ConsoleKit 0.4.1 Documentation

ConsoleKit is a framework for keeping track of the various users, sessions, and seats present on a system. It provides a mechanism for software to react to changes of any of these items or of any of the metadata associated with them.

Defining the Problem

To be written.

Relevant art

To be written.

Chapter 2. Terminology

Table of Contents

Session
Session leader
Seat

Session

A session is a collection of all processes that share knowledge of a secret. In the typical (or ideal) case, these processes all originate from a single common ancestor.

As an implementation detail, for now, this secret should be stored in the process environment by the session leader under the name XDG_SESSION_COOKIE. When and if we are able to take advantage of a mechanism in the underlying system to store session registration information - we will. However, such a mechanism is not known at the present time.

Using an environment variable does have certain advantages. For one, it is quite easy for a process to opt-out of a Session by simply unsetting the XDG_SESSION_COOKIE variable.

Limitations of using an environment variable implementation include not being able to strictly limit visibility of the secret to a particular process ancestry. So, it is not possible to enforce session boundaries other than on a per-user basis. For example, we don't yet have a way to prevent a process from moving between sessions owned by the same user.

Session leader

The session leader is the process that requests that a new session be opened. It does this by connecting to the D-Bus system bus and using either org.freedesktop.ConsoleKit.Manager.OpenSession() or org.freedesktop.ConsoleKit.Manager.OpenSessionWithParameters(). The session that it registers will remain open until the connection to the system bus is lost or it calls org.freedesktop.ConsoleKit.Manager.CloseSession().

The session leader is the only process for which CloseSession() will be allowed.

Seat

A seat is a collection of sessions and a set of hardware (usually at least a keyboard and mouse). Only one session may be active on a seat at a time.

At the present time, all Sessions that are considered "local" to a system will be added the the first Seat and every other Session will be added to its own Seat.

True, hardware, multi-seat capabilities will be added in a later release.

Chapter 3. Design

Table of Contents

Session Lifecycle

Expected Usage

Text Login Manager
Graphical Login Manager
System Daemon
Hardware Abstraction Layer
Fast User Switching Agent
Session Daemon (aka Policy Agent)
Session Application

Session Lifecycle

The session leader process is responsible for asking ConsoleKit to open a new session. In this respect, it is similar to the traditional POSIX user login accounting framework. In the typical case, the session leader is either an immediate descendant of a login manager or the login manager itself. The leader makes a connection to the D-Bus system bus and asks ConsoleKit to open a session. There are two methods available for opening a session: org.freedesktop.ConsoleKit.Manager.OpenSession() and org.freedesktop.ConsoleKit.Manager.OpenSessionWithParameters().

If the operation succeeds, a secret cookie will be returned to the session leader. The session leader should store this secret in the environment as XDG_SESSION_COOKIE so that it may be shared with its child processes.

At this point the session will be registered with ConsoleKit and a particular set of information about the session will be stored along with it.

ConsoleKit will decide, based on the information associated with the session, what Seat the session will be added to.

It will also be determined, based on the same set of information, whether the Session will control the hardware associated with the Seat. In other words, whether the Session will be active for the Seat it is attached to. The exact mechanism for this determination depends on the type of Seat and the capabilities of the host system.

The Session will remain open until the Session Leader disconnects from the D-Bus system bus or calls org.freedesktop.ConsoleKit.Manager.CloseSession(). The session will be removed from its Seat, and deregistered.

Expected Usage

Use of this service will usually follow one of the following patterns:

Text Login Manager

This pattern operates as the Session Leader for a new Session. This pattern needs:

To open a new Session.
To set properties for the Session.
To maintain a connection to the D-Bus system bus.
To close the Session at logout.

Graphical Login Manager

In addition to the requirements for the Text Graphical Login Manager, this pattern is typically used to show information about currently open sessions. It needs:

To determine which Seat it is running on.
To know if the current seat supports session switching.
A list of all sessions on the current Seat.
To know which session is active for the current Seat.
To know when the session active state changes.
To know when sessions are added or removed.
Access to the metadata for any open Session.

