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packer_ext3_linux.go
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packer_ext3_linux.go
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// Copyright (c) 2019, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.
package sources
import (
"bytes"
"fmt"
"io/ioutil"
"os"
"os/exec"
"syscall"
args "github.com/sylabs/singularity/internal/pkg/runtime/engines/singularity/rpc"
"github.com/sylabs/singularity/internal/pkg/sylog"
"github.com/sylabs/singularity/pkg/build/types"
"github.com/sylabs/singularity/pkg/util/loop"
)
// Pack puts relevant objects in a Bundle!
func (p *Ext3Packer) Pack() (*types.Bundle, error) {
rootfs := p.srcfile
err := p.unpackExt3(p.b, p.info, rootfs)
if err != nil {
sylog.Errorf("unpackExt3 Failed: %s", err)
return nil, err
}
return p.b, nil
}
// unpackExt3 mounts the ext3 image using a loop device and then copies its contents to the bundle
func (p *Ext3Packer) unpackExt3(b *types.Bundle, info *loop.Info64, rootfs string) error {
tmpmnt, err := ioutil.TempDir(p.b.Path, "mnt")
if err != nil {
return fmt.Errorf("While making tmp mount point: %v", err)
}
var number int
info.Flags = loop.FlagsAutoClear
arguments := &args.LoopArgs{
Image: rootfs,
Mode: os.O_RDONLY,
Info: *info,
}
if err := getLoopDevice(arguments); err != nil {
return err
}
path := fmt.Sprintf("/dev/loop%d", number)
sylog.Debugf("Mounting loop device %s to %s\n", path, tmpmnt)
err = syscall.Mount(path, tmpmnt, "ext3", syscall.MS_NOSUID|syscall.MS_RDONLY|syscall.MS_NODEV, "errors=remount-ro")
if err != nil {
return fmt.Errorf("While mounting image: %v", err)
}
defer syscall.Unmount(tmpmnt, 0)
// copy filesystem into bundle rootfs
sylog.Debugf("Copying filesystem from %s to %s in Bundle\n", tmpmnt, b.Rootfs())
var stderr bytes.Buffer
cmd := exec.Command("cp", "-r", tmpmnt+`/.`, b.Rootfs())
cmd.Stderr = &stderr
if err := cmd.Run(); err != nil {
return fmt.Errorf("While copying files: %v: %v", err, stderr.String())
}
return err
}
// getLoopDevice attaches a loop device with the specified arguments
func getLoopDevice(arguments *args.LoopArgs) error {
var reply int
reply = 1
loopdev := new(loop.Device)
loopdev.MaxLoopDevices = 256
loopdev.Info = &arguments.Info
loopdev.Shared = arguments.Shared
return loopdev.AttachFromPath(arguments.Image, arguments.Mode, &reply)
}