NAME
sge_commd - Grid Engine communication agent
SYNOPSIS
sge_commd [ -S ] [ -a aliasfile ] [ -dhr ] [ -help ] [ -ll
loglevel ] [ -ml fname ] [ -nd ] [ -p port ] [ -s service ]
DESCRIPTION
All network communication in a Grid Engine cluster is per-
formed via the communication daemons sge_commd. Client pro-
grams like qsub(1) or qstat(1) as well as Grid Engine dae-
mons such as sge_qmaster(8) or sge_execd(8) use the service
provided by sge_commd in order to send/receive messages
to/from other Grid Engine components.
sge_commd handles an arbitrary number of concurrent synchro-
nous or asynchronous communications. Usually one sge_commd
is started up automatically on each host on which
sge_qmaster(8), sge_execd(8) or/and sge_schedd(8) are
invoked. It is however possible to connect multiple hosts
via one sge_commd or to use a sge_commd on a submit or
administrative Grid Engine host (without running one of the
other Grid Engine daemons) as communication agent for the
Grid Engine client programs invoked from that host.
OPTIONS
-S Forces secure ports to be used for communication
between sge_commds and between other Grid Engine com-
ponents and the sge_commds. This requires all Grid
Engine daemons to be started with root permission and
the client programs to be configured set-uid root. In
turn, it ensures that unauthorized communication is
prohibited for non-root accounts.
-a aliasfile
A file containing Grid Engine host aliases used by the
sge_commd to resolve Grid Engine unique hostnames for
all hosts in the cluster. The hostname resolving ser-
vice of sge_commd is also used by all other Grid Engine
components. The file format and the implication of its
usage are described in sge_h_aliases(5).
-dhr The hostname resolving C-library functions (such as
gethostent(3), gethostbyname(3) and gethostbyaddr(3))
perform some kind of caching on some OS architectures.
Network wide hostname databases distributed by services
such as DNS (Domain Name Service) and NIS (Network
Information Service) are updated with a delay of
several minutes. This only affects applications which
repeatedly resolve hostnames (such as sge_commd). At
start-up of a program the most recent information is
accessed, thus commands like telnet(1) or nslookup(1)
are not affected.
However, for sge_commd it makes no sense to resolve
hostnames anytime (the returned information may be out
of date anyway) and resolving can be an expensive
operation if the network is overloaded and/or NIS or
DNS servers are very busy. Therefore, sge_commd
resolves hostname information from time to time only.
Yet, if hostname resolving still causes problems due to
network load, for example, it can be turned off with
the -dhr switch. The administrator has to be aware,
that if the hostname resolving is turned off, sge_commd
has to be restarted as soon as the hostname databases
change significantly.
-help
Prints a listing of all options.
-ll loglevel
Sets a logging level for error tracing. The error trace
information is written to the file
/tmp/commd/err.<pid>. However, the directory /tmp/commd
must be present, otherwise the tracing output is dis-
carded. At present, 255 is the only valid logging
level.
-nd Do not daemonize. If started with -nd, sge_commd main-
tains its connection to the controlling terminal and
thus outputs trace information directly to the terminal
from which sge_commd was invoked. The trace information
is the same as being accessible via the -ll option (see
above).
-p port_number
Use this TCP port for communication with other commds.
-s service_name
Use this service name and thus the associated TCP port
for communication with other commds.
ENVIRONMENTAL VARIABLES
SGE_ROOT Specifies the location of the Grid Engine
standard configuration files.
COMMD_PORT If set, specifies the tcp port on which
sge_commd is expected to listen for communi-
cation requests. Most installations will use
a services map entry instead to define that
port.
COMMD_HOST (Does not affect the behavior of sge_commd
but of the other Grid Engine components con-
tacting sge_commd.) If set, specifies the
host on which the particular sge_commd to be
used for Grid Engine communication of arbi-
trary Grid Engine client programs or daemons
resides. Per default the local host is used.
RESTRICTIONS
sge_commd usually is invoked by a starting sge_qmaster(8)
and sge_execd(8) and thus is running under root permission.
If started by a normal user the -S switch may not be used as
the secure mode requires root permission (see above).
SEE ALSO
sge_intro(1), sge_h_aliases(5), sge_execd(8),
sge_qmaster(8), commdcntl(8).
COPYRIGHT
See sge_intro(1) for a full statement of rights and permis-
sions.
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