qemu: use 9p by default

AkihiroSuda · AkihiroSuda · commit 2b8d352c5c15 · 2024-07-02T16:36:48.000+09:00
Templates for the following distro are updated to continue using reverse-sshfs,
as 9p is not available on them.
- AlmaLinux
- CentOS Stream
- Debian
- openSUSE
- Oracle Linux
- Rocky Linux

Close issue 971

Signed-off-by: Akihiro Suda &lt;akihiro.suda.cz@hco.ntt.co.jp&gt;
diff --git a/examples/almalinux-8.yaml b/examples/almalinux-8.yaml
@@ -16,6 +16,8 @@ images:
   arch: "x86_64"
 - location: "https://repo.almalinux.org/almalinux/8/cloud/aarch64/images/AlmaLinux-8-GenericCloud-latest.aarch64.qcow2"
   arch: "aarch64"
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/almalinux-9.yaml b/examples/almalinux-9.yaml
@@ -13,6 +13,8 @@ images:
   arch: "x86_64"
 - location: "https://repo.almalinux.org/almalinux/9/cloud/aarch64/images/AlmaLinux-9-GenericCloud-latest.aarch64.qcow2"
   arch: "aarch64"
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/centos-stream-9.yaml b/examples/centos-stream-9.yaml
@@ -14,6 +14,8 @@ images:
   arch: "x86_64"
 - location: "https://cloud.centos.org/centos/9-stream/aarch64/images/CentOS-Stream-GenericCloud-9-latest.aarch64.qcow2"
   arch: "aarch64"
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/debian-11.yaml b/examples/debian-11.yaml
@@ -14,6 +14,8 @@ images:
 - location: "https://cloud.debian.org/images/cloud/bullseye/latest/debian-11-genericcloud-arm64.qcow2"
   arch: "aarch64"
 
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/debian-12.yaml b/examples/debian-12.yaml
@@ -14,6 +14,8 @@ images:
 - location: "https://cloud.debian.org/images/cloud/bookworm/latest/debian-12-genericcloud-arm64.qcow2"
   arch: "aarch64"
 
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/default.yaml b/examples/default.yaml
@@ -99,7 +99,7 @@ mounts:
 
 # Mount type for above mounts, such as "reverse-sshfs" (from sshocker), "9p" (EXPERIMENTAL (until Lima v1.0), from QEMU’s virtio-9p-pci, aka virtfs),
 # or "virtiofs" (EXPERIMENTAL, needs `vmType: vz`)
-# 🟢 Builtin default: "reverse-sshfs" (for QEMU), "virtiofs" (for vz)
+# 🟢 Builtin default: "9p" (for QEMU, since Lima v1.0), "virtiofs" (for vz)
 mountType: null
 
 # Enable inotify support for mounted directories (EXPERIMENTAL)
diff --git a/examples/experimental/opensuse-tumbleweed.yaml b/examples/experimental/opensuse-tumbleweed.yaml
@@ -17,6 +17,8 @@ images:
 - location: "https://provo-mirror.opensuse.org/ports/aarch64/tumbleweed/appliances/openSUSE-Tumbleweed-ARM-JeOS-efi.aarch64.qcow2"
   arch: "aarch64"
 
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/opensuse.yaml b/examples/opensuse.yaml
@@ -5,6 +5,8 @@ images:
   arch: "x86_64"
 - location: "https://download.opensuse.org/distribution/leap/15.5/appliances/openSUSE-Leap-15.5-Minimal-VM.aarch64-Cloud.qcow2"
   arch: "aarch64"
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/oraclelinux-8.yaml b/examples/oraclelinux-8.yaml
@@ -12,6 +12,8 @@ images:
 - location: "https://yum.oracle.com/templates/OracleLinux/OL8/u10/aarch64/OL8U10_aarch64-kvm-cloud-b100.qcow2"
   arch: "aarch64"
   digest: "sha256:def7b8055e275507a593f07dc6076a2adc5967af046c003072b479e69f25f407"
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/oraclelinux-9.yaml b/examples/oraclelinux-9.yaml
@@ -9,6 +9,8 @@ images:
 - location: "https://yum.oracle.com/templates/OracleLinux/OL9/u4/aarch64/OL9U4_aarch64-kvm-cloud-b90.qcow2"
   arch: "aarch64"
   digest: "sha256:1f4e20190e87c76e8c3b4a9e15e660972386cbfa4f128e5cdcd8faa43a713d44"
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/rocky-8.yaml b/examples/rocky-8.yaml
@@ -16,6 +16,8 @@ images:
   arch: "x86_64"
 - location: "https://dl.rockylinux.org/pub/rocky/8/images/aarch64/Rocky-8-GenericCloud.latest.aarch64.qcow2"
   arch: "aarch64"
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/examples/rocky-9.yaml b/examples/rocky-9.yaml
@@ -13,6 +13,8 @@ images:
   arch: "x86_64"
 - location: "https://dl.rockylinux.org/pub/rocky/9/images/aarch64/Rocky-9-GenericCloud.latest.aarch64.qcow2"
   arch: "aarch64"
+# The mount type is set to reverse-sshfs because 9p (default for QEMU) is not supported by the guest kernel. VZ users should specify `--mount-type=virtiofs` on `limactl create` for better performance.
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
 - location: "/tmp/lima"
diff --git a/hack/test-templates/test-misc.yaml b/hack/test-templates/test-misc.yaml
@@ -1,5 +1,6 @@
 # The test template for testing misc configurations:
 # - disk
+# - snapshots
 # - (More to come)
 #
 # This template requires Lima v0.14.0 or later.
@@ -18,6 +19,8 @@ images:
 - location: "https://cloud-images.ubuntu.com/releases/24.04/release/ubuntu-24.04-server-cloudimg-arm64.img"
   arch: "aarch64"
 
