lamshrink - Shrink a LAM multicomputer.
SYNTAX
lamshrink [-hv] [-w <delay>] [-u <userid>] <node>
<hostname>
OPTIONS
-h Print useful information on this command.
-v Be verbose.
<hostname> Remove the LAM node on this host.
<node> Remove the LAM node with this ID.
-w <delay> Notify processes on the doomed node and
pause for <delay> seconds before proceeding.
-u <userid> Use this userid to access the host.
DESCRIPTION
An existing LAM session, initiated by lamboot(1), can be
shrunk to include less nodes with lamshrink. One node is
removed for each invocation. At a minimum, the node ID
and the associated host name is given on the command line.
Once lamshrink completes, the node ID is invalid across
the remaining nodes. If a different userid is required to
access the host, it is specified with the -u option.
Existing application processes on the target node can be
warned of impending shutdown with the -w option. A LAM
signal (SIGFUSE) will be sent to these processes and
lamshrink will then pause for the given number of seconds
before proceeding with removing the node. By default,
SIGFUSE is ignored. A different handler can be installed
with ksignal(2).
All application processes on all remaining nodes are al
ways informed of the death of a node. This is also done
with a signal (SIGSHRINK), which by default causes a pro
cess's runtime route cache to be flushed (to remove any
cached information on the dead node). If this signal is
re-vectored for the purpose of fault tolerance, the old
handler should be called at the beginning of the new han
dler. The signal does not, by itself, give the process
information on which node has been removed. One technique
for getting this information is to query the router for
information on all relevant nodes using getroute(2). The
dead node will cause this routine to return an error.
FAULT TOLERANCE
If enabled with lamboot(1), LAM will watch for nodes that
fail. The procedure for removing a node that has failed
ticular, the SIGSHRINK signal is delivered.
EXAMPLES
lamshrink -v newhost n1
Remove LAM on newhost, known within LAM as node 1.
Report about important steps as they are done.
lamshrink newhost n30 -w 10
Inform all processes on LAM node 30, which is running
on newhost, that the node will be dead in 10 seconds.
Wait 10 seconds and remove the node. Operate silent
ly.
SEE ALSO
lamboot(1), tkill(1), ksignal(2), getroute(2)
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