xsm - X Session Manager
[-display display] [-session sessionName] [-verbose]
is a session manager. A session is a group of applications, each of
which has a particular state. xsm
allows you to create arbitrary
sessions - for example, you might have a "light" session, a
"development" session, or an "xterminal" session. Each
session can have its own set of applications. Within a session, you can
perform a "checkpoint" to save application state, or a
"shutdown" to save state and exit the session. When you log back in
to the system, you can load a specific session, and you can delete sessions
you no longer want to keep.
Some session managers simply allow you to manually specify a list of
applications to be started in a session. xsm
is more powerful because
it lets you run applications and have them automatically become part of the
session. On a simple level, xsm
is useful because it gives you this
ability to easily define which applications are in a session. The true power
, however, can be taken advantage of when more and more
applications learn to save and restore their state.
- -display display
- Causes xsm to connect to the specified X
- -session sessionName
- Causes xsm to load the specified session, bypassing
the session menu.
- Turns on debugging information.
requires a change to your .xsession
The last program executed by your .xsession
file should be xsm
With this configuration, when the user chooses to shut down the session using
, the session will truly be over.
Since the goal of the session manager is to restart clients when logging into a
session, your .xsession file, in general, should not directly start up
applications. Rather, the applications should be started within a session.
shuts down the session, xsm
will know to restart these
applications. Note however that there are some types of applications that are
not "session aware". xsm
allows you to manually add these
applications to your session (see the section titled Client List
SM_SAVE_DIR environment variable¶
If the SM_SAVE_DIR
environment variable is defined, xsm
all configuration files in this directory. Otherwise, they will be stored in
the user's home directory. Session aware applications are also encouraged to
save their checkpoint files in the SM_SAVE_DIR
directory, although the
user should not depend on this convention.
Default Startup Applications¶
The first time xsm
is started, it will need to locate a list of
applications to start up. For example, this list might include a window
manager, a session management proxy, and an xterm. xsm
will first look
for the file .xsmstartup
in the user's home directory. If that file
does not exist, it will look for the system.xsm
file that was set up at
installation time. Note that xsm
provides a "fail safe"
option when the user chooses a session to start up. The fail safe option
simply loads the default applications described above.
Each line in the startup file should contain a command to start an application.
A sample startup file might look this:
<start of file>
<end of file>
STARTING A SESSION¶
starts up, it first checks to see if the user previously saved
any sessions. If no saved sessions exist, xsm
starts up a set of
default applications (as described above in the section titled Default
). If at least one session exists, a session menu is
presented. The [-session sessionName]
option forces the specified
session to be loaded, bypassing the session menu.
The session menu presents the user with a list of sessions to choose from. The
user can change the currently selected session with the mouse, or by using the
up and down arrows on the keyboard. Note that sessions which are locked (i.e.
running on a different display) can not be loaded or deleted.
The following operations can be performed from the session menu:
- Load Session
- Pressing this button will load the currently selected
session. Alternatively, hitting the Return key will also load the
currently selected session, or the user can double click a session from
- Delete Session
- This operation will delete the currently selected session,
along with all of the application checkpoint files associated with the
session. After pressing this button, the user will be asked to press the
button a second time in order to confirm the operation.
- Default/Fail Safe
- xsm will start up a set of default applications (as
described above in the section titled Default Startup
Applications). This is useful when the user wants to start a fresh
session, or if the session configuration files were corrupted and the user
wants a "fail safe" session.
- Pressing this button will cause xsm to exit. It can
also be used to cancel a "Delete Session" operation.
CONTROLLING A SESSION¶
determines which session to load, it brings up its main window,
then starts up all applications that are part of the session. The title bar
for the session manager's main window will contain the name of the session
that was loaded.
The following options are available from xsm
's main window:
- Client List
- Pressing this button brings up a window containing a list
of all clients that are in the current session. For each client, the host
machine that the client is running on is presented. As clients are added
and removed from the session, this list is updated to reflect the changes.
The user is able to control how these clients are restarted (see below).
By pressing the View Properties button, the user can view the session
management properties associated with the currently selected client.
By pressing the Clone button, the user can start a copy of the
By pressing the Kill Client button, the user can remove a client from
By selecting a restart hint from the Restart Hint menu, the user can
control the restarting of a client. The following hints are available:
- The Restart If Running hint indicates that the client should
be restarted in the next session if it is connected to the session manager
at the end of the current session.
