github.com/Lephar/snapd@v0.0.0-20210825215435-c7fba9cef4d2/osutil/squashfs/fstype.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2018 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package squashfs
    21  
    22  import (
    23  	"os/exec"
    24  	"strings"
    25  
    26  	"github.com/snapcore/snapd/osutil"
    27  )
    28  
    29  var needsFuseImpl = func() bool {
    30  	if !osutil.FileExists("/dev/fuse") {
    31  		return false
    32  	}
    33  
    34  	if !osutil.ExecutableExists("squashfuse") && !osutil.ExecutableExists("snapfuse") {
    35  		return false
    36  	}
    37  
    38  	out, err := exec.Command("systemd-detect-virt", "--container").Output()
    39  	if err != nil {
    40  		return false
    41  	}
    42  
    43  	virt := strings.TrimSpace(string(out))
    44  	if virt != "none" {
    45  		return true
    46  	}
    47  
    48  	return false
    49  }
    50  
    51  // MockNeedsFuse is exported so NeedsFuse can be overridden by testing.
    52  func MockNeedsFuse(r bool) func() {
    53  	oldNeedsFuseImpl := needsFuseImpl
    54  	needsFuseImpl = func() bool {
    55  		return r
    56  	}
    57  	return func() { needsFuseImpl = oldNeedsFuseImpl }
    58  }
    59  
    60  // NeedsFuse returns true if the given system needs fuse to mount snaps
    61  func NeedsFuse() bool {
    62  	return needsFuseImpl()
    63  }
    64  
    65  // StandardOptions returns base squashfs options.
    66  func StandardOptions() []string {
    67  	return []string{"ro", "x-gdu.hide", "x-gvfs-hide"}
    68  }
    69  
    70  // FsType returns what fstype to use for squashfs mounts and what
    71  // mount options
    72  func FsType() (fstype string, options []string) {
    73  	fstype = "squashfs"
    74  	options = StandardOptions()
    75  
    76  	if NeedsFuse() {
    77  		options = append(options, "allow_other")
    78  		switch {
    79  		case osutil.ExecutableExists("squashfuse"):
    80  			fstype = "fuse.squashfuse"
    81  		case osutil.ExecutableExists("snapfuse"):
    82  			fstype = "fuse.snapfuse"
    83  		default:
    84  			panic("cannot happen because NeedsFuse() ensures one of the two executables is there")
    85  		}
    86  	}
    87  
    88  	return fstype, options
    89  }