Add mount command

The mount command mounts the system and is meant to run in an initrd to
actually mount the root filesystem and use systemd to switch-root into
it.

It also optionally writes an /etc/fstab file to the newly mounted
system so that systemd will mount the system after switching root.

The command is used in the new dracut module elemental-rootfs, which
will coexist with immutable-rootfs (they are functionally the same)
until immutable-rootfs can be deprecated.

Signed-off-by: Fredrik Lönnegren <fredrik.lonnegren@suse.com>

cmd/config/config.go

@@ -253,6 +253,24 @@ func ReadInitSpec(r *v1.RunConfig, flags *pflag.FlagSet) (*v1.InitSpec, error) {
 	return init, err
 }
 
+func ReadMountSpec(r *v1.RunConfig, flags *pflag.FlagSet) (*v1.MountSpec, error) {
+	mount := config.NewMountSpec()
+	vp := viper.Sub("mount")
+	if vp == nil {
+		vp = viper.New()
+	}
+	// Bind install cmd flags
+	bindGivenFlags(vp, flags)
+	// Bind install env vars
+	viperReadEnv(vp, "MOUNT", constants.GetInitKeyEnvMap())
+
+	err := vp.Unmarshal(mount, setDecoder, decodeHook)
+	if err != nil {
+		r.Logger.Warnf("error unmarshalling MountSpec: %s", err)
+	}
+	return mount, err
+}
+
 func ReadResetSpec(r *v1.RunConfig, flags *pflag.FlagSet) (*v1.ResetSpec, error) {
 	reset, err := config.NewResetSpec(r.Config)
 	if err != nil {

cmd/mount.go

@@ -0,0 +1,59 @@
+/*
+Copyright © 2022 - 2023 SUSE LLC
+
+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 cmd
+
+import (
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+	"k8s.io/mount-utils"
+
+	"github.com/rancher/elemental-toolkit/cmd/config"
+	"github.com/rancher/elemental-toolkit/pkg/action"
+	"github.com/rancher/elemental-toolkit/pkg/constants"
+	elementalError "github.com/rancher/elemental-toolkit/pkg/error"
+)
+
+func MountCmd(root *cobra.Command) *cobra.Command {
+	c := &cobra.Command{
+		Use:   "mount DEVICE SYSROOT",
+		Short: "Mount an elemental system from a device into the specified sysroot",
+		Args:  cobra.MaximumNArgs(2),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			mounter := mount.New(constants.MountBinary)
+
+			cfg, err := config.ReadConfigRun(viper.GetString("config-dir"), cmd.Flags(), mounter)
+			if err != nil {
+				cfg.Logger.Errorf("Error reading config: %s\n", err)
+				return elementalError.NewFromError(err, elementalError.ReadingRunConfig)
+			}
+
+			cmd.SilenceUsage = true
+			spec, err := config.ReadMountSpec(cfg, cmd.Flags())
+			if err != nil {
+				cfg.Logger.Errorf("Error reading spec: %s\n", err)
+				return elementalError.NewFromError(err, elementalError.ReadingSpecConfig)
+			}
+
+			cfg.Logger.Infof("Mounting system...")
+			return action.RunMount(cfg, spec)
+		},
+	}
+	root.AddCommand(c)
+	return c
+}
+
+var _ = MountCmd(rootCmd)

config.yaml.example

@@ -124,6 +124,27 @@ upgrade:
   # grub menu entry, this is the string that will be displayed
   grub-entry-name: Elemental
 
+# configuration used for the 'mount' command
+mount:
+  read-kernel-cmdline: true # read and parse /proc/cmdline for arguments
+  sysroot: /sysroot
+  write-fstab: true
+  write-sentinel: true
+  rw-paths:
+    - /var
+    - /etc
+    - /srv
+  persistent:
+    mode: overlay # overlay|bind
+    paths:
+      - /etc/systemd
+      - /etc/ssh
+      - /home
+      - /opt
+      - /root
+      - /usr/libexec
+      - /var/log
+
 # use cosign to validate images from container registries
 cosign: true
 # cosign key to used for validation

