Most MPI users will probably not need to use the
doom
command; see lamboot(1).
The
hboot
tool
can be understood as a generic utility that starts multiple processes
on the local node, based on information in a process schema.
It is not restricted to starting LAM.
It is part of the startup sequence preformed by lamboot(1).
A process schema is a description of the processes which constitute
the operating system on a given node.
Naturally, the process schema used by
hboot
should be the one that describes LAM on a node.
The grammar of the process schema is described in conf(5).
When starting LAM on a remote machine using rsh(1), the open file
descriptors of the processes started by
hboot
must be closed in order for rsh(1) to exit.
This is done by using the
-s
option.
The
-t
option can be used to force a tkill(1) on the machine before attempting
to start LAM.
This feature is used by lamboot(1) to handle the case where
a user might start a machine a second time without using wipe(1) to
terminate the previous LAM session.
The -I and -R options set their
respective variables to the given values.
The $inet_topo variable is typically used by the LAM Internet datalinks
that communicate with other nodes.
The $rtr_topo variable is passed to the LAM router that
handles network and topology information.
The variables can also be set in the process schema file (see conf(5))
but their values are overridden by the command line options.
When LAM is started, the kernel records all processes that
attach to it, including all the processes in the process schema.
It is the job of tkill(1)
to use this information to remove these processes from the node.