System Daemon

This is generally a daemon process running outside of a user session as a special user. This pattern needs:

To know if any user sessions are open.
To know if the system is currently being used.

Hardware Abstraction Layer

This is a special case of System Daemon that provides catalogs and control mechanisms for hardware devices. In addition to the requirements of System Daemon, this pattern needs:

To determine what hardware is associated with a Seat.
To determine what Session is active and inactive on a particular Seat.
To know when the session active state changes.
To determine what Session a process belongs to.

Fast User Switching Agent

This is related to the Graphical Login Manager and provides a shortcut to similar functionality. It is usually a tool available in the user session that allows one to quickly switch to another user session. This pattern needs:

To determine which session it is running in.
To determine which Seat it is running on.
To know if the current seat supports session switching.
A list of all sessions on the current Seat.
Which session is active for the current Seat.
To know when the session active state changes.
Access to the metadata for any open Session.
To know when sessions are added or removed.

Session Daemon (aka Policy Agent)

This is typically a daemon running in a user session that acts on policy only when the session is active. This pattern needs:

To determine which session it is running in.
To know when the session active state changes.

Session Application

This is typically an application running in a user session that may alter its behavior when the session active state changes. This pattern needs:

To determine which session it is running in.
To know when the session active state changes.

Part II. Reference

Table of Contents

I. D-Bus API Reference

org.freedesktop.ConsoleKit.Manager — Manager interface
org.freedesktop.ConsoleKit.Seat — Seat interface
org.freedesktop.ConsoleKit.Session — Session interface

D-Bus API Reference

ConsoleKit provides a D-Bus API for programs to obtain information about the users, sessions, and seats that are present on a system.

Please see the other sections of this manual for an introduction to these concepts.

This API is not yet stable and is likely to change in the future.

Table of Contents

org.freedesktop.ConsoleKit.Manager — Manager interface
org.freedesktop.ConsoleKit.Seat — Seat interface
org.freedesktop.ConsoleKit.Session — Session interface

Name

org.freedesktop.ConsoleKit.Manager — Manager interface

Methods

Restart                   ()
CanRestart                (out 'b'     can_restart)
Stop                      ()
CanStop                   (out 'b'     can_stop)
OpenSession               (out 's'     cookie)
OpenSessionWithParameters (in  'a(sv)' parameters,
                           out 's'     cookie)
CloseSession              (in  's'     cookie,
                           out 'b'     result)
GetSeats                  (out 'ao'    seats)
GetSessions               (out 'ao'    sessions)
GetSessionForCookie       (in  's'     cookie,
                           out 'o'     ssid)
GetSessionForUnixProcess  (in  'u'     pid,
                           out 'o'     ssid)
GetCurrentSession         (out 'o'     ssid)
GetSessionsForUnixUser    (in  'u'     uid,
                           out 'ao'    sessions)
GetSessionsForUser        (in  'u'     uid,
                           out 'ao'    sessions)
GetSystemIdleHint         (out 'b'     idle_hint)
GetSystemIdleSinceHint    (out 's'     iso8601_datetime)

Signals

SeatAdded             ('o' sid)
SeatRemoved           ('o' sid)
SystemIdleHintChanged ('b' hint)

Implemented Interfaces

Objects implementing org.freedesktop.ConsoleKit.Manager also implements org.freedesktop.DBus.Introspectable, org.freedesktop.DBus.Properties

Description

Details

Restart ()

Restart ()

This method initiates a request to restart (ie. reboot) the computer system.

CanRestart ()

CanRestart (out 'b' can_restart)

can_restart:

Stop ()

Stop ()

This method initiates a request to stop (ie. shutdown) the computer system.

CanStop ()

CanStop (out 'b' can_stop)

can_stop:

OpenSession ()

OpenSession (out 's' cookie)

This method requests that a new Session be created for the calling process. The properties of this new Session are set automatically from information collected about the calling process.

