pmdakernel(1) — Linux manual page


KERNEL_PMDAS(1)          General Commands Manual         KERNEL_PMDAS(1)

NAME         top

       pmdaaix, pmdadarwin, pmdafreebsd, pmdalinux, pmdanetbsd,
       pmdasolaris, pmdawindows - operating system kernel performance
       metrics domain agents

SYNOPSIS         top

       $PCP_PMDAS_DIR/aix/pmdaaix [-d domain] [-l logfile] [-U username]
       $PCP_PMDAS_DIR/darwin/pmdadarwin [-d domain] [-l logfile] [-U
       $PCP_PMDAS_DIR/freebsd/pmdafreebsd [-d domain] [-l logfile] [-U
       $PCP_PMDAS_DIR/linux/pmdalinux [-A] [-d domain] [-l logfile] [-U
       $PCP_PMDAS_DIR/netbsd/pmdanetbsd [-d domain] [-l logfile] [-U
       $PCP_PMDAS_DIR/solaris/pmdasolaris [-d domain] [-l logfile] [-U
       $PCP_PMDAS_DIR/windows/pmdawindows [-d domain] [-l logfile] [-U

DESCRIPTION         top

       Each supported platform has a kernel Performance Metrics Domain
       Agent (PMDA) which extracts performance metrics from the kernel
       of that platfrom.  A variety of platform-specific metrics are
       available, with an equally varied set of access mechanisms -
       typically this involves special system calls, or reading from
       files in kernel virtual filesystems such as the Linux sysfs and
       procfs filesystems.

       The platform kernel PMDA is one of the most critical components
       of the PCP installation, and must be as efficient and reliable as
       possible.  In all installations the default kernel PMDA will be
       installed as a shared library and thus executes directly within
       the pmcd(1) process.  This slightly reduces overheads associated
       with querying the metadata and values associated with these
       metrics (no message passing is required).

       Unlike many other PMDAs, the kernel PMDA exports a number of
       metric namespace subtrees, such as kernel, network, swap, mem,
       ipc, filesys, nfs, disk and hinv (hardware inventory).

       Despite usually running as shared libraries, most installations
       also include a stand-alone executable for the kernel PMDA.  This
       is to aid profiling and debugging activities, with dbpmda(1) for
       example.  In this case (but not for shared libraries), the
       following command line options are available:

       -A   Disables use of the credentials provided by PMAPI client
            tools, and simply runs everything under the "root" account.
            Only enable this option if you understand the risks
            involved, and are sure that all remote accesses will be from
            benevolent users.  If enabled, unauthenticated remote PMAPI
            clients will be able to access potentially sensitive
            performance metric values which an unauthenticated PMAPI
            client usually would not be able to.  Refer to CVE-2012-3419
            for additional details.

       -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
            [platform].log is written in the current directory of
            pmcd(1) when pmda[platform] 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

       -U   User account under which to run the agent.  The default is
            either the privileged "root" account on some platforms
            (Linux, for example) or the unprivileged "pcp" account
            (wherever possible).

INSTALLATION         top

       Access to the names, help text and values for the kernel
       performance metrics is available by default - unlike most other
       agents, no action is required to enable them and they should not
       be removed.

FILES         top

              default help text file for the the kernel metrics
              default log file for error messages and other information
              from the kernel PMDA.


       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), dbpmda(1), pmcd(1), 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
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Performance Co-Pilot               PCP                   KERNEL_PMDAS(1)