backend

Documentation

Overview

Package backend implements the low-level primitives to manage the snaps and their installation on disk.

• Copyright (C) 2020 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/>. *

Index

• func GenerateSnapdWrappers(s *snap.Info) error
• func OpenSnapFile(snapPath string, sideInfo *snap.SideInfo) (*snap.Info, snap.Container, error)
• func WithSnapLock(info *snap.Info, action func() error) error
• type Alias
• type Backend
  • func NewForPreseedMode() Backend
  • func (b Backend) Candidate(*snap.SideInfo)
  • func (b Backend) ClearTrashedData(oldSnap *snap.Info)
  • func (b Backend) CopySnapData(newSnap, oldSnap *snap.Info, meter progress.Meter) error
  • func (b Backend) CurrentInfo(*snap.Info)
  • func (b Backend) DiscardSnapNamespace(snapName string) error
  • func (b Backend) LinkSnap(info *snap.Info, dev boot.Device, linkCtx LinkContext, tm timings.Measurer) (rebootRequired bool, e error)
  • func (b Backend) QueryDisabledServices(info *snap.Info, pb progress.Meter) ([]string, error)
  • func (b Backend) RemoveSnapAliases(snapName string) error
  • func (b Backend) RemoveSnapCommonData(snap *snap.Info) error
  • func (b Backend) RemoveSnapData(snap *snap.Info) error
  • func (b Backend) RemoveSnapDataDir(info *snap.Info, hasOtherInstances bool) error
  • func (b Backend) RemoveSnapDir(s snap.PlaceInfo, hasOtherInstances bool) error
  • func (b Backend) RemoveSnapFiles(s snap.PlaceInfo, typ snap.Type, installRecord *InstallRecord, dev boot.Device, ...) error
  • func (b Backend) RemoveSnapInhibitLock(instanceName string) error
  • func (b Backend) RunInhibitSnapForUnlink(info *snap.Info, hint runinhibit.Hint, decision func() error) (lock *osutil.FileLock, err error)
  • func (b Backend) ServicesEnableState(info *snap.Info, meter progress.Meter) (map[string]bool, error)
  • func (b Backend) SetupSnap(snapFilePath, instanceName string, sideInfo *snap.SideInfo, dev boot.Device, ...) (snapType snap.Type, installRecord *InstallRecord, err error)
  • func (b Backend) StartServices(apps []*snap.AppInfo, disabledSvcs []string, meter progress.Meter, ...) error
  • func (b Backend) StopServices(apps []*snap.AppInfo, reason snap.ServiceStopReason, meter progress.Meter, ...) error
  • func (b Backend) UndoCopySnapData(newInfo *snap.Info, oldInfo *snap.Info, meter progress.Meter) error
  • func (b Backend) UndoSetupSnap(s snap.PlaceInfo, typ snap.Type, installRecord *InstallRecord, dev boot.Device, ...) error
  • func (b Backend) UnlinkSnap(info *snap.Info, linkCtx LinkContext, meter progress.Meter) error
  • func (b Backend) UpdateAliases(add []*Alias, remove []*Alias) error
• type InstallRecord
• type LinkContext
• type SetupSnapOptions

Functions

func GenerateSnapdWrappers

func GenerateSnapdWrappers(s *snap.Info) error

func OpenSnapFile

func OpenSnapFile(snapPath string, sideInfo *snap.SideInfo) (*snap.Info, snap.Container, error)

OpenSnapFile opens a snap blob returning both a snap.Info completed with sideInfo (if not nil) and a corresponding snap.Container. Assumes the file was verified beforehand or the user asked for --dangerous.

func WithSnapLock

func WithSnapLock(info *snap.Info, action func() error) error

WithSnapLock executes given action with the snap lock held.

The lock is also used by snap-confine during pre-snap mount namespace initialization. Holding it allows to ensure mutual exclusion during the process of preparing a new snap app or hook processes. It does not prevent existing application or hook processes from forking.

Note that this is not a method of the Backend type, so that it can be invoked from doInstall, which does not have access to a backend object.

Types

type Alias

type Alias struct {
	Name   string `json:"name"`
	Target string `json:"target"`
}

Alias represents a command alias with a name and its application target.

type Backend

type Backend struct {
	// contains filtered or unexported fields
}

Backend exposes all the low-level primitives to manage snaps and their installation on disk.

func NewForPreseedMode

func NewForPreseedMode() Backend

func (Backend) Candidate

func (b Backend) Candidate(*snap.SideInfo)

Candidate is a test hook.

func (Backend) ClearTrashedData

func (b Backend) ClearTrashedData(oldSnap *snap.Info)

ClearTrashedData removes the trash. It returns no errors on the assumption that it is called very late in the game.

func (Backend) CopySnapData

func (b Backend) CopySnapData(newSnap, oldSnap *snap.Info, meter progress.Meter) error

CopySnapData makes a copy of oldSnap data for newSnap in its data directories.

func (Backend) CurrentInfo

func (b Backend) CurrentInfo(*snap.Info)

CurrentInfo is a test hook.

func (Backend) DiscardSnapNamespace

func (b Backend) DiscardSnapNamespace(snapName string) error

Discard the mount namespace of a given snap.

