pmdapipe(1) — Linux manual page


PMDAPIPE(1)              General Commands Manual             PMDAPIPE(1)

NAME         top

       pmdapipe - command output capture performance metrics domain
       agent (PMDA)

SYNOPSIS         top

       $PCP_PMDAS_DIR/pipe/pmdapipe [-c configfile] [-d domain] [-l
       logfile] [-m memory]

DESCRIPTION         top

       pmdapipe is a configurable command output monitoring Performance
       Metrics Domain Agent (PMDA).  It can be seen as analogous to a
       restricted shell, where options can be passed to preset commands,
       and each line of their output is converted into a performance
       event.  These events can be consumed by client tools like

       The pipe PMDA exports both event-style metrics reflecting
       timestamped event records for text-oriented command output, as
       well as the more orthodox sample-style metrics such as event
       counts and throughput size values.

       The PMDA is configured via a configfile which contains one line
       for each process from which output can be captured, as described
       in the ``CONFIGURATION'' section below.

       A brief description of the pmdapipe command line options follows:

       -c   specifies an alternate configuration file for the PMDA.  By
            default, a file named $PCP_PMDAS_DIR/pipe/pipe.conf and any
            files below the $PCP_SYSCONF_DIR/pipe.conf.d/ directory are

       -d   It is absolutely crucial that the performance metrics domain
            number specified here is unique and consistent.  That is,
            domain should be different for every PMDA on the one host,
            and the same domain number should be used for the same PMDA
            on all hosts.

       -l   Location of the log file.  By default, a log file named
            pipe.log is written in the current directory of pmcd(1) when
            pmdapipe is started, i.e.  $PCP_LOG_DIR/pmcd.  If the log
            file cannot be created or is not writable, output is written
            to the standard error instead.

       -m   Limit the physical memory used by the PMDA to buffer event
            records to maxsize bytes.  As log events arrive at the PMDA,
            they must be buffered until individual client tools request
            the next batch since their previous batch of events.  The
            default maximum is 2 megabytes.


       The set of allowed pipe commands is configured by simple text
       file(s).  The format is a single line for each command followed
       by an optional access control section.

       Blank lines and comments are permitted (even encouraged) in the
       configuration file.  A comment begins with a ``#'' character and
       finishes at the end of the line.

       Each command configuration line is of the form:

              instance username command options


              is a string identifying the pipe command, also exported as
              the metric instance identifier.
              is the name of the user account under which the command
              should run (e.g. "root")
              is the path to the binary which will be run to generate
              piped output
              is an optional space-separated list of parameters to pass
              to the command

                     This options list may contain numeric parameters
                     prefixed by the dollar-sign, and these will be
                     substituted with user-supplied values at the time
                     the command is run (similar to shell parameter

       Parameters are passed as a single space-separated or comma-
       separated string to the pipe.firehose metric, using the
       pmStore(3) interface.  The pmval command provides store access
       via its -x option.  User-supplied parameters are restricted to
       containing alphanumeric characters.

       The access control section of the file must start with a line of
       the form:


       Leading and trailing whitespace may appear around and within the
       brackets and the case of the access keyword is ignored.  No other
       text may appear on the line except a trailing comment.

       Following this line, the remainder of the configuration file
       should contain lines that allow or disallow use of commands from
       particular users or groups.

       User names and group names will be verified using the local
       /etc/passwd and /etc/groups files (or an alternative directory
       service), using the getpwent(3) and getgrent(3) routines.

       Access for users or groups are allowed or disallowed by
       specifying statements of the form:

              allow user username : instance
              disallow user username : instance
              allow group groupname : instance
              disallow group groupname : instance

       The username and groupname names will be verified using the local
       /etc/passwd and /etc/groups files (or an alternative directory
       service), using the getpwent(3) and getgrent(3) routines.

       The wildcard ``*'' can be used to refer to all instance names.

INSTALLATION         top

       If you want access to the names, help text and values for the
       pipe performance metrics, do the following as root:

            # cd $PCP_PMDAS_DIR/pipe
            # ./Install

       This is an interactive installation process which prompts for
       each log file path to be monitored (or command to be run), a
       metric instance name to identify it, and whether access should be
       restricted (refer to the -x option to pmval(1) for further

       If you want to undo the installation, do the following as root:

            # cd $PCP_PMDAS_DIR/pipe
            # ./Remove

       pmdapipe is launched by pmcd and should never be executed
       directly.  The Install and Remove scripts notify pmcd when the
       agent is installed or removed.

EXAMPLES         top

       Following is a simple example of pmdapipe configuration and use
       of the pipe metrics to run the btrace command, by user bob:

            bob> cat $PCP_PMDAS_DIR/pipe/pipe.conf
            # instance      user      command
            rw_syscalls     root      perf script rw-by-file $1
            bdev_trace      root      btrace -w $1 /dev/$2

            allow user bob : *;
            allow user jane : bdev_trace;
            allow group perf : rw_syscalls;

            bob> pmval -i bdev_trace -x '5 sda' pipe.firehose
             8,2  5  1  0.000000000 25227  A  WS 734332384 + 24 <- (253,2) 734330336
             8,0  5  2  0.000000414 25227  A  WS 735358432 + 24 <- (8,2) 734332384
             8,0  5  3  0.000000756 25227  Q  WS 735358432 + 24 [qemu-kvm]
             [...5 seconds worth]

FILES         top

              command line options used to launch pmdapipe
              default configuration file for the pipe metrics
              default help text file for the pipe metrics
              installation script for the pmdapipe agent
              undo installation script for the pmdapipe agent
              default log file for error messages and other information
              from pmdapipe
              directory containing additional configuration files for
              the pipe metrics


       Environment variables with the prefix PCP_ are used to
       parameterize the file and directory names used by PCP.  On each
       installation, the file /etc/pcp.conf contains the local values
       for these variables.  The $PCP_CONF variable may be used to
       specify an alternative configuration file, as described in

SEE ALSO         top

       PCPIntro(1), pmval(1), pmcd(1), getpwent(3), getgrent(3),
       pmStore(3), pcp.conf(5) and pcp.env(5).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨⟩ on 2023-12-22.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-12-16.)  If you discover any rendering
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Performance Co-Pilot               PCP                       PMDAPIPE(1)