adds mount-sys command

cmd/mount-sys.go

@@ -0,0 +1,274 @@
+package cmd
+
+/*	License: GPLv3
+	Authors:
+		Mirko Brombin <mirko@fabricators.ltd>
+		Vanilla OS Contributors <https://github.com/vanilla-os/>
+	Copyright: 2024
+	Description:
+		ABRoot is utility which provides full immutability and
+		atomicity to a Linux system, by transacting between
+		two root filesystems. Updates are performed using OCI
+		images, to ensure that the system is always in a
+		consistent state.
+*/
+
+import (
+	"fmt"
+	"os"
+	"slices"
+	"strings"
+	"syscall"
+
+	"github.com/spf13/cobra"
+
+	"github.com/vanilla-os/abroot/core"
+	"github.com/vanilla-os/abroot/settings"
+	"github.com/vanilla-os/orchid/cmdr"
+)
+
+type DiskLayoutError struct {
+	Device string
+}
+
+func (e *DiskLayoutError) Error() string {
+	return fmt.Sprintf("device %s has an unsupported layout", e.Device)
+}
+
+type PartNotFoundError struct {
+	Partition string
+}
+
+func (e *PartNotFoundError) Error() string {
+	return fmt.Sprintf("partition %s could not be found", e.Partition)
+}
+
+func NewMountSysCommand() *cmdr.Command {
+	cmd := cmdr.NewCommand(
+		"mount-sys",
+		"",
+		"",
+		mountSysCmd,
+	)
+
+	cmd.WithBoolFlag(
+		cmdr.NewBoolFlag(
+			"dry-run",
+			"d",
+			"perform a dry run of the operation",
+			false,
+		),
+	)
+
+	cmd.Example = "abroot mount-sys"
+
+	cmd.Hidden = true
+
+	return cmd
+}
+
+// helper function which only returns syntax errors and prints other ones
+func mountSysCmd(cmd *cobra.Command, args []string) error {
+	err := mountSys(cmd, args)
+	if err != nil {
+		cmdr.Error.Println(err)
+		os.Exit(1)
+	}
+	return nil
+}
+
+func mountSys(cmd *cobra.Command, _ []string) error {
+	if !core.RootCheck(false) {
+		cmdr.Error.Println("This operation requires root.")
+		return nil
+	}
+
+	dryRun, err := cmd.Flags().GetBool("dry-run")
+	if err != nil {
+		return err
+	}
+
+	manager := core.NewABRootManager()
+	present, err := manager.GetPresent()
+	if err != nil {
+		return err
+	}
+
+	err = mountVar(manager.VarPartition, dryRun)
+	if err != nil {
+		cmdr.Error.Println(err)
+		os.Exit(5)
+	}
+
+	err = mountBindMounts(dryRun)
+	if err != nil {
+		cmdr.Error.Println(err)
+		os.Exit(6)
+	}
+
+	if present.Label == "" {
+		return &PartNotFoundError{"current root"}
+	}
+	err = mountOverlayMounts(present.Label, dryRun)
+	if err != nil {
+		cmdr.Error.Println(err)
+		os.Exit(7)
+	}
+
+	if present.Uuid == "" {
+		return &PartNotFoundError{"current root"}
+	}
+	err = adjustFstab(present.Uuid, dryRun)
+	if err != nil {
+		cmdr.Error.Println(err)
+		os.Exit(8)
+	}
+
+	if dryRun {
+		cmdr.Info.Println("Dry run complete.")
+	} else {
+		cmdr.Info.Println("The system mounts have been performed successfully.")
+	}
+
+	return nil
+}
+
+func mountVar(varPart core.Partition, dryRun bool) error {
+	cmdr.FgDefault.Println("mounting " + varPart.Device + " in /var")
+
+	if varPart.Device == "" {
+		return &PartNotFoundError{settings.Cnf.PartLabelVar}
+	}
+
+	if !dryRun {
+		err := varPart.Mount("/var")
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func mountBindMounts(dryRun bool) error {
+	type bindMount struct {
+		from, to string
+		options  uintptr
