$PCP_BINADM_DIR/pmsnap [-NV?] [-c configs] [-C dir] [-f format] [-n names] [-o dir]
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 archives 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;
- 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.
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.
- Add an appropriate entry for pmsnap in the root user's crontab. An example is supplied in $PCP_VAR_DIR/config/pmlogger/crontab.
- 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 given.
pmsnap should not be invoked immediately after pmlogger_daily has rolled the logs because the new archives 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:
- -c config-pattern
Only process lines in the control file which match the config-pattern regular expression in the Config column.
- -C dir
The control file is located in the directory dir rather than in the default $PCP_PMSNAPCONTROL_PATH location.
- -f format
Set output image format. The defaults format is png.
- -n name-pattern
Only process lines in the control file which match the name-pattern regular expression (see egrep(1)) in the Name column.
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 for debugging.
- -o dir
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.
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.
pmsnap control file
summary view for pmchart
sample HTML page for summary snapshot
PCP archive folio for the host hostname, as generated by pmlogger_check
example crontab entry
cron(1), crontab(1), egrep(1), pmafm(1), pmchart(1), pmlc(1), pmlogger(1) and pmlogger_daily(1).