build and convert implementations

centos: WIP

Signed-off-by: Adphi <philippe.adrien.nousse@gmail.com>

os_release.go

@@ -0,0 +1,116 @@
+// Copyright 2022 Linka Cloud  All rights reserved.
+//
+// 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 docker2vm
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"text/template"
+
+	"github.com/joho/godotenv"
+	"github.com/sirupsen/logrus"
+
+	"go.linka.cloud/d2vm/pkg/docker"
+)
+
+const (
+	ReleaseUbuntu Release = "ubuntu"
+	ReleaseDebian Release = "debian"
+	ReleaseAlpine Release = "alpine"
+	ReleaseCentOS Release = "centos"
+)
+
+type Release string
+
+func (r Release) Supported() bool {
+	switch r {
+	case ReleaseUbuntu:
+		return true
+	case ReleaseDebian:
+		return true
+	case ReleaseAlpine:
+		return true
+	case ReleaseCentOS:
+		return true
+	default:
+		return false
+	}
+}
+
+type OSRelease struct {
+	ID              Release
+	Name            string
+	VersionID       string
+	Version         string
+	VersionCodeName string
+}
+
+func ParseOSRelease(s string) (OSRelease, error) {
+	env, err := godotenv.Parse(strings.NewReader(s))
+	if err != nil {
+		return OSRelease{}, err
+	}
+	o := OSRelease{
+		ID:              Release(strings.ToLower(env["ID"])),
+		Name:            env["NAME"],
+		Version:         env["VERSION"],
+		VersionID:       env["VERSION_ID"],
+		VersionCodeName: env["VERSION_CODENAME"],
+	}
+	return o, nil
+}
+
+const (
+	osReleaseDockerfile = `
+FROM {{ . }}
+
+ENTRYPOINT [""]
+
+CMD ["/bin/cat", "/etc/os-release"]
+`
+)
+
+var (
+	osReleaseDockerfileTemplate = template.Must(template.New("osrelease.Dockerfile").Parse(osReleaseDockerfile))
+)
+
+func FetchDockerImageOSRelease(ctx context.Context, img string, tmpPath string) (OSRelease, error) {
+	d := filepath.Join(tmpPath, "osrelase.Dockerfile")
+	f, err := os.Create(d)
+	if err != nil {
+		return OSRelease{}, err
+	}
+	defer f.Close()
+	if err := osReleaseDockerfileTemplate.Execute(f, img); err != nil {
+		return OSRelease{}, err
+	}
+	imgTag := fmt.Sprintf("os-release-%s", img)
+	if err := docker.Cmd(ctx, "image", "build", "-t", imgTag, "-f", d, tmpPath); err != nil {
+		return OSRelease{}, err
+	}
+	defer func() {
+		if err := docker.Cmd(ctx, "image", "rm", imgTag); err != nil {
+			logrus.WithError(err).Error("failed to cleanup OSRelease Docker Image")
+		}
+	}()
+	o, _, err := docker.CmdOut(ctx, "run", "--rm", "-i", imgTag)
+	if err != nil {
+		return OSRelease{}, err
+	}
+	return ParseOSRelease(o)
+}