Add support for persistent disk when booting from ISO image

When booting from a LiveCD image there is no point in generating
a diffDisk because the OS is running from RAM, not from the disk.

In that case just add diffDisk as an independent data volume and
move directories that should be persisted on there. Currently:
/home, /usr/local, /etc/containerd, and /var/lib/containerd.

This data-volume logic is currently only enabled for Alpine because
it hasn't been tested anywhere else yet.

Additional, if the configured disk size is 0, no diffDisk will be
allocated and changes will be written back to the baseDisk (or
discarded, if the baseDisk is an ISO image).

Signed-off-by: Jan Dubois <[email protected]>

Author: jandubois

pkg/cidata/user-data.TEMPLATE

@@ -18,6 +18,75 @@ users:
     {{- end}}
 
 write_files:
+ - content: |
+      #!/bin/sh
+      # This script pretends that /bin/ash can be used as /bin/bash, so all following
+      # cloud-init scripts can use `#!/bin/bash` and `set -o pipefail`.
+      test -f /etc/alpine-release || exit 0
+
+      # Redirect bash to ash (built with CONFIG_ASH_BASH_COMPAT) and hope for the best :)
+      # It does support `set -o pipefail`, but not `[[`.
+      # /bin/bash can't be a symlink because /bin/ash is a symlink to /bin/busybox
+      cat >/bin/bash <<'EOF'
+      #!/bin/sh
+      exec /bin/ash "$@"
+      EOF
+      chmod +x /bin/bash
+   owner: root:root
+   path: /var/lib/cloud/scripts/per-boot/00-alpine-ash-as-bash.boot.sh
+   permissions: '0755'
+ - content: |
+      #!/bin/bash
+      set -eux -o pipefail
+
+      # Restrict the rest of this script to Alpine until it has been tested with other distros
+      test -f /etc/alpine-release || exit 0
+
+      # Data directories that should be persisted across reboots
+      DATADIRS="/home /usr/local /etc/containerd /var/lib/containerd"
+
+      # When running from RAM try to move persistent data to data-volume
+      # FIXME: the test for tmpfs mounts is probably Alpine-specific
+      if [ "$(awk '$2 == "/" {print $3}' /proc/mounts)" == "tmpfs" ]; then
+        mkdir -p /mnt/data
+        if [ -e /dev/disk/by-label/data-volume ]; then
+          mount -t ext4 /dev/disk/by-label/data-volume /mnt/data
+        else
+          # Find an unpartitioned disk and create data-volume
+          DISKS=$(lsblk --list --noheadings --output name,type | awk '$2 == "disk" {print $1}')
+          for DISK in ${DISKS}; do
+            IN_USE=false
+            # Looking for a disk that is not mounted or partitioned
+            for PART in $(awk '/^\/dev\// {gsub("/dev/", ""); print $1}' /proc/mounts); do
+              if [ "${DISK}" == "${PART}" -o -e /sys/block/${DISK}/${PART} ]; then
+                IN_USE=true
+                break
+              fi
+            done
+            if [ "${IN_USE}" == "false" ]; then
+              echo 'type=83' | sfdisk --label dos /dev/${DISK}
+              PART=$(lsblk --list /dev/${DISK} --noheadings --output name,type | awk '$2 == "part" {print $1}')
+              mkfs.ext4 -L data-volume /dev/${PART}
+              mount -t ext4 /dev/disk/by-label/data-volume /mnt/data
+              for DIR in ${DATADIRS}; do
+                DEST="/mnt/data$(dirname ${DIR})"
+                mkdir -p ${DIR} ${DEST}
+                mv ${DIR} ${DEST}
+              done
+              break
+            fi
+          done
+        fi
+        for DIR in ${DATADIRS}; do
+          if [ -d /mnt/data${DIR} ]; then
+            [ -e ${DIR} ] && rm -rf ${DIR}
+            ln -s /mnt/data${DIR} ${DIR}
+          fi
+        done
+      fi
+   owner: root:root
+   path: /var/lib/cloud/scripts/per-boot/05-persistent-data-volume.boot.sh
+   permissions: '0755'
  - content: |
       #!/sbin/openrc-run
       supervisor=supervise-daemon
@@ -35,34 +104,24 @@ write_files:
    path: /var/lib/lima-guestagent/lima-guestagent.openrc
    permissions: '0755'
  - content: |
-      #!/bin/sh
-      # This script prepares Alpine for lima; there is nothing in here for other distros
-      test -f /etc/alpine-release || exit
-
-      # Since we are on Alpine, we can now assume /bin/sh is /bin/ash
+      #!/bin/bash
       set -eux -o pipefail
 
