Experimental Mount Command

cmd/siftool/siftool.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2018-2022, Sylabs Inc. All rights reserved.
 // Copyright (c) 2017, SingularityWare, LLC. All rights reserved.
 // Copyright (c) 2017, Yannick Cote <yhcote@gmail.com> All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
@@ -12,6 +12,7 @@ import (
 	"io"
 	"os"
 	"runtime"
+	"strconv"
 	"text/tabwriter"
 
 	"github.com/spf13/cobra"
@@ -79,7 +80,16 @@ possible to modify a SIF file via this tool via the add/del commands.`,
 
 	root.AddCommand(getVersion())
 
-	if err := siftool.AddCommands(&root); err != nil {
+	var experimental bool
+	if val, ok := os.LookupEnv("SIFTOOL_EXPERIMENTAL"); ok {
+		b, err := strconv.ParseBool(val)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "Error: failed to parse SIFTOOL_EXPERIMENTAL environment variable:", err)
+		}
+		experimental = b
+	}
+
+	if err := siftool.AddCommands(&root, siftool.OptWithExperimental(experimental)); err != nil {
 		fmt.Fprintln(os.Stderr, "Error:", err)
 		os.Exit(1)
 	}

internal/app/siftool/app.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -13,6 +13,7 @@ import (
 // appOpts contains configured options.
 type appOpts struct {
 	out io.Writer
+	err io.Writer
 }
 
 // AppOpt are used to configure optional behavior.
@@ -31,11 +32,23 @@ func OptAppOutput(w io.Writer) AppOpt {
 	}
 }
 
+// OptAppError specifies that errors should be written to w.
+func OptAppError(w io.Writer) AppOpt {
+	return func(o *appOpts) error {
+		o.err = w
+		return nil
+	}
+}
+
 // New creates a new App configured with opts.
+//
+// By default, application output and errors are written to os.Stdout and os.Stderr respectively.
+// To modify this behavior, consider using OptAppOutput and/or OptAppError.
 func New(opts ...AppOpt) (*App, error) {
 	a := App{
 		opts: appOpts{
 			out: os.Stdout,
+			err: os.Stderr,
 		},
 	}
 

internal/app/siftool/mount.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2022, Sylabs Inc. All rights reserved.
+// This software is licensed under a 3-clause BSD license. Please consult the
+// LICENSE file distributed with the sources of this project regarding your
+// rights to use or distribute this software.
+
+package siftool
+
+import (
+	"context"
+
+	"github.com/sylabs/sif/v2/internal/pkg/exp"
+)
+
+// Mount mounts the primary system partition of the SIF file at path into mountPath.
+func (a *App) Mount(ctx context.Context, path, mountPath string) error {
+	return exp.Mount(ctx, path, mountPath,
+		exp.OptMountStdout(a.opts.out),
+		exp.OptMountStderr(a.opts.err),
+	)
+}

internal/pkg/exp/mount.go

@@ -0,0 +1,104 @@
+// Copyright (c) 2022, Sylabs Inc. All rights reserved.
+// This software is licensed under a 3-clause BSD license. Please consult the
+// LICENSE file distributed with the sources of this project regarding your
+// rights to use or distribute this software.
+
+// Package exp contains experimental functionality that is not sufficiently mature to be exported
+// as part of the module API.
+package exp
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/sylabs/sif/v2/pkg/sif"
+)
+
+// mountSquashFS mounts the SquashFS filesystem from path at offset into mountPath.
+func mountSquashFS(ctx context.Context, offset int64, path, mountPath string, mo mountOpts) error {
+	args := []string{
+		"-o", fmt.Sprintf("ro,offset=%d", offset),
+		filepath.Clean(path),
+		filepath.Clean(mountPath),
+	}
+
+	cmd := exec.CommandContext(ctx, "squashfuse", args...)
+	cmd.Stdout = mo.stdout
+	cmd.Stderr = mo.stderr
+
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("failed to mount: %w", err)
+	}
+
+	return nil
+}
+
+// mountOpts accumulates mount options.
+type mountOpts struct {
+	stdout io.Writer
+	stderr io.Writer
+}
+
+// MountOpt are used to specify mount options.
+type MountOpt func(*mountOpts) error
+
+// OptMountStdout writes standard output to w.
+func OptMountStdout(w io.Writer) MountOpt {
+	return func(mo *mountOpts) error {
+		mo.stdout = w
+		return nil
+	}
+}
+
+// OptMountStderr writes standard error to w.
+func OptMountStderr(w io.Writer) MountOpt {
+	return func(mo *mountOpts) error {
+		mo.stderr = w
+		return nil
+	}
+}
+
+var errUnsupportedFSType = errors.New("unrecognized filesystem type")
+
+// Mount mounts the primary system partition of the SIF file at path into mountPath.
+//
+// Mount may start one or more underlying processes. By default, stdout and stderr of these
+// processes is discarded. To modify this behavior, consider using OptMountStdout and/or
+// OptMountStderr.
+func Mount(ctx context.Context, path, mountPath string, opts ...MountOpt) error {
+	mo := mountOpts{}
+
+	for _, opt := range opts {
+		if err := opt(&mo); err != nil {
+			return fmt.Errorf("%w", err)
+		}
+	}
+
+	f, err := sif.LoadContainerFromPath(path, sif.OptLoadWithFlag(os.O_RDONLY))
+	if err != nil {
+		return fmt.Errorf("failed to load image: %w", err)
+	}
+	defer func() { _ = f.UnloadContainer() }()
+
+	d, err := f.GetDescriptor(sif.WithPartitionType(sif.PartPrimSys))
+	if err != nil {
+		return fmt.Errorf("failed to get partition descriptor: %w", err)
+	}
+
+	fs, _, _, err := d.PartitionMetadata()
+	if err != nil {
+		return fmt.Errorf("failed to get partition metadata: %w", err)
+	}
+
+	switch fs {
+	case sif.FsSquash:
+		return mountSquashFS(ctx, d.Offset(), path, mountPath, mo)
+	default:
+		return errUnsupportedFSType
+	}
+}

pkg/siftool/add_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -46,7 +46,7 @@ func Test_command_getAdd(t *testing.T) {
 			}
 			args = append(args, tt.flags...)
 
