vm: improve support for custom disk image

Signed-off-by: Abiola Ibrahim <[email protected]>

cmd/start.go

@@ -163,7 +163,7 @@ func init() {
 	startCmd.Flags().StringVarP(&startCmdArgs.Arch, "arch", "a", defaultArch, "architecture (aarch64, x86_64)")
 	startCmd.Flags().BoolVarP(&startCmdArgs.Flags.Foreground, "foreground", "f", false, "Keep colima in the foreground")
 	startCmd.Flags().StringVar(&startCmdArgs.Hostname, "hostname", "", "custom hostname for the virtual machine")
-	startCmd.Flags().StringVarP(&startCmdArgs.DiskImage, "disk-image", "i", "", "local path or URL to a custom disk image")
+	startCmd.Flags().StringVarP(&startCmdArgs.DiskImage, "disk-image", "i", "", "file path to a custom disk image")
 
 	// host IP addresses
 	startCmd.Flags().BoolVar(&startCmdArgs.Network.HostAddresses, "network-host-addresses", false, "support port forwarding to specific host IP addresses")

config/configmanager/configmanager.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/abiosoft/colima/cli"
 	"github.com/abiosoft/colima/config"
@@ -77,6 +78,12 @@ func ValidateConfig(c config.Config) error {
 		}
 	}
 
+	if c.DiskImage != "" {
+		if strings.HasPrefix(c.DiskImage, "http://") || strings.HasPrefix(c.DiskImage, "https://") {
+			return fmt.Errorf("cannot use diskImage: remote URLs not supported, only local files can be specified")
+		}
+	}
+
 	return nil
 }
 

embedded/defaults/colima.yaml

@@ -198,9 +198,9 @@ sshPort: 0
 mounts: []
 
 # Specify a custom disk image for the virtual machine.
-# When not specified, Colima downloads the disk image from Github at
+# When not specified, Colima downloads an appropriate disk image from Github at
 # https://github.com/abiosoft/colima-core/releases.
-# A custom disk image (local disk path or URL) can be specified to override the behaviour.
+# The file path to a custom disk image can be specified to override the behaviour.
 #
 # Default: ""
 diskImage: ""

environment/vm/lima/lima.go

@@ -16,6 +16,7 @@ import (
 	"github.com/abiosoft/colima/environment/vm/lima/limaconfig"
 	"github.com/abiosoft/colima/environment/vm/lima/limautil"
 	"github.com/abiosoft/colima/util"
+	"github.com/abiosoft/colima/util/downloader"
 	"github.com/abiosoft/colima/util/osutil"
 	"github.com/abiosoft/colima/util/yamlutil"
 	"github.com/sirupsen/logrus"
@@ -274,25 +275,33 @@ func (l limaVM) Arch() environment.Arch {
 func (l *limaVM) downloadDiskImage(ctx context.Context, conf config.Config) error {
 	log := l.Logger(ctx)
 
-	// use a previously cached image
-	if image, ok := limautil.ImageCached(l.limaConf.Arch, conf.Runtime); ok {
-		l.limaConf.Images = []limaconfig.File{image}
-		return nil
-	}
-
 	// use a user specified disk image
 	if conf.DiskImage != "" {
-		log.Infoln("using specified disk image ...")
+		if _, err := os.Stat(conf.DiskImage); err != nil {
+			return fmt.Errorf("invalid disk image: %w", err)
+		}
+
 		image, err := limautil.Image(l.limaConf.Arch, conf.Runtime)
 		if err != nil {
 			return fmt.Errorf("error getting disk image details: %w", err)
 		}
-		log.Warnf("disk image must be identical to '%s'", image.Location)
+
+		sha := downloader.SHA{Size: 512, Digest: image.Digest}
+		if err := sha.ValidateFile(l.host, conf.DiskImage); err != nil {
+			return fmt.Errorf("disk image must be downloaded from '%s', hash failure: %w", image.Location, err)
+		}
+
 		image.Location = conf.DiskImage
 		l.limaConf.Images = []limaconfig.File{image}
 		return nil
 	}
 
+	// use a previously cached image
+	if image, ok := limautil.ImageCached(l.limaConf.Arch, conf.Runtime); ok {
+		l.limaConf.Images = []limaconfig.File{image}
+		return nil
+	}
+
 	// download image
 	log.Infoln("downloading disk image ...")
 	image, err := limautil.DownloadImage(l.limaConf.Arch, conf.Runtime)

util/downloader/sha.go

@@ -17,10 +17,11 @@ type SHA struct {
 // ValidateFile validates the SHA of the file.
 func (s SHA) ValidateFile(host hostActions, file string) error {
 	dir, filename := filepath.Split(file)
+	digest := strings.TrimPrefix(s.Digest, fmt.Sprintf("sha%d:", s.Size))
 
 	script := strings.NewReplacer(
 		"{dir}", dir,
-		"{digest}", s.Digest,
+		"{digest}", digest,
 		"{size}", strconv.Itoa(s.Size),
 		"{filename}", filename,
 	).Replace(
@@ -35,10 +36,6 @@ func (s SHA) validateDownload(host hostActions, url string, filename string) err
 		return fmt.Errorf("error validating SHA: one of Digest or URL must be set")
 	}
 
-	if s.Digest != "" {
-		s.Digest = strings.TrimPrefix(s.Digest, fmt.Sprintf("sha%d:", s.Size))
-	}
-
 	// fetch digest from URL if empty
 	if s.Digest == "" {
 		// retrieve the filename from the download url.