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Table of Contents
xsm - X Session Manager
xsm [-display
display] [-session sessionName] [-verbose]
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.
- -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.
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).
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.
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 exists, 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>
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 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.
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.
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.
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.
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.
smproxy(1)
, rstart(1)
Ralph
Mor, X Consortium
Jordan Brown, Quarterdeck Office Systems
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