-      # Redirect bash to ash (built with CONFIG_ASH_BASH_COMPAT) and hope for the best :)
-      # (it does support `set -o pipefail`, but not `[[`)
-      # /bin/bash can't be a symlink because /bin/ash is a symlink to /bin/busybox
-      cat >/bin/bash <<'EOF'
-      #!/bin/sh
-      exec /bin/ash "$@"
-      EOF
-      chmod +x /bin/bash
+      # This script prepares Alpine for lima; there is nothing in here for other distros
+      test -f /etc/alpine-release || exit 0
 
       # Configure apk repos
-      branch=edge
+      BRANCH=edge
       VERSION_ID=$(awk -F= '$1=="VERSION_ID" {print $2}' /etc/os-release)
-      case $VERSION_ID in
-      *_alpha*|*_beta*) branch=edge;;
-      *.*.*) branch=v${VERSION_ID%.*};;
+      case ${VERSION_ID} in
+      *_alpha*|*_beta*) BRANCH=edge;;
+      *.*.*) BRANCH=v${VERSION_ID%.*};;
       esac
 
-      for repo in main community; do
-        url="https://dl-cdn.alpinelinux.org/alpine/${branch}/${repo}"
-        if ! grep -q "^${url}$" /etc/apk/repositories; then
-          echo "${url}" >> /etc/apk/repositories
+      for REPO in main community; do
+        URL="https://dl-cdn.alpinelinux.org/alpine/${BRANCH}/${REPO}"
+        if ! grep -q "^${URL}$" /etc/apk/repositories; then
+          echo "${URL}" >> /etc/apk/repositories
         fi
       done
 
@@ -85,7 +144,7 @@ write_files:
       rc-update add acpid
       rc-service acpid start
    owner: root:root
-   path: /var/lib/cloud/scripts/per-boot/00-alpine-prep.boot.sh
+   path: /var/lib/cloud/scripts/per-boot/10-alpine-prep.boot.sh
    permissions: '0755'
  - content: |
       #!/bin/bash
@@ -159,7 +218,7 @@ write_files:
       fi
    owner: root:root
    # We do not use per-once.
-   path: /var/lib/cloud/scripts/per-boot/10-base.boot.sh
+   path: /var/lib/cloud/scripts/per-boot/20-base.boot.sh
    permissions: '0755'
  {{- if or .Mounts .Containerd.System .Containerd.User }}
  - content: |
@@ -210,7 +269,7 @@ write_files:
       fi
       {{- end}}
    owner: root:root
-   path: /var/lib/cloud/scripts/per-boot/20-install-packages.boot.sh
+   path: /var/lib/cloud/scripts/per-boot/30-install-packages.boot.sh
    permissions: '0755'
 {{- end}}
 {{- if or .Containerd.System .Containerd.User}}
@@ -274,7 +333,7 @@ write_files:
       fi
       {{- end}}
    owner: root:root
-   path: /var/lib/cloud/scripts/per-boot/30-install-containerd.boot.sh
+   path: /var/lib/cloud/scripts/per-boot/40-install-containerd.boot.sh
    permissions: '0755'
 {{- end}}
 {{- if .Provision}}
@@ -291,7 +350,7 @@ write_files:
       {{- end}}
       {{- end}}
    owner: root:root
-   path: /var/lib/cloud/scripts/per-boot/40-execute-provision-scripts.boot.sh
+   path: /var/lib/cloud/scripts/per-boot/50-execute-provision-scripts.boot.sh
    permissions: '0755'
 {{- end}}
 {{- range $i, $val := .Provision}}