pkg/action/mount.go

@@ -0,0 +1,132 @@
+/*
+Copyright © 2022 - 2023 SUSE LLC
+
+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 action
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+
+	"github.com/rancher/elemental-toolkit/pkg/constants"
+	"github.com/rancher/elemental-toolkit/pkg/elemental"
+	v1 "github.com/rancher/elemental-toolkit/pkg/types/v1"
+	"github.com/rancher/elemental-toolkit/pkg/utils"
+)
+
+func RunMount(cfg *v1.RunConfig, spec *v1.MountSpec) error {
+	cfg.Logger.Info("Running mount command")
+
+	e := elemental.NewElemental(&cfg.Config)
+
+	err := e.MountPartitions(spec.Partitions.PartitionsByMountPoint(false))
+	if err != nil {
+		return err
+	}
+
+	if err := e.MountImage(spec.Image); err != nil {
+		cfg.Logger.Errorf("Error mounting image %s: %s", spec.Image.File, err.Error())
+		return err
+	}
+
+	for _, path := range spec.RwPaths {
+		cfg.Logger.Debugf("Mounting path %s into %s", path, spec.Sysroot)
+		if err := MountRwPath(cfg, spec.Sysroot, path); err != nil {
+			cfg.Logger.Errorf("Error mounting path %s: %s", path, err.Error())
+			return err
+		}
+	}
+
+	if err := WriteFstab(cfg, spec); err != nil {
+		cfg.Logger.Errorf("Error writing new fstab: %s", err.Error())
+		return err
+	}
+
+	cfg.Logger.Info("Mount command finished successfully")
+	return nil
+}
+
+func MountRwPath(cfg *v1.RunConfig, sysroot, path string) error {
+	cfg.Logger.Debugf("Mounting Path")
+
+	lower := filepath.Join(sysroot, path)
+	if err := utils.MkdirAll(cfg.Config.Fs, lower, constants.DirPerm); err != nil {
+		cfg.Logger.Errorf("Error creating directory %s: %s", path, err.Error())
+		return err
+	}
+
+	trimmed := strings.TrimPrefix(path, "/")
+	pathName := strings.ReplaceAll(trimmed, "/", "-")
+	upper := fmt.Sprintf("%s/%s/upper", constants.OverlayDir, pathName)
+	if err := utils.MkdirAll(cfg.Config.Fs, upper, constants.DirPerm); err != nil {
+		cfg.Logger.Errorf("Error creating upperdir %s: %s", upper, err.Error())
+		return err
+	}
+
+	work := fmt.Sprintf("%s/%s/work", constants.OverlayDir, pathName)
+	if err := utils.MkdirAll(cfg.Config.Fs, work, constants.DirPerm); err != nil {
+		cfg.Logger.Errorf("Error creating workdir %s: %s", work, err.Error())
+		return err
+	}
+
+	cfg.Logger.Debugf("Mounting overlay %s", lower)
+	options := []string{"defaults"}
+	options = append(options, fmt.Sprintf("lowerdir=%s", lower))
+	options = append(options, fmt.Sprintf("upperdir=%s", upper))
+	options = append(options, fmt.Sprintf("workdir=%s", work))
+
+	if err := cfg.Mounter.Mount("overlay", lower, "overlay", options); err != nil {
+		cfg.Logger.Errorf("Error mounting overlay: %s", err.Error())
+		return err
+	}
+
+	return nil
+}
+
+// /dev/loop0 / auto ro 0 0
+// overlay /etc overlay defaults,lowerdir=/etc,upperdir=/run/elemental/overlay/etc.overlay/upper,workdir=/run/elemental/overlay/etc.overlay/work,x-systemd.requires-mounts-for=/run/elemental/overlay
+// /dev/disk/by-label/COS_OEM /oem auto defaults 0 0
+// overlay /srv overlay defaults,lowerdir=/srv,upperdir=/run/elemental/overlay/srv.overlay/upper,workdir=/run/elemental/overlay/srv.overlay/work,x-systemd.requires-mounts-for=/run/elemental/overlay
+// /dev/disk/by-label/COS_PERSISTENT /run/elemental/persistent auto defaults 0 0
+// overlay /var overlay defaults,lowerdir=/var,upperdir=/run/elemental/overlay/var.overlay/upper,workdir=/run/elemental/overlay/var.overlay/work,x-systemd.requires-mounts-for=/run/elemental/overlay
+func WriteFstab(cfg *v1.RunConfig, spec *v1.MountSpec) error {
+	if !spec.WriteFstab {
+		cfg.Logger.Debug("Skipping writing fstab")
+		return nil
+	}
+
+	data := fmt.Sprintf("%s\t/\tauto\tro\t0 0\n", spec.Image.LoopDevice)
+
+	for _, part := range spec.Partitions.PartitionsByMountPoint(false) {
+		data = data + fmt.Sprintf("%s\t%s\t%s\t%s\n", part.Path, part.MountPoint, part.FS, "")
+	}
+
+	for _, rw := range spec.RwPaths {
+		trimmed := strings.TrimPrefix(rw, "/")
+		pathName := strings.ReplaceAll(trimmed, "/", "-")
+		upper := fmt.Sprintf("%s/%s/upper", constants.OverlayDir, pathName)
+		work := fmt.Sprintf("%s/%s/work", constants.OverlayDir, pathName)
+
+		options := []string{"defaults"}
+		options = append(options, fmt.Sprintf("lowerdir=%s", rw))
+		options = append(options, fmt.Sprintf("upperdir=%s", upper))
+		options = append(options, fmt.Sprintf("workdir=%s", work))
+		options = append(options, fmt.Sprintf("x-systemd.requires-mounts-for=%s", constants.OverlayDir))
+		data = data + fmt.Sprintf("%s\t%s\t%s\t%s\n", "overlay", rw, "overlay", strings.Join(options, ","))
+	}
+
+	return cfg.Config.Fs.WriteFile(filepath.Join(spec.Sysroot, "/etc/fstab"), []byte(data), 0644)
+}

