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helpers.go
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/
helpers.go
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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2014-2015 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package classic
import (
"fmt"
"os"
"os/exec"
"path/filepath"
"strings"
"github.com/snapcore/snapd/dirs"
"github.com/snapcore/snapd/osutil"
)
// Enabled returns true if the classic mode is already enabled
func Enabled() bool {
return osutil.FileExists(filepath.Join(dirs.ClassicDir, "etc", "apt", "sources.list"))
}
var mountpointCmd = "mountpoint"
// isMounted returns true if the given path is a mountpoint
func isMounted(path string) (bool, error) {
cmd := exec.Command(mountpointCmd, path)
// mountpoint uses translated messages, ensure we get the
// english ones
cmd.Env = []string{"LC_ALL=C"}
output, err := cmd.CombinedOutput()
exitCode, err := osutil.ExitCode(err)
// if we get anything other than "ExitError" er error here
if err != nil {
return false, err
}
// mountpoint.c from util-linux always returns 0 or 1
// (unless e.g. signal)
if exitCode != 0 && exitCode != 1 {
return false, fmt.Errorf("got unexpected exit code %v from the mountpoint command: %s", exitCode, output)
}
// exitCode == 0 means it is a mountpoint, do we are done
if exitCode == 0 {
return true, nil
}
// exitCode == 1 either means something went wrong *or*
// the path is not a mount point
// (thanks mountpoint.c :/)
if strings.Contains(string(output), "is not a mountpoint") {
return false, nil
}
return false, fmt.Errorf("unexpected output from mountpoint: %s (%v)", output, exitCode)
}
// bindmount will bind mount the src path into the dstPath of the
// ubuntu classic environment
func bindmount(src, dstPath, remountArg string) error {
dst := filepath.Join(dirs.ClassicDir, dstPath)
alreadyMounted, err := isMounted(dst)
if err != nil {
return err
}
if alreadyMounted {
return nil
}
// see if we need to create the dir in dstPath
st, err := os.Stat(src)
if err != nil {
return err
}
if st.IsDir() && (st.Mode()&os.ModeSymlink == 0) {
if err := os.MkdirAll(dst, st.Mode().Perm()); err != nil {
return err
}
}
// do the actual mount, we use "rbind" so that we get all submounts
cmd := exec.Command("mount", "--make-rprivate", "--rbind", "-o", "rbind", src, dst)
if output, err := cmd.CombinedOutput(); err != nil {
return fmt.Errorf("bind mounting %s to %s failed: %s (%s)", src, dst, err, output)
}
// remount as needed (ro)
if remountArg != "" {
cmd := exec.Command("mount", "--rbind", "-o", "remount,"+remountArg, src, dst)
if output, err := cmd.CombinedOutput(); err != nil {
return fmt.Errorf("remount %s to %s failed: %s (%s)", src, dst, err, output)
}
}
return nil
}
func umount(path string) error {
if output, err := exec.Command("umount", path).CombinedOutput(); err != nil {
return fmt.Errorf("failed to umount %s: %s (%s)", path, err, output)
}
return nil
}