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Use the runtime config to specify how overlay should be created

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This puts the build side in charge of the runtime layout, which enables
additional optimisations later, like sharing the rootfs if it is
used multiple times.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>
This commit is contained in:
Justin Cormack 2017-08-22 16:21:56 +01:00
parent ee0901762f
commit 6b98aff58b
2 changed files with 35 additions and 25 deletions
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6
src/moby/build.go
View File

@ -131,13 +131,9 @@ func outputImage(image Image, section string, prefix string, m Moby, idMap map[s
if err != nil {
return fmt.Errorf("Failed to create config for %s: %v", image.Image, err)
}
runtimeConfig, err := json.MarshalIndent(runtime, "", " ")
if err != nil {
return fmt.Errorf("Failed to create runtime config for %s: %v", image.Image, err)
}
path := path.Join("containers", section, prefix+image.Name)
readonly := oci.Root.Readonly
err = ImageBundle(path, image.Image, config, runtimeConfig, iw, useTrust, pull, readonly)
err = ImageBundle(path, image.Image, config, runtime, iw, useTrust, pull, readonly)
if err != nil {
return fmt.Errorf("Failed to extract root filesystem for %s: %v", image.Image, err)
}

54
src/moby/image.go
View File

@ -3,6 +3,7 @@ package moby
import (
"archive/tar"
"bytes"
"encoding/json"
"fmt"
"io"
"io/ioutil"
@ -10,6 +11,7 @@ import (
"strings"
log "github.com/Sirupsen/logrus"
"github.com/opencontainers/runtime-spec/specs-go"
)
type tarWriter interface {
@ -189,9 +191,7 @@ func ImageTar(image, prefix string, tw tarWriter, trust bool, pull bool, resolv
}
// ImageBundle produces an OCI bundle at the given path in a tarball, given an image and a config.json
func ImageBundle(prefix string, image string, config []byte, runtimeConfig []byte, tw tarWriter, trust bool, pull bool, readonly bool) error {
log.Debugf("image bundle: %s %s cfg: %s runtime: %s", prefix, image, string(config), string(runtimeConfig))
func ImageBundle(prefix string, image string, config []byte, runtime Runtime, tw tarWriter, trust bool, pull bool, readonly bool) error {
// if read only, just unpack in rootfs/ but otherwise set up for overlay
rootfs := "rootfs"
if !readonly {
@ -214,26 +214,11 @@ func ImageBundle(prefix string, image string, config []byte, runtimeConfig []byt
return err
}
// do not write an empty runtime config
if string(runtimeConfig) != "{}" {
hdr = &tar.Header{
Name: path.Join(prefix, "runtime.json"),
Mode: 0644,
Size: int64(len(runtimeConfig)),
}
if err := tw.WriteHeader(hdr); err != nil {
return err
}
buf = bytes.NewBuffer(runtimeConfig)
if _, err := io.Copy(tw, buf); err != nil {
return err
}
}
if !readonly {
// add a tmp directory to be used as a mount point for tmpfs for upper, work
tmp := path.Join(prefix, "tmp")
hdr = &tar.Header{
Name: path.Join(prefix, "tmp"),
Name: tmp,
Mode: 0755,
Typeflag: tar.TypeDir,
}
@ -249,7 +234,36 @@ func ImageBundle(prefix string, image string, config []byte, runtimeConfig []byt
if err := tw.WriteHeader(hdr); err != nil {
return err
}
runtime.Mounts = append(runtime.Mounts, specs.Mount{Source: "tmpfs", Type: "tmpfs", Destination: "/" + tmp})
// remount private as nothing else should see the temporary layers
runtime.Mounts = append(runtime.Mounts, specs.Mount{Destination: "/" + tmp, Options: []string{"remount", "private"}})
overlayOptions := []string{"lowerdir=/" + path.Join(prefix, "lower"), "upperdir=/" + path.Join(tmp, "upper"), "workdir=/" + path.Join(tmp, "work")}
runtime.Mounts = append(runtime.Mounts, specs.Mount{Source: "overlay", Type: "overlay", Destination: "/" + path.Join(prefix, "rootfs"), Options: overlayOptions})
} else {
// make rootfs a mountpoint as runc can be picky about this
runtime.Mounts = append(runtime.Mounts, specs.Mount{Source: path.Join(prefix, rootfs), Destination: "/" + path.Join(prefix, "rootfs"), Options: []string{"bind"}})
}
// write the runtime config
runtimeConfig, err := json.MarshalIndent(runtime, "", " ")
if err != nil {
return fmt.Errorf("Failed to create runtime config for %s: %v", image, err)
}
hdr = &tar.Header{
Name: path.Join(prefix, "runtime.json"),
Mode: 0644,
Size: int64(len(runtimeConfig)),
}
if err := tw.WriteHeader(hdr); err != nil {
return err
}
buf = bytes.NewBuffer(runtimeConfig)
if _, err := io.Copy(tw, buf); err != nil {
return err
}
log.Debugf("image bundle: %s %s cfg: %s runtime: %s", prefix, image, string(config), string(runtimeConfig))
return nil
}