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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 <I>sge</I>_<I>commd</I>. Client pro-
grams like <B><A HREF="../htmlman1/qsub.html">qsub(1)</A></B> or <B><A HREF="../htmlman1/qstat.html">qstat(1)</A></B> as well as Grid Engine dae-
mons such as <B><A HREF="../htmlman8/sge_qmaster.html">sge_qmaster(8)</A></B> or <B><A HREF="../htmlman8/sge_execd.html">sge_execd(8)</A></B> use the service
provided by <I>sge</I>_<I>commd</I> in order to send/receive messages
to/from other Grid Engine components.
<I>sge</I>_<I>commd</I> handles an arbitrary number of concurrent synchro-
nous or asynchronous communications. Usually one <I>sge</I>_<I>commd</I>
is started up automatically on each host on which
<B><A HREF="../htmlman8/sge_qmaster.html">sge_qmaster(8)</A></B>, <B><A HREF="../htmlman8/sge_execd.html">sge_execd(8)</A></B> or/and <B><A HREF="../htmlman8/sge_schedd.html">sge_schedd(8)</A></B> are
invoked. It is however possible to connect multiple hosts
via one <I>sge</I>_<I>commd</I> or to use a <I>sge</I>_<I>commd</I> 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 <I>sge</I>_<I>commd</I>s and between other Grid Engine com-
ponents and the <I>sge</I>_<I>commd</I>s. 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
<I>sge</I>_<I>commd</I> to resolve Grid Engine unique hostnames for
all hosts in the cluster. Overrides the usage of the
default host_aliases file under
<<I>sge</I>_<I>root</I>>/<<I>cell</I>>/<I>common</I>/<I>host</I>_<I>aliases</I>. The hostname
resolving service of <I>sge</I>_<I>commd</I> is also used by all
other Grid Engine components. The file format and the
implication of its usage are described in
<B><A HREF="../htmlman5/sge_h_aliases.html">sge_h_aliases(5)</A></B>.
-dhr The hostname resolving C-library functions (such as
<B><A HREF="../htmlman3/gethostent.html">gethostent(3)</A></B>, <B><A HREF="../htmlman3/gethostbyname.html">gethostbyname(3)</A></B> and <B><A HREF="../htmlman3/gethostbyaddr.html">gethostbyaddr(3)</A></B>)
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 <I>sge</I>_<I>commd</I>). At
start-up of a program the most recent information is
accessed, thus commands like <B><A HREF="../htmlman1/telnet.html">telnet(1)</A></B> or <B><A HREF="../htmlman1/nslookup.html">nslookup(1)</A></B>
are not affected.
However, for <I>sge</I>_<I>commd</I> 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, <I>sge</I>_<I>commd</I>
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, <I>sge</I>_<I>commd</I>
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
/<I>tmp</I>/<I>commd</I>/<I>err</I>.<<I>pid</I>>. However, the directory /<I>tmp</I>/<I>commd</I>
must be present, otherwise the tracing output is dis-
carded. At present, 255 is the only valid logging
level.
-ml fname
Enables message logging to file.
-nd Do not daemonize. If started with -nd, <I>sge</I>_<I>commd</I> main-
tains its connection to the controlling terminal and
thus outputs trace information directly to the terminal
from which <I>sge</I>_<I>commd</I> 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
<I>sge</I>_<I>commd</I> 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 <I>sge</I>_<I>commd</I>
but of the other Grid Engine components con-
tacting <I>sge</I>_<I>commd</I>.) If set, specifies the
host on which the particular <I>sge</I>_<I>commd</I> 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
<I>sge</I>_<I>commd</I> usually is invoked by a starting <B><A HREF="../htmlman8/sge_qmaster.html">sge_qmaster(8)</A></B>
and <B><A HREF="../htmlman8/sge_execd.html">sge_execd(8)</A></B> 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
<B><A HREF="../htmlman1/sge_intro.html">sge_intro(1)</A></B>, <B><A HREF="../htmlman5/sge_h_aliases.html">sge_h_aliases(5)</A></B>, <B><A HREF="../htmlman8/sge_execd.html">sge_execd(8)</A></B>,
<B><A HREF="../htmlman8/sge_qmaster.html">sge_qmaster(8)</A></B>, <B><A HREF="../htmlman8/commdcntl.html">commdcntl(8)</A></B>.
COPYRIGHT
See <B><A HREF="../htmlman1/sge_intro.html">sge_intro(1)</A></B> for a full statement of rights and permis-
sions.
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