pmsnap is a shell script that is normally run periodically from
crontab(1) to generate graphic images of pmchart(1) performance
charts. These images can be in any of the supported pmchart
formats, including png, bmp, and jpeg, and may be incorporated
into the content offered by the local web server. By default
pmsnap generates no textual output unless some error or warning
condition is encountered.
pmsnap generates images according to its control file,
$PCP_PMSNAPCONTROL_PATH (or dir/control if the -C option is
specified), and uses archive logs created by pmlogger(1) or PCP
archive folios created by pmafm(1) and pmlogger_check(1). Before
attempting to configure pmsnap, it is strongly recommended that
pmlogger be configured according to the descriptions in
pmlogger_daily(1), pmlogger_check(1) and pmlogger(1).
Once pmlogger has been configured, it is necessary to configure
pmsnap as follows;
1. Edit the control file $PCP_PMSNAPCONTROL_PATH. The syntax
of this file is described in the comment at the head of
the file and an example is supplied for one and twelve
hour "Summary" performance charts for the local host.
Suitable arguments for pmchart are also described in the
comment. The user should consult pmchart for further
details. Note that when pmsnap is run, it globally
substitutes the string LOCALHOSTNAME with the name of the
local host in the control file.
2. Test the configuration by running
Without any arguments pmsnap will process every non-
comment line in $PCP_PMSNAPCONTROL_PATH. The output
images will be placed in the files named in the first
field of each line in the control file, with the file
format appended if necessary. If these file names do not
start with / or . then they are assumed relative to dir,
as specified with the -o option. The default dir is the
current directory. Note that if pmlogger has only been
recently started (within about the last 15 minutes),
snapshot images may not be produced and no error messages
will be issued - the reason is that pmchart can not use
very short archives and hence, neither can pmsnap. For
debugging purposes the -V flag should be used.
3. Add an appropriate entry for pmsnap in the root user's
crontab. An example is supplied in
4. Incorporate the pmsnap images into the local WWW content.
Usually, WWW pages use images that are relative to a
particular document root, so it is often convenient to use
the -o command line option to specify a sub-directory of
the local WWW content, and then create a web page in this
directory that shows the snapshot images with text and
other content appropriate to the local environment.
A sample HTML page, suitable for the Summary snapshot may be
found in $PCP_VAR_DIR/config/pmsnap/Summary.html.
Although pmsnap attempts to flush stdio(3) output buffers in the
relevant pmlogger processes before generating snapshots images,
this may fail for assorted reasons and no error message will be
pmsnap should not be invoked immediately after pmlogger_daily has
rolled the logs because the new archive logs will be too short to
obtain meaningful results. Note however that pmsnap will not
report errors from pmchart about not being able to comply with
the -A option on very short archives. In these cases no error
will be reported and no output images will be produced.
The available command line options are:
Only process lines in the control file which match the
config-pattern regular expression in the Config column.
The control file is located in the directory dir rather than
in the default $PCP_PMSNAPCONTROL_PATH location.
Set output image format. The defaults format is png.
Only process lines in the control file which match the name-pattern regular expression (see egrep(1)) in the Name
-N Enable a ``show me'' mode, where the actions are echoed, but
not executed, in the style of ``make -n''. Using -N in
conjunction with -V maximizes the diagnostic capabilities
The output images having file names which do not start with
/ or . will be placed in a directory relative to dir,
otherwise the output directory is relative to the current
directory (i.e. the default value for dir is ./). Note that
dir must be a writable directory path and may be on an NFS
or CIFS file system.
-V Enable verbose mode.
-? Display usage message and exit.
When either -n or -c are used, pmsnap will only process lines in
the control file which match all the supplied patterns. If no
patterns are given, then all lines will be processed. These
arguments allow multiple entries for pmsnap in crontab so that
different performance summary images can be generated at
different times or with different frequencies.
$PCP_PMSNAPCONTROL_PATHpmsnap control file
summary view for pmchart$PCP_VAR_DIR/config/pmsnap/Summary.html
sample HTML page for summary snapshot
PCP archive folio for the host hostname, as generated by
example crontab entry
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 email@example.com. This page was obtained from the
project's upstream Git repository
⟨https://github.com/performancecopilot/pcp.git⟩ on 2021-04-01.
(At that time, the date of the most recent commit that was found
in the repository was 2021-04-01.) 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 PMSNAP(1)