xsm
X Session Manager
see also :
smproxy - rstart
Synopsis
xsm
[-display display] [-session sessionName] [-verbose]
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examples
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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.
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.
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.
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.
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.
see also
smproxy ,
rstart
authors
Ralph Mor, X
Consortium
Jordan Brown, Quarterdeck Office Systems