+# 9p is not compatible with `limactl snapshot`
+mountType: "reverse-sshfs"
 mounts:
 - location: "~"
   writable: true
diff --git a/pkg/limayaml/defaults.go b/pkg/limayaml/defaults.go
@@ -3,6 +3,7 @@ package limayaml
 import (
 	"bytes"
 	"crypto/sha256"
+	"errors"
 	"fmt"
 	"net"
 	"os"
@@ -23,6 +24,7 @@ import (
 	"github.com/lima-vm/lima/pkg/ptr"
 	"github.com/lima-vm/lima/pkg/store/dirnames"
 	"github.com/lima-vm/lima/pkg/store/filenames"
+	"github.com/lima-vm/lima/pkg/version/versionutil"
 )
 
 const (
@@ -172,6 +174,15 @@ func defaultGuestInstallPrefix() string {
 //   - CACertificates Files and Certs are uniquely appended in d, y, o order
 func FillDefault(y, d, o *LimaYAML, filePath string) {
 	instDir := filepath.Dir(filePath)
+
+	var existingLimaVersion string // empty if the instance was created with Lima prior to v0.20
+	limaVersionFile := filepath.Join(instDir, filenames.LimaVersion)
+	if b, err := os.ReadFile(limaVersionFile); err == nil {
+		existingLimaVersion = strings.TrimSpace(string(b))
+	} else if !errors.Is(err, os.ErrNotExist) {
+		logrus.WithError(err).Warnf("Failed to read %q", limaVersionFile)
+	}
+
 	if y.VMType == nil {
 		y.VMType = d.VMType
 	}
@@ -551,9 +562,24 @@ func FillDefault(y, d, o *LimaYAML, filePath string) {
 		y.MountType = o.MountType
 	}
 	if y.MountType == nil || *y.MountType == "" {
-		if *y.VMType == VZ {
+		switch *y.VMType {
+		case VZ:
 			y.MountType = ptr.Of(VIRTIOFS)
-		} else {
+		case QEMU:
+			y.MountType = ptr.Of(NINEP)
+			// Use REVSSHFS if the instance was created with Lima prior to v1.0
+			if _, err := os.Stat(filePath); err == nil { // existing instance
+				switch {
+				case existingLimaVersion == "": // created with Lima < 0.20
+					y.MountType = ptr.Of(REVSSHFS)
+				case strings.TrimPrefix(existingLimaVersion, "v") == "1.0.0",
+					versionutil.GreaterThan(existingLimaVersion, "1.0.0"):
+					// NOP
+				default: // created with 0.20 <= Lima < 1.0
+					y.MountType = ptr.Of(REVSSHFS)
+				}
+			}
+		default:
 			y.MountType = ptr.Of(REVSSHFS)
 		}
 	}
diff --git a/website/content/en/docs/faq/_index.md b/website/content/en/docs/faq/_index.md
@@ -32,6 +32,7 @@ weight: 6
 - [Filesystem sharing](#filesystem-sharing)
   - ["Filesystem is slow"](#filesystem-is-slow)
   - ["Filesystem is not writable"](#filesystem-is-not-writable)
+  - ["Filesystem is unmounted after upgrading Lima to v1.0 (pre-release)"](#filesystem-is-unmounted-after-upgrading-lima-to-v10-pre-release)
 - [External projects](#external-projects)
   - ["I am using Rancher Desktop. How to deal with the underlying Lima?"](#i-am-using-rancher-desktop-how-to-deal-with-the-underlying-lima)
 - ["Hints for debugging other problems?"](#hints-for-debugging-other-problems)
@@ -230,6 +231,24 @@ mounts:
 
 Run `limactl edit <INSTANCE>` to open the YAML editor for an existing instance.
 
+#### "Filesystem is unmounted after upgrading Lima to v1.0 (pre-release)"
+
+Lima v1.0 (pre-release) changed the default mount driver for QEMU from `reverse-sshfs` to `9p`.
+
+This change is known to be incompatible with the following guest operating systems:
+- AlmaLinux, CentOS Stream, Oracle Linux, and RockyLinux
+- Debian GNU/Linux
+- openSUSE
+
+A new instance of these OS still use `reverse-sshfs` by default, however,
+an existing instance created with a previous version of Lima needs running the following command:
+
+```
+limactl edit --mount-type=reverse-sshfs <NAME>
+```
+
+Ubuntu users are not affected by this issue.
+
 ### External projects
 #### "I am using Rancher Desktop. How to deal with the underlying Lima?"
 