This new session exists until the calling process disconnects from the system bus or calls CloseSession().

It is the responsibility of the calling process to set the environment variable XDG_SESSION_COOKIE to the value of the returned cookie. This cookie should only be made available to child processes of the caller so that they may be identified as members of this session.

See this simple example:

	DBusError       error;
	DBusMessage    *message;
	DBusMessage    *reply;

	message = dbus_message_new_method_call ("org.freedesktop.ConsoleKit",
						"/org/freedesktop/ConsoleKit/Manager",
						"org.freedesktop.ConsoleKit.Manager",
						"OpenSession");
	if (message == NULL) {
		goto out;
	}

        dbus_error_init (&error);
        reply = dbus_connection_send_with_reply_and_block (connector->connection,
                                                           message,
                                                           -1,
                                                           &error);
        if (reply == NULL) {
		goto out;
        }

        dbus_error_init (&error);
        if (! dbus_message_get_args (reply,
                                     &error,
                                     DBUS_TYPE_STRING, &cookie,
                                     DBUS_TYPE_INVALID)) {
		goto out;
        }

cookie:: The secret cookie that is used to identify the new session

OpenSessionWithParameters ()

OpenSessionWithParameters (in  'a(sv)' parameters,
                           out 's'     cookie)

This method requests that a new Session be created for the calling process. The properties of this new Session are from the parameters provided.

This new session exists until the calling process disconnects from the system bus or calls CloseSession().

See the Session properties for a list of valid parameters.

parameters:: An array of sets of property names and values
cookie:: The secret cookie that is used to identify the new session

Permissions

This method is restricted to privileged users by D-Bus policy.

CloseSession ()

CloseSession (in  's' cookie,
              out 'b' result)

This method is used to close the session identified by the supplied cookie.

The session can only be closed by the same process that opened the session.

cookie:: The secret cookie that is used to identify the session
result:: Whether the session was successfully closed

GetSeats ()

GetSeats (out 'ao' seats)

This gets a list of all the Seats that are currently present on the system.

Each Seat ID is an D-Bus object path for the object that implements the Seat interface.

seats:: an array of Seat IDs

GetSessions ()

GetSessions (out 'ao' sessions)

This gets a list of all the Sessions that are currently present on the system.

Each Session ID is an D-Bus object path for the object that implements the Session interface.

sessions:: an array of Session IDs

GetSessionForCookie ()

GetSessionForCookie (in  's' cookie,
                     out 'o' ssid)

Returns the session ID that is associated with the specified cookie.

cookie:: The secret cookie that is used to identify the session
ssid:: The object identifier for the current session

GetSessionForUnixProcess ()

GetSessionForUnixProcess (in  'u' pid,
                          out 'o' ssid)

Attempts to determine the session ID for the specified POSIX process ID (pid).

pid:: The POSIX process ID
ssid:: The object identifier for the current session

GetCurrentSession ()

GetCurrentSession (out 'o' ssid)

Attempts to determine the session ID that the caller belongs to.

See this example of using dbus-send:

  dbus-send --system --dest=org.freedesktop.ConsoleKit \
  --type=method_call --print-reply --reply-timeout=2000 \
  /org/freedesktop/ConsoleKit/Manager \
  org.freedesktop.ConsoleKit.Manager.GetCurrentSession

ssid:: The object identifier for the current session

GetSessionsForUnixUser ()

GetSessionsForUnixUser (in  'u'  uid,
                        out 'ao' sessions)

This gets a list of all the Sessions that are currently open for the specified user.

Each Session ID is an D-Bus object path for the object that implements the Session interface.

uid:: POSIX User identification
sessions:: an array of Session IDs

GetSessionsForUser ()

GetSessionsForUser (in  'u'  uid,
                    out 'ao' sessions)

This gets a list of all the Sessions that are currently open for the specified user.