-			runCommand(t, cmd, args)
+			runCommand(t, cmd, args, nil)
 		})
 	}
 }

pkg/siftool/del_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -24,7 +24,7 @@ func Test_command_getDel(t *testing.T) {
 
 			cmd := c.getDel()
 
-			runCommand(t, cmd, []string{"1", makeTestSIF(t, true)})
+			runCommand(t, cmd, []string{"1", makeTestSIF(t, true)}, nil)
 		})
 	}
 }

pkg/siftool/dump_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -39,7 +39,7 @@ func Test_command_getDump(t *testing.T) {
 
 			cmd := c.getDump()
 
-			runCommand(t, cmd, []string{tt.id, tt.path})
+			runCommand(t, cmd, []string{tt.id, tt.path}, nil)
 		})
 	}
 }

pkg/siftool/header_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -68,7 +68,7 @@ func Test_command_getHeader(t *testing.T) {
 
 			cmd := c.getHeader()
 
-			runCommand(t, cmd, []string{tt.path})
+			runCommand(t, cmd, []string{tt.path}, nil)
 		})
 	}
 }

pkg/siftool/info_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -39,7 +39,7 @@ func Test_command_getInfo(t *testing.T) {
 
 			cmd := c.getInfo()
 
-			runCommand(t, cmd, []string{tt.id, tt.path})
+			runCommand(t, cmd, []string{tt.id, tt.path}, nil)
 		})
 	}
 }

pkg/siftool/list_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -68,7 +68,7 @@ func Test_command_getList(t *testing.T) {
 
 			cmd := c.getList()
 
-			runCommand(t, cmd, []string{tt.path})
+			runCommand(t, cmd, []string{tt.path}, nil)
 		})
 	}
 }

pkg/siftool/mount.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2022, Sylabs Inc. All rights reserved.
+// This software is licensed under a 3-clause BSD license. Please consult the
+// LICENSE file distributed with the sources of this project regarding your
+// rights to use or distribute this software.
+
+package siftool
+
+import (
+	"github.com/spf13/cobra"
+)
+
+// getMount returns a command that mounts the primary system partition of a SIF image.
+func (c *command) getMount() *cobra.Command {
+	return &cobra.Command{
+		Use:     "mount <sif_path> <mount_path>",
+		Short:   "Mount primary system partition",
+		Long:    "Mount the primary system partition of a SIF image",
+		Example: c.opts.rootPath + " mount image.sif path/",
+		Args:    cobra.ExactArgs(2),
+		PreRunE: c.initApp,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return c.app.Mount(cmd.Context(), args[0], args[1])
+		},
+		DisableFlagsInUseLine: true,
+		Hidden:                true, // hide while command is experimental
+	}
+}

pkg/siftool/mount_test.go

@@ -0,0 +1,61 @@
+// Copyright (c) 2022, Sylabs Inc. All rights reserved.
+// This software is licensed under a 3-clause BSD license. Please consult the
+// LICENSE file distributed with the sources of this project regarding your
+// rights to use or distribute this software.
+
+package siftool
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+
+	"github.com/sylabs/sif/v2/pkg/sif"
+)
+
+func Test_command_getMount(t *testing.T) {
+	if _, err := exec.LookPath("squashfuse"); err != nil {
+		t.Skip("squashfuse not found, skipping mount tests")
+	}
+
+	tests := []struct {
+		name    string
+		opts    commandOpts
+		path    string
+		wantErr error
+	}{
+		{
+			name:    "Empty",
+			path:    filepath.Join(corpus, "empty.sif"),
+			wantErr: sif.ErrNoObjects,
+		},
+		{
+			name: "OneGroup",
+			path: filepath.Join(corpus, "one-group.sif"),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			path, err := os.MkdirTemp("", "siftool-mount-*")
+			if err != nil {
+				t.Fatal(err)
+			}
+			t.Cleanup(func() {
+				cmd := exec.Command("fusermount", "-u", path)
+
+				if err := cmd.Run(); err != nil {
+					t.Log(err)
+				}
+
+				os.RemoveAll(path)
+			})
+
+			c := &command{opts: tt.opts}
+
+			cmd := c.getMount()
+
+			runCommand(t, cmd, []string{tt.path, path}, tt.wantErr)
+		})
+	}
+}

pkg/siftool/new_test.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2021, Sylabs Inc. All rights reserved.
+// Copyright (c) 2021-2022, Sylabs Inc. All rights reserved.
 // This software is licensed under a 3-clause BSD license. Please consult the
 // LICENSE file distributed with the sources of this project regarding your
 // rights to use or distribute this software.
@@ -32,7 +32,7 @@ func Test_command_getNew(t *testing.T) {
 
 			cmd := c.getNew()
 
-			runCommand(t, cmd, []string{tf.Name()})
+			runCommand(t, cmd, []string{tf.Name()}, nil)
 		})
 	}
 }