NAME
xsm - X Session Manager

SYNOPSIS
xsm [-display display] [-session sessionName] [-verbose]

DESCRIPTION
xsm is a session manager. A session is a group of applica-
tions, 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 gen-
eral, 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 check-
point 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 exists, it
will look for the system.xsm file that was set up at instal-
lation 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 pre-
viously 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. Alterna-
tively, hitting the Return key will
also load the currently selected ses-
sion, 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 ses-
sion, 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 run-
ning 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 Res-
tart 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 addi-
tion, the client is meant to run continu-
ously. 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 manu-
ally add such applications to the session.
The bottom of the Client List window con-
tains a text entry field in which applica-
tion commands can be typed in. Each com-
mand 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 reg-
ular "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 exam-
ple, when a session is restarted, all of
the restart commands will be displayed in
the log window.

Checkpoint By performing a checkpoint, all applica-
tions 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 configura-
tions.

If the session being checkpointed was
never assigned a name, the user will be
required to specify a session name. Oth-
erwise, the user can perform the check-
point 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 applica-
tion 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 appli-
cation 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 applica-
tion should do both of these. For exam-
ple, 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 applica-
tion should not interact with the user
while saving state.

The Errors type indicates that the appli-
cation may interact with the user only if
an error condition arises.

The Any type indicates that the applica-
tion 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 con-
taining 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 ses-
sion with our without performing a check-
point.

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.