Each Session ID is an D-Bus object path for the object that implements the Session interface.

uid:: User identification
sessions:: an array of Session IDs

Warning

GetSessionsForUser is deprecated since version 0.1.3 and should not be used in newly-written code. Use GetSessionsForUnixUser instead.

GetSystemIdleHint ()

GetSystemIdleHint (out 'b' idle_hint)

Returns TRUE if the idle-hint property of every open session is TRUE or if there are no open sessions.

idle_hint:: The value of the system-idle-hint

GetSystemIdleSinceHint ()

GetSystemIdleSinceHint (out 's' iso8601_datetime)

Returns an ISO 8601 date-time string that corresponds to the time of the last change of the system-idle-hint.

iso8601_datetime:: An ISO 8601 format date-type string

Signal Details

The SeatAdded signal

SeatAdded ('o' sid)

Emitted when a Seat has been added to the system.

sid:: The Seat ID for the added seat

The SeatRemoved signal

SeatRemoved ('o' sid)

Emitted when a Seat has been removed from the system.

sid:: The Seat ID for the removed seat

The SystemIdleHintChanged signal

SystemIdleHintChanged ('b' hint)

Emitted when the value of the system-idle-hint has changed.

hint:: The value of the system-idle-hint

Name

org.freedesktop.ConsoleKit.Seat — Seat interface

Methods

GetId               (out 'o'     sid)
GetSessions         (out 'ao'    sessions)
GetDevices          (out 'a(ss)' devices)
GetActiveSession    (out 'o'     ssid)
CanActivateSessions (out 'b'     can_activate)
ActivateSession     (in  'o'     ssid)

Signals

ActiveSessionChanged ('o'    ssid)
SessionAdded         ('o'    ssid)
SessionRemoved       ('o'    ssid)
DeviceAdded          ('(ss)' device)
DeviceRemoved        ('(ss)' device)

Implemented Interfaces

Objects implementing org.freedesktop.ConsoleKit.Seat also implements org.freedesktop.DBus.Introspectable, org.freedesktop.DBus.Properties

Description

A seat is a collection of sessions and a set of hardware (usually at least a keyboard and mouse). Only one session may be active on a seat at a time.

Details

GetId ()

GetId (out 'o' sid)

Returns the ID for Seat.

sid:: Seat ID

GetSessions ()

GetSessions (out 'ao' sessions)

This gets a list of all the Sessions that are currently attached to this seat.

Each Session ID is an D-Bus object path for the object that implements the Session interface.

sessions:: an array of Session IDs

GetDevices ()

GetDevices (out 'a(ss)' devices)

This gets a list of all the devices that are currently associated with this seat.

Each device is an D-Bus structure that represents the device type and the device id.

devices:: an array of devices

GetActiveSession ()

GetActiveSession (out 'o' ssid)

Gets the Session ID that is currently active on this Seat.

Returns NULL if there is no active session.

ssid:: Session ID

CanActivateSessions ()

CanActivateSessions (out 'b' can_activate)

Used to determine whether the seat supports session activation.

can_activate:: TRUE if seat supports session activation

ActivateSession ()

ActivateSession (in  'o' ssid)

Attempt to activate the specified session. In most cases, if successful, this will cause the session to become visible and take control of the hardware that is associated with this seat.

ssid:: Session ID

Signal Details

The ActiveSessionChanged signal

ActiveSessionChanged ('o' ssid)

Emitted when the active session has changed.

ssid:: Session ID

The SessionAdded signal

SessionAdded ('o' ssid)

Emitted when a session has been added to the seat.

ssid:: Session ID

The SessionRemoved signal

SessionRemoved ('o' ssid)

Emitted when a session has been removed from the seat.

ssid:: Session ID

The DeviceAdded signal

DeviceAdded ('(ss)' device)

Emitted when a device has been associated with the seat.

device:: Device structure

The DeviceRemoved signal

DeviceRemoved ('(ss)' device)