pkg/action/mount_test.go

@@ -0,0 +1,71 @@
+package action_test
+
+import (
+	"bytes"
+	"path/filepath"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	"github.com/sirupsen/logrus"
+	"github.com/twpayne/go-vfs"
+	"github.com/twpayne/go-vfs/vfst"
+	"k8s.io/mount-utils"
+
+	"github.com/rancher/elemental-toolkit/pkg/action"
+	"github.com/rancher/elemental-toolkit/pkg/config"
+	"github.com/rancher/elemental-toolkit/pkg/constants"
+	v1 "github.com/rancher/elemental-toolkit/pkg/types/v1"
+	"github.com/rancher/elemental-toolkit/pkg/utils"
+)
+
+var _ = Describe("Mount Action", func() {
+	var cfg *v1.RunConfig
+	var mounter *mount.FakeMounter
+	var fs vfs.FS
+	var logger v1.Logger
+	var cleanup func()
+	var memLog *bytes.Buffer
+
+	BeforeEach(func() {
+		mounter = &mount.FakeMounter{}
+		memLog = &bytes.Buffer{}
+		logger = v1.NewBufferLogger(memLog)
+		logger.SetLevel(logrus.DebugLevel)
+		fs, cleanup, _ = vfst.NewTestFS(map[string]interface{}{})
+		cfg = config.NewRunConfig(
+			config.WithFs(fs),
+			config.WithMounter(mounter),
+			config.WithLogger(logger),
+		)
+	})
+	AfterEach(func() {
+		cleanup()
+	})
+	Describe("Write fstab", Label("mount", "fstab"), func() {
+		It("Writes a simple fstab", func() {
+			spec := &v1.MountSpec{
+				WriteFstab: true,
+				Image: &v1.Image{
+					LoopDevice: "/dev/loop0",
+				},
+			}
+			utils.MkdirAll(fs, filepath.Join(spec.Sysroot, "/etc"), constants.DirPerm)
+			err := action.WriteFstab(cfg, spec)
+			Expect(err).To(BeNil())
+
+			fstab, err := cfg.Config.Fs.ReadFile(filepath.Join(spec.Sysroot, "/etc/fstab"))
+			Expect(err).To(BeNil())
+			Expect(string(fstab)).To(Equal("/dev/loop0\t/\tauto\tro\t0 0\n"))
+		})
+	})
+	// Describe("Mount image", Label("mount", "image"), func() {
+	// 	It("Mounts an image", func() {
+	// 		spec := &v1.MountSpec{
+	// 			Image: &v1.Image{},
+	// 		}
+
+	// 		err := action.RunMount(cfg, spec)
+	// 		Expect(err).To(BeNil())
+	// 	})
+	// })
+})

pkg/config/config.go

@@ -222,6 +222,48 @@ func NewInitSpec() *v1.InitSpec {
 	}
 }
 
+func NewMountSpec() *v1.MountSpec {
+	return &v1.MountSpec{
+		Sysroot:       "/sysroot",
+		WriteFstab:    true,
+		WriteSentinel: true,
+		Image: &v1.Image{
+			Label:      constants.ActiveLabel,
+			FS:         constants.LinuxImgFs,
+			File:       filepath.Join(constants.RunningStateDir, "cOS", constants.ActiveImgFile),
+			Source:     v1.NewFileSrc(filepath.Join(constants.RunningStateDir, "cOS", constants.ActiveImgFile)),
+			MountPoint: "/sysroot",
+		},
+		Partitions: v1.ElementalPartitions{
+			State: &v1.Partition{
+				FilesystemLabel: constants.StateLabel,
+				Size:            constants.StateSize,
+				Name:            constants.StatePartName,
+				FS:              constants.LinuxFs,
+				MountPoint:      constants.RunningStateDir,
+				Flags:           []string{},
+			},
+			Persistent: &v1.Partition{
+				FilesystemLabel: constants.PersistentLabel,
+				Size:            constants.PersistentSize,
+				Name:            constants.PersistentPartName,
+				FS:              constants.LinuxFs,
+				MountPoint:      constants.PersistentDir,
+				Flags:           []string{},
+			},
+			OEM: &v1.Partition{
+				FilesystemLabel: constants.OEMLabel,
+				Size:            constants.OEMSize,
+				Name:            constants.OEMPartName,
+				FS:              constants.LinuxFs,
+				MountPoint:      constants.OEMPath,
+				Flags:           []string{},
+			},
+		},
+		RwPaths: []string{"/var", "/etc", "/srv"},
+	}
+}
+
 func NewInstallElementalPartitions() v1.ElementalPartitions {
 	partitions := v1.ElementalPartitions{}
 	partitions.OEM = &v1.Partition{