/
mount.go
104 lines (86 loc) · 2.65 KB
/
mount.go
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// 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
}
}