Emitted when a device has been dissociated from the seat.

device:: Device structure

Name

org.freedesktop.ConsoleKit.Session — Session interface

Methods

GetId               (out 'o' ssid)
GetSeatId           (out 'o' sid)
GetSessionType      (out 's' type)
GetUser             (out 'u' uid)
GetUnixUser         (out 'u' uid)
GetX11Display       (out 's' display)
GetX11DisplayDevice (out 's' x11_display_device)
GetDisplayDevice    (out 's' display_device)
GetRemoteHostName   (out 's' remote_host_name)
GetLoginSessionId   (out 's' login_session_id)
IsActive            (out 'b' active)
IsLocal             (out 'b' local)
GetCreationTime     (out 's' iso8601_datetime)
Activate            ()
Lock                ()
Unlock              ()
GetIdleHint         (out 'b' idle_hint)
GetIdleSinceHint    (out 's' iso8601_datetime)
SetIdleHint         (in  'b' idle_hint)

Signals

ActiveChanged   ('b' is_active)
IdleHintChanged ('b' hint)
Lock            ()
Unlock          ()

Implemented Interfaces

Objects implementing org.freedesktop.ConsoleKit.Session also implements org.freedesktop.DBus.Introspectable, org.freedesktop.DBus.Properties

Properties

'unix-user'          readwrite 'u'
'user'               readwrite 'u'
'session-type'       readwrite 's'
'remote-host-name'   readwrite 's'
'display-device'     readwrite 's'
'x11-display'        readwrite 's'
'x11-display-device' readwrite 's'
'active'             readwrite 'b'
'is-local'           readwrite 'b'
'idle-hint'          readwrite 'b'

Description

Session objects represent and store information related to a user session.

The properties associated with the Session specifically refer to the properties of the "session leader".

Details

GetId ()

GetId (out 'o' ssid)

Returns the ID for Session.

ssid:: Session ID

GetSeatId ()

GetSeatId (out 'o' sid)

Returns the ID for the Seat the Session is attached to.

sid:: Seat ID

GetSessionType ()

GetSessionType (out 's' type)

Returns the type of the session.

Warning: we haven't yet defined the allowed values for this property. It is probably best to avoid this until we do.

type:: Session type

GetUser ()

GetUser (out 'u' uid)

Returns the user that the session belongs to.

uid:: User ID

Warning

GetUser is deprecated since version 0.1.3 and should not be used in newly-written code. Use GetUnixUser instead.

GetUnixUser ()

GetUnixUser (out 'u' uid)

Returns the POSIX user ID that the session belongs to.

uid:: POSIX User ID

GetX11Display ()

GetX11Display (out 's' display)

Returns the value of the X11 DISPLAY for this session if one is present.

display:: The value of the X11 display

GetX11DisplayDevice ()

GetX11DisplayDevice (out 's' x11_display_device)

Returns the value of the display device (aka TTY) that the X11 display for the session is connected to. If there is no x11-display set then this value is undefined.

x11_display_device:: The value of the X11 display device

GetDisplayDevice ()

GetDisplayDevice (out 's' display_device)

Returns the value of the display device (aka TTY) that the session is connected to.

display_device:: The value of the display device

GetRemoteHostName ()

GetRemoteHostName (out 's' remote_host_name)

Returns the value of the remote host name for the session.

remote_host_name:: The remote host name

GetLoginSessionId ()

GetLoginSessionId (out 's' login_session_id)

Returns the value of the login session ID that the underlying system uses to enforce session boundaries. If there is no login session ID set then this value is an empty string.

login_session_id:: The value of the native system login session ID

IsActive ()

IsActive (out 'b' active)

Returns whether the session is active on the Seat that it is attached to.