func (Backend) LinkSnap

func (b Backend) LinkSnap(info *snap.Info, dev boot.Device, linkCtx LinkContext, tm timings.Measurer) (rebootRequired bool, e error)

LinkSnap makes the snap available by generating wrappers and setting the current symlinks.

func (Backend) QueryDisabledServices

func (b Backend) QueryDisabledServices(info *snap.Info, pb progress.Meter) ([]string, error)

func (Backend) RemoveSnapAliases

func (b Backend) RemoveSnapAliases(snapName string) error

RemoveSnapAliases removes all the aliases targeting the given snap.

func (Backend) RemoveSnapCommonData

func (b Backend) RemoveSnapCommonData(snap *snap.Info) error

RemoveSnapCommonData removes the data common between versions of the given snap.

func (Backend) RemoveSnapData

func (b Backend) RemoveSnapData(snap *snap.Info) error

RemoveSnapData removes the data for the given version of the given snap.

func (Backend) RemoveSnapDataDir

func (b Backend) RemoveSnapDataDir(info *snap.Info, hasOtherInstances bool) error

RemoveSnapDataDir removes base snap data directory

func (Backend) RemoveSnapDir

func (b Backend) RemoveSnapDir(s snap.PlaceInfo, hasOtherInstances bool) error

func (Backend) RemoveSnapFiles

func (b Backend) RemoveSnapFiles(s snap.PlaceInfo, typ snap.Type, installRecord *InstallRecord, dev boot.Device, meter progress.Meter) error

RemoveSnapFiles removes the snap files from the disk after unmounting the snap.

func (Backend) RemoveSnapInhibitLock

func (b Backend) RemoveSnapInhibitLock(instanceName string) error

RemoveSnapInhibitLock removes the file controlling inhibition of "snap run".

func (Backend) RunInhibitSnapForUnlink

func (b Backend) RunInhibitSnapForUnlink(info *snap.Info, hint runinhibit.Hint, decision func() error) (lock *osutil.FileLock, err error)

func (Backend) ServicesEnableState

func (b Backend) ServicesEnableState(info *snap.Info, meter progress.Meter) (map[string]bool, error)

ServicesEnableState returns the current enabled/disabled states of a snap's services, primarily for committing before snap removal/disable/revert.

func (Backend) SetupSnap

func (b Backend) SetupSnap(snapFilePath, instanceName string, sideInfo *snap.SideInfo, dev boot.Device, setupOpts *SetupSnapOptions, meter progress.Meter) (snapType snap.Type, installRecord *InstallRecord, err error)

SetupSnap does prepare and mount the snap for further processing.

func (Backend) StartServices

func (b Backend) StartServices(apps []*snap.AppInfo, disabledSvcs []string, meter progress.Meter, tm timings.Measurer) error

func (Backend) StopServices

func (b Backend) StopServices(apps []*snap.AppInfo, reason snap.ServiceStopReason, meter progress.Meter, tm timings.Measurer) error

func (Backend) UndoCopySnapData

func (b Backend) UndoCopySnapData(newInfo *snap.Info, oldInfo *snap.Info, meter progress.Meter) error

UndoCopySnapData removes the copy that may have been done for newInfo snap of oldInfo snap data and also the data directories that may have been created for newInfo snap.

func (Backend) UndoSetupSnap

func (b Backend) UndoSetupSnap(s snap.PlaceInfo, typ snap.Type, installRecord *InstallRecord, dev boot.Device, meter progress.Meter) error

UndoSetupSnap undoes the work of SetupSnap using RemoveSnapFiles.

func (Backend) UnlinkSnap

func (b Backend) UnlinkSnap(info *snap.Info, linkCtx LinkContext, meter progress.Meter) error

UnlinkSnap makes the snap unavailable to the system removing wrappers and symlinks. The firstInstallUndo is true when undoing the first installation of the snap.

func (Backend) UpdateAliases

func (b Backend) UpdateAliases(add []*Alias, remove []*Alias) error

UpdateAliases adds and removes the given aliases.

type InstallRecord

type InstallRecord struct {
	// TargetSnapExisted indicates that the target .snap file under /var/lib/snapd/snap already existed when the
	// backend attempted SetupSnap() through squashfs Install() and should be kept.
	TargetSnapExisted bool `json:"target-snap-existed,omitempty"`
}

InstallRecord keeps a record of what installation effectively did as hints about what needs to be undone in case of failure.

type LinkContext

type LinkContext struct {
	// FirstInstall indicates whether this is the first time given snap is
	// installed
	FirstInstall bool

	// ServiceOptions is used to configure services.
	ServiceOptions *wrappers.SnapServiceOptions

	// RunInhibitHint is used only in Unlink snap, and can be used to
	// establish run inhibition lock for refresh operations.
	RunInhibitHint runinhibit.Hint

	// RequireMountedSnapdSnap indicates that the apps and services
	// generated when linking need to use tooling from the snapd snap mount.
	RequireMountedSnapdSnap bool
}

LinkContext carries additional information about the current or the previous state of the snap

type SetupSnapOptions

type SetupSnapOptions struct {
	SkipKernelExtraction bool
}