github.com/stulluk/snapd@v0.0.0-20210611110309-f6d5d5bd24b0/sysconfig/sysconfig.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2020 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 sysconfig
    21  
    22  import (
    23  	"path/filepath"
    24  
    25  	"github.com/snapcore/snapd/gadget"
    26  	"github.com/snapcore/snapd/snap"
    27  )
    28  
    29  // See https://github.com/snapcore/core20/pull/46
    30  const writableDefaultsDir = "_writable_defaults"
    31  
    32  // Options is the set of options used to configure the run system
    33  type Options struct {
    34  	// CloudInitSrcDir is where to find the cloud-init data when installing it,
    35  	// i.e. in early boot install mode it could be something like
    36  	// filepath.Join(boot.InitramfsUbuntuSeedDir,"data")
    37  	CloudInitSrcDir string
    38  
    39  	// TargetRootDir is the root directory where to install configure
    40  	// data, i.e. for cloud-init during the initramfs it will be something like
    41  	// boot.InstallHostWritableDir
    42  	TargetRootDir string
    43  
    44  	// AllowCloudInit is whether to allow cloud-init to run or not in the
    45  	// TargetRootDir.
    46  	AllowCloudInit bool
    47  
    48  	// GadgetDir is the path of the mounted gadget snap.
    49  	GadgetDir string
    50  
    51  	// GadgetSnap is a snap.Container of the gadget snap. This is used in
    52  	// priority over GadgetDir if set.
    53  	GadgetSnap snap.Container
    54  }
    55  
    56  // FilesystemOnlyApplyOptions is the set of options for
    57  // ApplyFilesystemOnlyDefaults.
    58  type FilesystemOnlyApplyOptions struct {
    59  	// Classic is true when the system in rootdir is a classic system
    60  	Classic bool
    61  }
    62  
    63  // ApplyFilesystemOnlyDefaultsImpl is initialized by init() of configcore.
    64  var ApplyFilesystemOnlyDefaultsImpl = func(rootDir string, defaults map[string]interface{}, options *FilesystemOnlyApplyOptions) error {
    65  	panic("ApplyFilesystemOnlyDefaultsImpl is unset, import overlord/configstate/configcore")
    66  }
    67  
    68  // ApplyFilesystemOnlyDefaults applies (via configcore.filesystemOnlyApply())
    69  // filesystem modifications under rootDir, according to the defaults.
    70  // This is a subset of core config options that is important
    71  // early during boot, before all the configuration is applied as part of
    72  // normal execution of configure hook.
    73  func ApplyFilesystemOnlyDefaults(rootDir string, defaults map[string]interface{}, options *FilesystemOnlyApplyOptions) error {
    74  	return ApplyFilesystemOnlyDefaultsImpl(rootDir, defaults, options)
    75  }
    76  
    77  // ConfigureTargetSystem configures the ubuntu-data partition with
    78  // any configuration needed from e.g. the gadget or for cloud-init (and also for
    79  // cloud-init from the gadget).
    80  // It is okay to use both from install mode for run mode, as well as from the
    81  // initramfs for recover mode.
    82  func ConfigureTargetSystem(opts *Options) error {
    83  	if err := configureCloudInit(opts); err != nil {
    84  		return err
    85  	}
    86  
    87  	var gadgetInfo *gadget.Info
    88  	var err error
    89  	switch {
    90  	case opts.GadgetSnap != nil:
    91  		// we do not perform consistency validation here because
    92  		// such unlikely problems are better surfaced in different
    93  		// and less surprising contexts like the seeding itself
    94  		gadgetInfo, err = gadget.ReadInfoFromSnapFileNoValidate(opts.GadgetSnap, nil)
    95  	case opts.GadgetDir != "":
    96  		gadgetInfo, err = gadget.ReadInfo(opts.GadgetDir, nil)
    97  	}
    98  
    99  	if err != nil {
   100  		return err
   101  	}
   102  
   103  	if gadgetInfo != nil {
   104  		defaults := gadget.SystemDefaults(gadgetInfo.Defaults)
   105  		if len(defaults) > 0 {
   106  			// options are nil which implies core system
   107  			var options *FilesystemOnlyApplyOptions
   108  			if err := ApplyFilesystemOnlyDefaults(WritableDefaultsDir(opts.TargetRootDir), defaults, options); err != nil {
   109  				return err
   110  			}
   111  		}
   112  	}
   113  
   114  	return nil
   115  }
   116  
   117  // WritableDefaultsDir returns the full path of the joined subdir under the
   118  // subtree for default content for system data living at rootdir,
   119  // i.e. rootdir/_writable_defaults/subdir...
   120  func WritableDefaultsDir(rootdir string, subdir ...string) string {
   121  	return filepath.Join(rootdir, writableDefaultsDir, filepath.Join(subdir...))
   122  }