демон сборщика показателей производительности (performance metrics collector daemon)
STARTING AND STOPPING PMCD
Normally, pmcd is started automatically at boot time and stopped
when the system is being brought down. Under certain
circumstances it is necessary to start or stop pmcd manually. To
do this one must become superuser and type
# $PCP_RC_DIR/pmcd start
to start pmcd, or
# $PCP_RC_DIR/pmcd stop
to stop pmcd. Starting pmcd when it is already running is the
same as stopping it and then starting it again.
Sometimes it may be necessary to restart pmcd during another
phase of the boot process. Time-consuming parts of the boot
process are often put into the background to allow the system to
become available sooner (e.g. mounting huge databases). If an
agent run by pmcd requires such a task to complete before it can
run properly, it is necessary to restart or reconfigure pmcd
after the task completes. Consider, for example, the case of
mounting a database in the background while booting. If the PMDA
which provides the metrics about the database cannot function
until the database is mounted and available but pmcd is started
before the database is ready, the PMDA will fail (however pmcd
will still service requests for metrics from other domains). If
the database is initialized by running a shell script, adding a
line to the end of the script to reconfigure pmcd (by sending it
a SIGHUP) will restart the PMDA (if it exited because it couldn't
connect to the database). If the PMDA didn't exit in such a
situation it would be necessary to restart pmcd because if the
PMDA was still running pmcd would not restart it.
Normally pmcd listens for client connections on TCP/IP port
number 44321 (registered at http://www.iana.org/ ). Either the
environment variable PMCD_PORT or the -p command line option may
be used to specify alternative port number(s) when pmcd is
started; in each case, the specification is a comma-separated
list of one or more numerical port numbers. Should both methods
be used or multiple -p options appear on the command line, pmcd
will listen on the union of the set of ports specified via all -p
options and the PMCD_PORT environment variable. If non-default
ports are used with pmcd care should be taken to ensure that
PMCD_PORT is also set in the environment of any client
application that will connect to pmcd, or that the extended host
specification syntax is used (see PCPIntro(1) for details).
