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NAME | SYNOPSIS | DESCRIPTION | INSTALLATION | FILES | PCP ENVIRONMENT | DEBUGGING OPTIONS | SYNOPSIS | SEE ALSO | COLOPHON |
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KERNEL_PMDAS(1) General Commands Manual KERNEL_PMDAS(1)
pmdaaix, pmdadarwin, pmdafreebsd, pmdalinux, pmdanetbsd,
pmdaopenbsd, pmdasolaris, pmdawindows - operating system kernel
performance metrics domain agents
$PCP_PMDAS_DIR/aix/pmdaaix [-D debug] [-d domain] [-l logfile] [-U
username]
$PCP_PMDAS_DIR/darwin/pmdadarwin [-D debug] [-d domain] [-l
logfile] [-U username]
$PCP_PMDAS_DIR/freebsd/pmdafreebsd [-D debug] [-d domain] [-l
logfile] [-U username]
$PCP_PMDAS_DIR/linux/pmdalinux [-A] [-D debug] [-d domain] [-l
logfile] [-U username]
$PCP_PMDAS_DIR/netbsd/pmdanetbsd [-D debug] [-d domain] [-l
logfile] [-U username]
$PCP_PMDAS_DIR/netbsd/pmdaopenbsd [-D debug] [-d domain] [-l
logfile] [-U username]
$PCP_PMDAS_DIR/solaris/pmdasolaris [-D debug] [-d domain] [-l
logfile] [-U username]
$PCP_PMDAS_DIR/windows/pmdawindows [-D debug] [-d domain] [-l
logfile] [-U username]
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 instead.
-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).
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.
$PCP_PMDAS_DIR/[platform]/help
default help text file for the the kernel metrics
$PCP_LOG_DIR/pmcd/[platform].log
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 pcp.conf(5).
The -D or --debug option enables the output of additional
diagnostics on stderr to help triage problems, although the
information is sometimes cryptic and primarily intended to provide
guidance for developers rather end-users. debug is a comma
separated list of debugging options; use pmdbg(1) with the -l
option to obtain a list of the available debugging options and
their meaning.
Debugging options specific to pmdaaix, pmdafreebsd, pmdanetbsd,
pmdaopenbsd and pmdasolaris are as follows:
┌────────┬─────────────────────┐
│ Option │ Description │
├────────┼─────────────────────┤
│ appl0 │ verbose diagnostics │
└────────┴─────────────────────┘
Debugging options specific to pmdalinux are as follows:
┌────────┬──────────────────────┐
│ Option │ Description │
├────────┼──────────────────────┤
│ appl1 │ disk-related metrics │
├────────┼──────────────────────┤
│ appl8 │ filesys metrics │
└────────┴──────────────────────┘
PCPIntro(1), dbpmda(1), pmcd(1), pcp.conf(5) and pcp.env(5).
This page is part of the PCP (Performance Co-Pilot) project.
Information about the project can be found at
⟨http://www.pcp.io/⟩. If you have a bug report for this manual
page, send it to pcp@groups.io. This page was obtained from the
project's upstream Git repository
⟨https://github.com/performancecopilot/pcp.git⟩ on 2025-08-11.
(At that time, the date of the most recent commit that was found
in the repository was 2025-08-11.) 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
man-pages@man7.org
Performance Co-Pilot PCP KERNEL_PMDAS(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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