github.com/hugh712/snapd@v0.0.0-20200910133618-1a99902bd583/overlord/snapstate/readme.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2017 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 snapstate
    21  
    22  import (
    23  	"os"
    24  	"strings"
    25  
    26  	"github.com/snapcore/snapd/dirs"
    27  	"github.com/snapcore/snapd/osutil"
    28  )
    29  
    30  const snapREADME = `
    31  This directory presents installed snap packages.
    32  
    33  It has the following structure:
    34  
    35  @SNAP_MOUNT_DIR@/bin                   - Symlinks to snap applications.
    36  @SNAP_MOUNT_DIR@/<snapname>/<revision> - Mountpoint for snap content.
    37  @SNAP_MOUNT_DIR@/<snapname>/current    - Symlink to current revision, if enabled.
    38  
    39  DISK SPACE USAGE
    40  
    41  The disk space consumed by the content under this directory is
    42  minimal as the real snap content never leaves the .snap file.
    43  Snaps are *mounted* rather than unpacked.
    44  
    45  For further details please visit
    46  https://forum.snapcraft.io/t/the-snap-directory/2817
    47  `
    48  
    49  func snapReadme() string {
    50  	return strings.Replace(snapREADME, "@SNAP_MOUNT_DIR@", dirs.SnapMountDir, -1)
    51  }
    52  
    53  func writeSnapReadme() error {
    54  	const fname = "README"
    55  	content := map[string]osutil.FileState{
    56  		fname: &osutil.MemoryFileState{Content: []byte(snapReadme()), Mode: 0444},
    57  	}
    58  	if err := os.MkdirAll(dirs.SnapMountDir, 0755); err != nil {
    59  		return err
    60  	}
    61  	// NOTE: We are using EnsureDirState to not unconditionally write to flash
    62  	// and thus prolong life of the device.
    63  	_, _, err := osutil.EnsureDirState(dirs.SnapMountDir, fname, content)
    64  	return err
    65  }