containerd/rootfs/init.go

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package rootfs
import (
"context"
"fmt"
"io/ioutil"
"os"
"github.com/containerd/containerd"
"github.com/containerd/containerd/log"
"github.com/containerd/containerd/snapshot"
digest "github.com/opencontainers/go-digest"
"github.com/pkg/errors"
)
var (
initializers = map[string]initializerFunc{}
)
type initializerFunc func(string) error
func InitRootFS(ctx context.Context, name string, parent digest.Digest, readonly bool, snapshotter snapshot.Snapshotter, mounter Mounter) ([]containerd.Mount, error) {
_, err := snapshotter.Stat(ctx, name)
if err == nil {
return nil, errors.Errorf("rootfs already exists")
}
// TODO: ensure not exist error once added to snapshot package
parentS := parent.String()
initName := defaultInitializer
initFn := initializers[initName]
if initFn != nil {
parentS, err = createInitLayer(ctx, parentS, initName, initFn, snapshotter, mounter)
if err != nil {
return nil, err
}
}
if readonly {
return snapshotter.View(ctx, name, parentS)
}
return snapshotter.Prepare(ctx, name, parentS)
}
func createInitLayer(ctx context.Context, parent, initName string, initFn func(string) error, snapshotter snapshot.Snapshotter, mounter Mounter) (string, error) {
initS := fmt.Sprintf("%s %s", parent, initName)
if _, err := snapshotter.Stat(ctx, initS); err == nil {
return initS, nil
}
// TODO: ensure not exist error once added to snapshot package
// Create tempdir
td, err := ioutil.TempDir("", "create-init-")
if err != nil {
return "", err
}
defer os.RemoveAll(td)
mounts, err := snapshotter.Prepare(ctx, td, parent)
if err != nil {
return "", err
}
defer func() {
if err != nil {
// TODO: once implemented uncomment
//if rerr := snapshotter.Remove(ctx, td); rerr != nil {
// log.G(ctx).Errorf("Failed to remove snapshot %s: %v", td, merr)
//}
}
}()
if err = mounter.Mount(td, mounts...); err != nil {
return "", err
}
if err = initFn(td); err != nil {
if merr := mounter.Unmount(td); merr != nil {
log.G(ctx).Errorf("Failed to unmount %s: %v", td, merr)
}
return "", err
}
if err = mounter.Unmount(td); err != nil {
return "", err
}
if err := snapshotter.Commit(ctx, initS, td); err != nil {
return "", err
}
return initS, nil
}