Support configuring mount locations within guests

Closes #659

Signed-off-by: Chance Zibolski <chance.zibolski@gmail.com>

examples/default.yaml

@@ -44,6 +44,9 @@ disk: null
 # 🔵 This file: Mount the home as read-only, /tmp/lima as writable
 mounts:
 - location: "~"
+  # Configure the mountPoint inside the guest.
+  # 🟢 Builtin default: value of location
+  mountPoint: null
   # CAUTION: `writable` SHOULD be false for the home directory.
   # Setting `writable` to true is possible, but untested and dangerous.
   # 🟢 Builtin default: false

pkg/cidata/cidata.go

@@ -134,6 +134,10 @@ func GenerateISO9660(instDir, name string, y *limayaml.LimaYAML, udpDNSLocalPort
 		if err != nil {
 			return err
 		}
+		target, err := localpathutil.Expand(f.MountPoint)
+		if err != nil {
+			return err
+		}
 		options := "defaults"
 		if fstype == "9p" {
 			options = "ro"
@@ -151,7 +155,7 @@ func GenerateISO9660(instDir, name string, y *limayaml.LimaYAML, udpDNSLocalPort
 			// don't fail the boot, if virtfs is not available
 			options += ",nofail"
 		}
-		args.Mounts = append(args.Mounts, Mount{Tag: tag, Target: expanded, Type: fstype, Options: options})
+		args.Mounts = append(args.Mounts, Mount{Tag: tag, Target: target, Type: fstype, Options: options})
 	}
 
 	switch *y.MountType {

pkg/hostagent/mount.go

@@ -38,6 +38,11 @@ func (a *HostAgent) setupMount(ctx context.Context, m limayaml.Mount) (*mount, e
 	if err != nil {
 		return nil, err
 	}
+
+	target, err := localpathutil.Expand(m.MountPoint)
+	if err != nil {
+		return nil, err
+	}
 	if err := os.MkdirAll(expanded, 0755); err != nil {
 		return nil, err
 	}
@@ -49,34 +54,35 @@ func (a *HostAgent) setupMount(ctx context.Context, m limayaml.Mount) (*mount, e
 	if *m.SSHFS.FollowSymlinks {
 		sshfsOptions = sshfsOptions + ",follow_symlinks"
 	}
-	logrus.Infof("Mounting %q", expanded)
+	logrus.Infof("Mounting host %q to guest %q", expanded, target)
+
 	rsf := &reversesshfs.ReverseSSHFS{
 		Driver:              *m.SSHFS.SFTPDriver,
 		SSHConfig:           a.sshConfig,
 		LocalPath:           expanded,
 		Host:                "127.0.0.1",
 		Port:                a.sshLocalPort,
-		RemotePath:          expanded,
+		RemotePath:          target,
 		Readonly:            !(*m.Writable),
 		SSHFSAdditionalArgs: []string{"-o", sshfsOptions},
 	}
 	if err := rsf.Prepare(); err != nil {
-		return nil, fmt.Errorf("failed to prepare reverse sshfs for %q: %w", expanded, err)
+		return nil, fmt.Errorf("failed to prepare reverse sshfs for %q->%q: %w", expanded, target, err)
 	}
 	if err := rsf.Start(); err != nil {
-		logrus.WithError(err).Warnf("failed to mount reverse sshfs for %q, retrying with `-o nonempty`", expanded)
+		logrus.WithError(err).Warnf("failed to mount reverse sshfs for %q->%q, retrying with `-o nonempty`", expanded, target)
 		// NOTE: nonempty is not supported for libfuse3: https://github.com/canonical/multipass/issues/1381
 		rsf.SSHFSAdditionalArgs = []string{"-o", "nonempty"}
 		if err := rsf.Start(); err != nil {
-			return nil, fmt.Errorf("failed to mount reverse sshfs for %q: %w", expanded, err)
+			return nil, fmt.Errorf("failed to mount reverse sshfs for %q->%q: %w", expanded, target, err)
 		}
 	}
 
 	res := &mount{
 		close: func() error {
 			logrus.Infof("Unmounting %q", expanded)
 			if closeErr := rsf.Close(); closeErr != nil {
-				return fmt.Errorf("failed to unmount reverse sshfs for %q: %w", expanded, err)
+				return fmt.Errorf("failed to unmount reverse sshfs for %q->%q: %w", expanded, target, err)
 			}
 			return nil
 		},

pkg/limayaml/defaults.go

@@ -402,6 +402,9 @@ func FillDefault(y, d, o *LimaYAML, filePath string) {
 			if mount.Writable != nil {
 				mounts[i].Writable = mount.Writable
 			}
+			if mount.MountPoint != "" {
+				mounts[i].MountPoint = mount.MountPoint
+			}
 		} else {
 			location[mount.Location] = len(mounts)
 			mounts = append(mounts, mount)
@@ -439,6 +442,9 @@ func FillDefault(y, d, o *LimaYAML, filePath string) {
 				mounts[i].NineP.Cache = pointer.String(Default9pCacheForRO)
 			}
 		}
+		if mount.MountPoint == "" {
+			mounts[i].MountPoint = mount.Location
+		}
 	}
 
 	if y.MountType == nil {

pkg/limayaml/defaults_test.go

@@ -145,6 +145,7 @@ func TestFillDefault(t *testing.T) {
 	}
 
 	expect.Mounts = y.Mounts
+	expect.Mounts[0].MountPoint = expect.Mounts[0].Location
 	expect.Mounts[0].Writable = pointer.Bool(false)
 	expect.Mounts[0].SSHFS.Cache = pointer.Bool(true)
 	expect.Mounts[0].SSHFS.FollowSymlinks = pointer.Bool(false)
@@ -299,6 +300,7 @@ func TestFillDefault(t *testing.T) {
 	expect = d
 	// Also verify that archive arch is filled in
 	expect.Containerd.Archives[0].Arch = *d.Arch
+	expect.Mounts[0].MountPoint = expect.Mounts[0].Location
 	expect.Mounts[0].SSHFS.Cache = pointer.Bool(true)
 	expect.Mounts[0].SSHFS.FollowSymlinks = pointer.Bool(false)
 	expect.Mounts[0].SSHFS.SFTPDriver = pointer.String("")

pkg/limayaml/limayaml.go

@@ -63,10 +63,11 @@ type Image struct {
 }
 
 type Mount struct {
-	Location string `yaml:"location" json:"location"` // REQUIRED
-	Writable *bool  `yaml:"writable,omitempty" json:"writable,omitempty"`
-	SSHFS    SSHFS  `yaml:"sshfs,omitempty" json:"sshfs,omitempty"`
-	NineP    NineP  `yaml:"9p,omitempty" json:"9p,omitempty"`
+	Location   string `yaml:"location" json:"location"` // REQUIRED
+	MountPoint string `yaml:"mountPoint,omitempty" json:"mountPoint,omitempty"`
+	Writable   *bool  `yaml:"writable,omitempty" json:"writable,omitempty"`
+	SSHFS      SSHFS  `yaml:"sshfs,omitempty" json:"sshfs,omitempty"`
+	NineP      NineP  `yaml:"9p,omitempty" json:"9p,omitempty"`
 }
 
 type SFTPDriver = string