.Bool("keep-dirlinks")
    84  	unpackOptions.MapOptions = meta.MapOptions
    85  
    86  	// Get a reference to the CAS.
    87  	engine, err := dir.Open(imagePath)
    88  	if err != nil {
    89  		return errors.Wrap(err, "open CAS")
    90  	}
    91  	engineExt := casext.NewEngine(engine)
    92  	defer engine.Close()
    93  
    94  	fromDescriptorPaths, err := engineExt.ResolveReference(context.Background(), fromName)
    95  	if err != nil {
    96  		return errors.Wrap(err, "get descriptor")
    97  	}
    98  	if len(fromDescriptorPaths) == 0 {
    99  		return errors.Errorf("tag is not found: %s", fromName)
   100  	}
   101  	if len(fromDescriptorPaths) != 1 {
   102  		// TODO: Handle this more nicely.
   103  		return errors.Errorf("tag is ambiguous: %s", fromName)
   104  	}
   105  	meta.From = fromDescriptorPaths[0]
   106  
   107  	manifestBlob, err := engineExt.FromDescriptor(context.Background(), meta.From.Descriptor())
   108  	if err != nil {
   109  		return errors.Wrap(err, "get manifest")
   110  	}
   111  	defer manifestBlob.Close()
   112  
   113  	if manifestBlob.Descriptor.MediaType != ispec.MediaTypeImageManifest {
   114  		return errors.Wrap(fmt.Errorf("descriptor does not point to ispec.MediaTypeImageManifest: not implemented: %s", manifestBlob.Descriptor.MediaType), "invalid --image tag")
   115  	}
   116  
   117  	log.WithFields(log.Fields{
   118  		"image":  imagePath,
   119  		"rootfs": rootfsPath,
   120  		"ref":    fromName,
   121  	}).Debugf("umoci: unpacking OCI image")
   122  
   123  	// Get the manifest.
   124  	manifest, ok := manifestBlob.Data.(ispec.Manifest)
   125  	if !ok {
   126  		// Should _never_ be reached.
   127  		return errors.Errorf("[internal error] unknown manifest blob type: %s", manifestBlob.Descriptor.MediaType)
   128  	}
   129  
   130  	log.Warnf("unpacking rootfs ...")
   131  	if err := layer.UnpackRootfs(context.Background(), engineExt, rootfsPath, manifest, &unpackOptions); err != nil {
   132  		return errors.Wrap(err, "create rootfs")
   133  	}
   134  	log.Warnf("... done")
   135  
   136  	log.Warnf("unpacked image rootfs: %s", rootfsPath)
   137  	return nil
   138  }