- The Restart Anyway hint indicates that the client should be
restarted in the next session even if it exits before the current session
- The Restart Immediately hint is similar to the Restart
Anyway hint, but in addition, the client is meant to run continuously.
If the client exits, the session manager will try to restart it in the
- The Restart Never hint indicates that the client should not
be restarted in the next session.
Note that all X applications may not be "session aware".
Applications that are not session aware are ones that do not support the X
Session Management Protocol or they can not be detected by the Session
Management Proxy (see the section titled THE PROXY). xsm
allows the user to manually add such applications to the session. The
bottom of the Client List window contains a text entry field in
which application commands can be typed in. Each command should go on its
own line. This information will be saved with the session at checkpoint or
shutdown time. When the session is restarted, xsm will restart
these applications in addition to the regular "session aware"
Pressing the Done button removes the Client List window.
- Session Log...
- The Session Log window presents useful information about
the session. For example, when a session is restarted, all of the restart
commands will be displayed in the log window.
- By performing a checkpoint, all applications that are in
the session are asked to save their state. Not every application will save
its complete state, but at a minimum, the session manager is guaranteed
that it will receive the command required to restart the application
(along with all command line options). A window manager participating in
the session should guarantee that the applications will come back up with
the same window configurations.
If the session being checkpointed was never assigned a name, the user will
be required to specify a session name. Otherwise, the user can perform the
checkpoint using the current session name, or a new session name can be
specified. If the session name specified already exists, the user will be
given the opportunity to specify a different name or to overwrite the
already existing session. Note that a session which is locked can not be
When performing a checkpoint, the user must specify a Save Type which
informs the applications in the session how much state they should save.
The Local type indicates that the application should save enough
information to restore the state as seen by the user. It should not affect
the state as seen by other users. For example, an editor would create a
temporary file containing the contents of its editing buffer, the location
of the cursor, etc...
The Global type indicates that the application should commit all of
its data to permanent, globally accessible storage. For example, the
editor would simply save the edited file.
The Both type indicates that the application should do both of these.
For example, the editor would save the edited file, then create a
temporary file with information such as the location of the cursor, etc...
In addition to the Save Type, the user must specify an Interact
The None type indicates that the application should not interact with
the user while saving state.
The Errors type indicates that the application may interact with the
user only if an error condition arises.
The Any type indicates that the application may interact with the
user for any purpose. Note that xsm will only allow one application
to interact with the user at a time.
After the checkpoint is completed, xsm will, if necessary, display a
window containing the list of applications which did not report a
successful save of state.
- A shutdown provides all of the options found in a
checkpoint, but in addition, can cause the session to exit. Note that if
the interaction style is Errors or Any, the user may cancel
the shutdown. The user may also cancel the shutdown if any of the
applications report an unsuccessful save of state.
The user may choose to shutdown the session with our without performing a
HOW XSM RESPONDS TO SIGNALS¶
will respond to a SIGTERM signal by performing a shutdown with the
following options: fast, no interaction, save type local. This allows the
user's session to be saved when the system is being shutdown. It can also be
used to perform a remote shutdown of a session.
will respond to a SIGUSR1 signal by performing a checkpoint with the
following options: no interaction, save type local. This signal can be used to
perform a remote checkpoint of a session.
Since not all applications have been ported to support the X Session Management
Protocol, a proxy service exists to allow "old" clients to work with
the session manager. In order for the proxy to detect an application joining a
session, one of the following must be true:
- The application maps a top level window containing the WM_CLIENT_LEADER
property. This property provides a pointer to the client leader window which
contains the WM_CLASS
- The application maps a top level window which does not contain the
property. However, this top level window contains the
An application that support the WM_SAVE_YOURSELF
protocol will receive a
client message each time the session manager issues a
checkpoint or shutdown. This allows the application to save state. If an
application does not support the WM_SAVE_YOURSELF
protocol, then the
proxy will provide enough information to the session manager to restart the
application (using WM_COMMAND
), but no state will be restored.
requires a remote execution protocol in order to restart applications
on remote machines. Currently, xsm
supports the rstart
In order to restart an application on remote machine X
must have rstart
installed. In the future, additional remote
execution protocols may be supported.
Ralph Mor, X Consortium
Jordan Brown, Quarterdeck Office Systems