If the session is not attached to a seat this value is undefined.

active:: TRUE if the session is active, otherwise FALSE

IsLocal ()

IsLocal (out 'b' local)

Returns whether the session is local

FIXME: we need to come up with a concrete definition for this value. It was originally used as a way to identify XDMCP sessions that originate from a remote system.

local:: TRUE if the session is local, otherwise FALSE

GetCreationTime ()

GetCreationTime (out 's' iso8601_datetime)

Returns an ISO 8601 date-time string that corresponds to the time that the session was opened.

iso8601_datetime:: An ISO 8601 format date-type string

Activate ()

Activate ()

Attempt to activate the this session. In most cases, if successful, this will cause the session to become visible and become active on the seat that it is attached to.

Lock ()

Lock ()

This will cause a Lock signal to be emitted for this session.

Permissions

This method is restricted to privileged users by D-Bus policy.

Unlock ()

Unlock ()

This will cause an Unlock signal to be emitted for this session.

This can be used by login managers to unlock a session before it is re-activated during fast-user-switching.

Permissions

This method is restricted to privileged users by D-Bus policy.

GetIdleHint ()

GetIdleHint (out 'b' idle_hint)

Gets the value of the idle-hint property.

idle_hint:: The value of the idle-hint

GetIdleSinceHint ()

GetIdleSinceHint (out 's' iso8601_datetime)

Returns an ISO 8601 date-time string that corresponds to the time of the last change of the idle-hint.

iso8601_datetime:: An ISO 8601 format date-type string

SetIdleHint ()

SetIdleHint (in  'b' idle_hint)

This may be used by the session to indicate that it is idle.

Use of this method is restricted to the user that owns the session.

idle_hint:: boolean value to set the idle-hint to

Signal Details

The ActiveChanged signal

ActiveChanged ('b' is_active)

Emitted when the active property has changed.

is_active:: TRUE if the session is active, otherwise FALSE

The IdleHintChanged signal

IdleHintChanged ('b' hint)

Emitted when the idle-hint property has changed.

hint:: the new value of idle-hint

The Lock signal

Lock ()

Emitted in response to a call to the Lock() method.

It is intended that the screensaver for the session should lock the screen in response to this signal.

The Unlock signal

Unlock ()

Emitted in response to a call to the Unlock() method.

It is intended that the screensaver for the session should unlock the screen in response to this signal.

Property Details

The "unix-user" property

'unix-user'  readwrite 'u'

The user assigned to the session.

The "user" property

'user'  readwrite 'u'

The user assigned to the session.

Warning

user is deprecated since version 0.1.3 and should not be used in newly-written code. Use unix-user instead.

The "session-type" property

'session-type'  readwrite 's'

The type of the session.

Warning: we haven't yet defined the allowed values for this property. It is probably best to avoid this until we do.

The "remote-host-name" property

'remote-host-name'  readwrite 's'

The remote host name for the session.

This will be set in situations where the session is opened and controlled from a remote system.

For example, this value will be set when the session is created from an SSH or XDMCP connection.

The "display-device" property

'display-device'  readwrite 's'

The display device (aka TTY) that the session is connected to.

The "x11-display" property

'x11-display'  readwrite 's'

Value of the X11 DISPLAY for this session if one is present.

The "x11-display-device" property

'x11-display-device'  readwrite 's'

The display device (aka TTY) that the X11 display for the session is connected to. If there is no x11-display set then this value is undefined.

The "active" property

'active'  readwrite 'b'

Whether the session is active on the Seat that it is attached to.

If the session is not attached to a seat this value is undefined.

The "is-local" property

'is-local'  readwrite 'b'

Whether the session is local

FIXME: we need to come up with a concrete definition for this value. It was originally used as a way to identify XDMCP sessions that originate from a remote system.

The "idle-hint" property

'idle-hint'  readwrite 'b'

This is a hint used to indicate that the session may be idle.

For sessions with a x11-display set (ie. graphical sessions), it is up to each session to delegate the responsibility for updating this value. Typically, the screensaver will set this.

However, for non-graphical sessions with a display-device set the Session object itself will periodically update this value based on the activity detected on the display-device itself.

This should not be considered authoritative.