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moby--moby/pkg/chrootarchive/archive.go

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package chrootarchive
import (
"encoding/json"
"flag"
"fmt"
"io"
"os"
"path/filepath"
"runtime"
"syscall"
"github.com/docker/docker/pkg/archive"
"github.com/docker/docker/pkg/reexec"
)
var chrootArchiver = &archive.Archiver{Untar: Untar}
func chroot(path string) error {
if err := syscall.Chroot(path); err != nil {
return err
}
return syscall.Chdir("/")
}
func untar() {
runtime.LockOSThread()
flag.Parse()
var options *archive.TarOptions
if err := json.Unmarshal([]byte(os.Getenv("OPT")), &options); err != nil {
fatal(err)
}
if err := chroot(flag.Arg(0)); err != nil {
fatal(err)
}
if err := archive.Unpack(os.Stdin, "/", options); err != nil {
fatal(err)
}
// fully consume stdin in case it is zero padded
flush(os.Stdin)
os.Exit(0)
}
func Untar(tarArchive io.Reader, dest string, options *archive.TarOptions) error {
if tarArchive == nil {
return fmt.Errorf("Empty archive")
}
if options == nil {
options = &archive.TarOptions{}
}
if options.ExcludePatterns == nil {
options.ExcludePatterns = []string{}
}
dest = filepath.Clean(dest)
if _, err := os.Stat(dest); os.IsNotExist(err) {
if err := os.MkdirAll(dest, 0777); err != nil {
return err
}
}
// We can't pass the exclude list directly via cmd line
// because we easily overrun the shell max argument list length
// when the full image list is passed (e.g. when this is used
// by `docker load`). Instead we will add the JSON marshalled
// and placed in the env, which has significantly larger
// max size
data, err := json.Marshal(options)
if err != nil {
return fmt.Errorf("Untar json encode: %v", err)
}
decompressedArchive, err := archive.DecompressStream(tarArchive)
if err != nil {
return err
}
defer decompressedArchive.Close()
cmd := reexec.Command("docker-untar", dest)
cmd.Stdin = decompressedArchive
cmd.Env = append(cmd.Env, fmt.Sprintf("OPT=%s", data))
out, err := cmd.CombinedOutput()
if err != nil {
return fmt.Errorf("Untar %s %s", err, out)
}
return nil
}
func TarUntar(src, dst string) error {
return chrootArchiver.TarUntar(src, dst)
}
// CopyWithTar creates a tar archive of filesystem path `src`, and
// unpacks it at filesystem path `dst`.
// The archive is streamed directly with fixed buffering and no
// intermediary disk IO.
func CopyWithTar(src, dst string) error {
return chrootArchiver.CopyWithTar(src, dst)
}
// CopyFileWithTar emulates the behavior of the 'cp' command-line
// for a single file. It copies a regular file from path `src` to
// path `dst`, and preserves all its metadata.
//
// If `dst` ends with a trailing slash '/', the final destination path
// will be `dst/base(src)`.
func CopyFileWithTar(src, dst string) (err error) {
return chrootArchiver.CopyFileWithTar(src, dst)
}
// UntarPath is a convenience function which looks for an archive
// at filesystem path `src`, and unpacks it at `dst`.
func UntarPath(src, dst string) error {
return chrootArchiver.UntarPath(src, dst)
}