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/
image_extract.go
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/
image_extract.go
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// Copyright 2015 The rkt Authors
//
// 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 (
"io/ioutil"
"os"
"path/filepath"
"syscall"
"github.com/rkt/rkt/pkg/fileutil"
"github.com/rkt/rkt/pkg/tar"
"github.com/rkt/rkt/pkg/user"
"github.com/rkt/rkt/store/imagestore"
"github.com/spf13/cobra"
)
var (
cmdImageExtract = &cobra.Command{
Use: "extract IMAGE OUTPUT_DIR",
Short: "Extract a stored image to a directory",
Long: `IMAGE should be a string referencing an image: either a ID or an image name.
Note that in order to make cleaning up easy (just rm -rf), extract does not use
overlayfs or any other mechanism.`,
Run: runWrapper(runImageExtract),
}
flagExtractRootfsOnly bool
flagExtractOverwrite bool
)
func init() {
cmdImage.AddCommand(cmdImageExtract)
cmdImageExtract.Flags().BoolVar(&flagExtractRootfsOnly, "rootfs-only", false, "extract rootfs only")
cmdImageExtract.Flags().BoolVar(&flagExtractOverwrite, "overwrite", false, "overwrite output directory")
}
func runImageExtract(cmd *cobra.Command, args []string) (exit int) {
if len(args) != 2 {
cmd.Usage()
return 254
}
outputDir := args[1]
s, err := imagestore.NewStore(storeDir())
if err != nil {
stderr.PrintE("cannot open store", err)
return 254
}
key, err := getStoreKeyFromAppOrHash(s, args[0])
if err != nil {
stderr.Error(err)
return 254
}
aci, err := s.ReadStream(key)
if err != nil {
stderr.PrintE("error reading ACI from the store", err)
return 254
}
// ExtractTar needs an absolute path
absOutputDir, err := filepath.Abs(outputDir)
if err != nil {
stderr.PrintE("error converting output to an absolute path", err)
return 254
}
if _, err := os.Stat(absOutputDir); err == nil {
if !flagExtractOverwrite {
stderr.Print("output directory exists (try --overwrite)")
return 254
}
// don't allow the user to delete the root filesystem by mistake
if absOutputDir == "/" {
stderr.Print("this would delete your root filesystem. Refusing.")
return 254
}
if err := os.RemoveAll(absOutputDir); err != nil {
stderr.PrintE("error removing existing output dir", err)
return 254
}
}
// if the user only asks for the rootfs we extract the image to a temporary
// directory and then move/copy the rootfs to the output directory, if not
// we just extract the image to the output directory
extractDir := absOutputDir
if flagExtractRootfsOnly {
rktTmpDir, err := s.TmpDir()
if err != nil {
stderr.PrintE("error creating rkt temporary directory", err)
return 254
}
tmpDir, err := ioutil.TempDir(rktTmpDir, "rkt-image-extract-")
if err != nil {
stderr.PrintE("error creating temporary directory", err)
return 254
}
defer os.RemoveAll(tmpDir)
extractDir = tmpDir
} else {
if err := os.MkdirAll(absOutputDir, 0755); err != nil {
stderr.PrintE("error creating output directory", err)
return 254
}
}
if err := tar.ExtractTar(aci, extractDir, false, user.NewBlankUidRange(), nil); err != nil {
stderr.PrintE("error extracting ACI", err)
return 254
}
if flagExtractRootfsOnly {
rootfsDir := filepath.Join(extractDir, "rootfs")
if err := os.Rename(rootfsDir, absOutputDir); err != nil {
if e, ok := err.(*os.LinkError); ok && e.Err == syscall.EXDEV {
// it's on a different device, fall back to copying
if err := fileutil.CopyTree(rootfsDir, absOutputDir, user.NewBlankUidRange()); err != nil {
stderr.PrintE("error copying ACI rootfs", err)
return 254
}
} else {
stderr.PrintE("error moving ACI rootfs", err)
return 254
}
}
}
return 0
}