pkg/iso9660util/iso9660util.go

@@ -60,3 +60,18 @@ func WriteFile(fs filesystem.FileSystem, path string, r io.Reader) (int64, error
 	defer f.Close()
 	return io.Copy(f, r)
 }
+
+func IsISO9660(imagePath string) (bool, error) {
+	imageFile, err := os.Open(imagePath)
+	if err != nil {
+		return false, err
+	}
+	defer imageFile.Close()
+
+	fileInfo, err := imageFile.Stat()
+	if err != nil {
+		return false, err
+	}
+	_, err = iso9660.Read(imageFile, fileInfo.Size(), 0, 0)
+	return err == nil, nil
+}

pkg/qemu/qemu.go

@@ -9,6 +9,7 @@ import (
 	"strconv"
 
 	"github.com/AkihiroSuda/lima/pkg/downloader"
+	"github.com/AkihiroSuda/lima/pkg/iso9660util"
 	"github.com/AkihiroSuda/lima/pkg/limayaml"
 	"github.com/AkihiroSuda/lima/pkg/store/filenames"
 	"github.com/docker/go-units"
@@ -60,15 +61,20 @@ func EnsureDisk(cfg Config) error {
 				len(cfg.LimaYAML.Images), errs)
 		}
 	}
-	diskSize, err := units.RAMInBytes(cfg.LimaYAML.Disk)
+	diskSize, _ := units.RAMInBytes(cfg.LimaYAML.Disk)
+	if diskSize == 0 {
+		return nil
+	}
+	isBaseDiskISO, err := iso9660util.IsISO9660(baseDisk)
 	if err != nil {
 		return err
 	}
-	cmd := exec.Command("qemu-img", "create",
-		"-f", "qcow2",
-		"-b", baseDisk,
-		diffDisk,
-		strconv.Itoa(int(diskSize)))
+	args := []string{"create", "-f", "qcow2"}
+	if !isBaseDiskISO {
+		args = append(args, "-b", baseDisk)
+	}
+	args = append(args, diffDisk, strconv.Itoa(int(diskSize)))
+	cmd := exec.Command("qemu-img", args...)
 	if out, err := cmd.CombinedOutput(); err != nil {
 		return errors.Wrapf(err, "failed to run %v: %q", cmd.Args, string(out))
 	}
@@ -118,11 +124,24 @@ func Cmdline(cfg Config) (string, []string, error) {
 	} else if y.Arch != limayaml.X8664 {
 		logrus.Warnf("field `firmware.legacyBIOS` is not supported for architecture %q, ignoring", y.Arch)
 	}
-	args = append(args, "-boot", "order=c,splash-time=0,menu=on")
-
-	// Root disk
-	args = append(args, "-drive", fmt.Sprintf("file=%s,if=virtio", filepath.Join(cfg.InstanceDir, filenames.DiffDisk)))
 
+	baseDisk := filepath.Join(cfg.InstanceDir, filenames.BaseDisk)
+	diffDisk := filepath.Join(cfg.InstanceDir, filenames.DiffDisk)
+	isBaseDiskCDROM, err := iso9660util.IsISO9660(baseDisk)
+	if err != nil {
+		return "", nil, err
+	}
+	if isBaseDiskCDROM {
+		args = append(args, "-boot", "order=d,splash-time=0,menu=on")
+		args = append(args, "-drive", fmt.Sprintf("file=%s,media=cdrom,readonly=on", baseDisk))
+	} else {
+		args = append(args, "-boot", "order=c,splash-time=0,menu=on")
+	}
+	if diskSize, _ := units.RAMInBytes(cfg.LimaYAML.Disk); diskSize > 0 {
+		args = append(args, "-drive", fmt.Sprintf("file=%s,if=virtio", diffDisk))
+	} else if !isBaseDiskCDROM {
+		args = append(args, "-drive", fmt.Sprintf("file=%s,if=virtio", baseDisk))
+	}
 	// cloud-init
 	args = append(args, "-cdrom", filepath.Join(cfg.InstanceDir, filenames.CIDataISO))