Provided by: x11-session-utils_7.7+2build1_amd64 
NAME
xsm - X Session Manager
SYNOPSIS
xsm [-display display] [-session sessionName] [-verbose]
DESCRIPTION
xsm 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 of xsm, however, can be taken advantage of when more
and more applications learn to save and restore their state.
OPTIONS
-display display
Causes xsm to connect to the specified X display.
-session sessionName
Causes xsm to load the specified session, bypassing the session menu.
-verbose
Turns on debugging information.
SETUP
.xsession file
Using xsm requires a change to your .xsession file:
The last program executed by your .xsession file should be xsm. With this configuration, when the user
chooses to shut down the session using xsm, 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. When xsm 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 will save 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>
twm
smproxy
xterm
<end of file>
STARTING A SESSION
When xsm 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 Startup Applications). 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
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 the list.
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.
Cancel Pressing this button will cause xsm to exit. It can also be used to cancel a
"Delete Session" operation.
CONTROLLING A SESSION
After xsm 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 selected application.
By pressing the Kill Client button, the user can remove a client from the session.
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 is terminated.
- 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 current session.
- 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" applications.
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.
Checkpoint 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 overwritten.
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 Style.
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.
Shutdown 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 checkpoint.
HOW XSM RESPONDS TO SIGNALS
xsm 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.
xsm 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.
THE PROXY
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, WM_NAME, WM_COMMAND, and
WM_CLIENT_MACHINE properties.
or ...
- The application maps a top level window which does not contain the WM_CLIENT_LEADER property. However,
this top level window contains the WM_CLASS, WM_NAME, WM_COMMAND, and WM_CLIENT_MACHINE properties.
An application that support the WM_SAVE_YOURSELF protocol will receive a WM_SAVE_YOURSELF 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.
REMOTE APPLICATIONS
xsm requires a remote execution protocol in order to restart applications on remote machines. Currently,
xsm supports the rstart protocol. In order to restart an application on remote machine X, machine X must
have rstart installed. In the future, additional remote execution protocols may be supported.
SEE ALSO
smproxy(1), rstart(1)
AUTHORS
Ralph Mor, X Consortium
Jordan Brown, Quarterdeck Office Systems