+	}
+
+	binds := []bindMount{
+		{"/var/home", "/home", 0},
+		{"/var/opt", "/opt", 0},
+		{"/.system/usr", "/.system/usr", syscall.MS_RDONLY},
+	}
+
+	for _, bind := range binds {
+		cmdr.FgDefault.Println("bind-mounting " + bind.from + " to " + bind.to)
+		if !dryRun {
+			err := syscall.Mount(bind.from, bind.to, "", syscall.MS_BIND|bind.options, "")
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func mountOverlayMounts(rootLabel string, dryRun bool) error {
+	type overlayMount struct {
+		destination       string
+		lowerdirs         []string
+		upperdir, workdir string
+	}
+
+	overlays := []overlayMount{
+		{"/.system/etc", []string{"/.system/etc"}, "/var/lib/abroot/etc/" + rootLabel, "/var/lib/abroot/etc/" + rootLabel + "-work"},
+	}
+
+	for _, overlay := range overlays {
+		lowerCombined := strings.Join(overlay.lowerdirs, ":")
+		options := "lowerdir=" + lowerCombined + ",upperdir=" + overlay.upperdir + ",workdir=" + overlay.workdir
+
+		cmdr.FgDefault.Println("mounting overlay mount " + overlay.destination + " with options " + options)
+
+		if !dryRun {
+			err := syscall.Mount("overlay", overlay.destination, "overlay", 0, options)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func adjustFstab(uuid string, dryRun bool) error {
+	cmdr.FgDefault.Println("switching the root in fstab")
+
+	const fstabFile = "/etc/fstab"
+	systemMounts := []string{"/", "/var", "/.system/usr", "/.system/etc"}
+
+	fstabContentsRaw, err := os.ReadFile(fstabFile)
+	if err != nil {
+		return err
+	}
+
+	fstabContents := string(fstabContentsRaw)
+
+	lines := strings.Split(fstabContents, "\n")
+
+	linesNew := make([]string, 0, len(lines))
+
+	// remove system Mounts if they exist in fstab
+	for _, line := range lines {
+
+		line = strings.TrimSpace(line)
+		if strings.HasPrefix(line, "#") {
+			linesNew = append(linesNew, line)
+			continue
+		}
+
+		words := strings.Fields(line)
+		if len(words) < 2 {
+			linesNew = append(linesNew, line)
+			continue
+		}
+
+		if !slices.Contains[[]string](systemMounts, words[1]) {
+			linesNew = append(linesNew, line)
+			continue
+		}
+
+		cmdr.FgDefault.Println("Deleting line: ", line)
+	}
+
+	currentRootLine := "UUID=" + uuid + " / btrfs defaults 0 0"
+
+	cmdr.FgDefault.Println("Adding line: ", currentRootLine)
+
+	linesNew = append([]string{currentRootLine}, linesNew...)
+
+	newFstabContents := strings.Join(linesNew, "\n")
+
+	newFstabFile := fstabFile + ".new"
+
+	if !dryRun {
+		cmdr.FgDefault.Println("writing new fstab file")
+		err := os.WriteFile(newFstabFile, []byte(newFstabContents), 0o644)
+		if err != nil {
+			return err
+		}
+		err = core.AtomicSwap(fstabFile, newFstabFile)
+		if err != nil {
+			return err
+		}
+		err = os.Rename(newFstabFile, fstabFile+".old")
+		if err != nil {
+			cmdr.Warning.Println("Old Fstab file will keep .new suffix")
+			// ignore, backup is not neccessary to boot
+		}
+	}
+
+	return nil
+}

main.go

@@ -80,6 +80,9 @@ func main() {
 	unlockVar := cmd.NewUnlockVarCommand()
 	root.AddCommand(unlockVar)
 
+	mntSys := cmd.NewMountSysCommand()
+	root.AddCommand(mntSys)
+
 	// run the app
 	err := abroot.Run()
 	if err != nil {