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raw-unpack.go
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/
raw-unpack.go
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/*
* umoci: Umoci Modifies Open Containers' Images
* Copyright (C) 2018 SUSE LLC.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package main
import (
"fmt"
"github.com/apex/log"
"github.com/openSUSE/umoci"
"github.com/openSUSE/umoci/oci/cas/dir"
"github.com/openSUSE/umoci/oci/casext"
"github.com/openSUSE/umoci/oci/layer"
ispec "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/pkg/errors"
"github.com/urfave/cli"
"golang.org/x/net/context"
)
var rawUnpackCommand = uxRemap(cli.Command{
Name: "unpack",
Usage: "unpacks a reference into a rootfs",
ArgsUsage: `--image <image-path>[:<tag>] <rootfs>
Where "<image-path>" is the path to the OCI image, "<tag>" is the name of the
tagged image to unpack (if not specified, defaults to "latest") and "<rootfs>"
is the destination to unpack the image to.`,
// unpack reads manifest information.
Category: "image",
Flags: []cli.Flag{
cli.BoolFlag{
Name: "keep-dirlinks",
Usage: "don't clobber underlying symlinks to directories",
},
},
Action: rawUnpack,
Before: func(ctx *cli.Context) error {
if ctx.NArg() != 1 {
return errors.Errorf("invalid number of positional arguments: expected <rootfs>")
}
if ctx.Args().First() == "" {
return errors.Errorf("rootfs path cannot be empty")
}
ctx.App.Metadata["rootfs"] = ctx.Args().First()
return nil
},
})
func rawUnpack(ctx *cli.Context) error {
imagePath := ctx.App.Metadata["--image-path"].(string)
fromName := ctx.App.Metadata["--image-tag"].(string)
rootfsPath := ctx.App.Metadata["rootfs"].(string)
var meta umoci.Meta
meta.Version = umoci.MetaVersion
// Parse map options.
// We need to set mappings if we're in rootless mode.
err := umoci.ParseIdmapOptions(&meta, ctx)
if err != nil {
return err
}
meta.MapOptions.KeepDirlinks = ctx.Bool("keep-dirlinks")
// Get a reference to the CAS.
engine, err := dir.Open(imagePath)
if err != nil {
return errors.Wrap(err, "open CAS")
}
engineExt := casext.NewEngine(engine)
defer engine.Close()
fromDescriptorPaths, err := engineExt.ResolveReference(context.Background(), fromName)
if err != nil {
return errors.Wrap(err, "get descriptor")
}
if len(fromDescriptorPaths) == 0 {
return errors.Errorf("tag is not found: %s", fromName)
}
if len(fromDescriptorPaths) != 1 {
// TODO: Handle this more nicely.
return errors.Errorf("tag is ambiguous: %s", fromName)
}
meta.From = fromDescriptorPaths[0]
manifestBlob, err := engineExt.FromDescriptor(context.Background(), meta.From.Descriptor())
if err != nil {
return errors.Wrap(err, "get manifest")
}
defer manifestBlob.Close()
if manifestBlob.MediaType != ispec.MediaTypeImageManifest {
return errors.Wrap(fmt.Errorf("descriptor does not point to ispec.MediaTypeImageManifest: not implemented: %s", manifestBlob.MediaType), "invalid --image tag")
}
log.WithFields(log.Fields{
"image": imagePath,
"rootfs": rootfsPath,
"ref": fromName,
}).Debugf("umoci: unpacking OCI image")
// Get the manifest.
manifest, ok := manifestBlob.Data.(ispec.Manifest)
if !ok {
// Should _never_ be reached.
return errors.Errorf("[internal error] unknown manifest blob type: %s", manifestBlob.MediaType)
}
// FIXME: Currently we only support OCI layouts, not tar archives. This
// should be fixed once the CAS engine PR is merged into
// image-tools. https://github.com/opencontainers/image-tools/pull/5
log.Warnf("unpacking rootfs ...")
if err := layer.UnpackRootfs(context.Background(), engineExt, rootfsPath, manifest, &meta.MapOptions); err != nil {
return errors.Wrap(err, "create rootfs")
}
log.Warnf("... done")
log.Warnf("unpacked image rootfs: %s", rootfsPath)
return nil
}