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package daemon // import "github.com/docker/docker/daemon"
import (
"os"
"path/filepath"
"github.com/docker/docker/pkg/ioutils"
"github.com/google/uuid"
"github.com/pkg/errors"
)
const idFilename = "engine-id"
// LoadOrCreateID loads the engine's ID from the given root, or generates a new ID
// if it doesn't exist. It returns the ID, and any error that occurred when
// saving the file.
//
// Note that this function expects the daemon's root directory to already have
// been created with the right permissions and ownership (usually this would
// be done by daemon.CreateDaemonRoot().
func LoadOrCreateID(root string) (string, error) {
var id string
idPath := filepath.Join(root, idFilename)
idb, err := os.ReadFile(idPath)
if os.IsNotExist(err) {
id = uuid.New().String()
if err := ioutils.AtomicWriteFile(idPath, []byte(id), os.FileMode(0o600)); err != nil {
return "", errors.Wrap(err, "error saving ID file")
}
} else if err != nil {
return "", errors.Wrapf(err, "error loading ID file %s", idPath)
} else {
id = string(idb)
}
return id, nil
}
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