1PMDAJBD2(1)                 General Commands Manual                PMDAJBD2(1)
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NAME

6       pmdajbd2  - journal block device (JBD) performance metrics domain agent
7       (PMDA)
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SYNOPSIS

10       $PCP_PMDAS_DIR/jbd2/pmdajbd2 [-d domain] [-l  logfile]  [-j  path]  [-U
11       username]
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DESCRIPTION

14       pmdajbd2  is  a  Performance Metrics Domain Agent (PMDA) which extracts
15       performance metrics from the Journal Block Device subsystem (version 2)
16       in  the  Linux  kernel.   These  metrics  are exported by the kernel in
17       procfs files, one file per block device.  The JBD2 subsystem is used by
18       several filesystems including ext3, ext4 and ocfs2.
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20       The jbd2 PMDA exports metrics that measure detailed journal transaction
21       information, such as time spent  waiting  and  locked,  request  rates,
22       blocks used and so on.
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24       A brief description of the pmdajbd2 command line options follows (these
25       are only relevant when running the PMDA as  a  daemon,  and  not  as  a
26       shared library):
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28       -d   It  is absolutely crucial that the performance metrics domain num‐
29            ber specified here is unique  and  consistent.   That  is,  domain
30            should  be  different for every PMDA on the one host, and the same
31            domain number should be used for the same PMDA on all hosts.
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33       -l   Location of the log file.  By default, when running as a daemon  a
34            log  file  named  jbd2.log  is written in the current directory of
35            when pmdajbd2 is started, i.e.   $PCP_LOG_DIR/pmcd.   If  the  log
36            file  cannot  be  created or is not writable, output is written to
37            the standard error instead.  When running in shared library  mode,
38            and diagnostic information will be written into the pmcd log file,
39            namely $PCP_LOG_DIR/pmcd/pmcd.log.
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41       -j   Allows an alternate path to the jbd2 statistics files to be speci‐
42            fied.  The default path is /proc/fs/jbd2.
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44       -U   User account under which to run the agent.  The default is the un‐
45            privileged "pcp" account in current versions of PCP, but in  older
46            versions the superuser account ("root") was used by default.
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INSTALLATION

49       This  PMDA  is  installed  by  default  and  in the shared library mode
50       (rather than as a separate daemon to pmcd(1)).  Thus, the  names,  help
51       text  and  values  for  the  jbd2  performance metrics should always be
52       available.
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54       If you do not use these metrics you can remove this PMDA, do  the  fol‐
55       lowing as root:
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57            # cd $PCP_PMDAS_DIR/jbd2
58            # ./Remove
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60       If you want to enable the installation again, do the following as root:
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62            # cd $PCP_PMDAS_DIR/jbd2
63            # ./Install
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65       pmdajbd2  is launched by pmcd(1) and should never be executed directly.
66       The Install and Remove scripts notify pmcd(1) when  the  agent  is  in‐
67       stalled or removed.
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FILES

70       $PCP_PMCDCONF_PATH
71                 command line options used to launch pmdajbd2
72       $PCP_PMDAS_DIR/jbd2/help
73                 default help text file for the jbd2 metrics
74       $PCP_PMDAS_DIR/jbd2/Install
75                 installation script for the pmdajbd2 agent
76       $PCP_PMDAS_DIR/jbd2/Remove
77                 undo installation script for the pmdajbd2 agent
78       $PCP_LOG_DIR/pmcd/jbd2.log
79                 default  log  file  for  error messages and other information
80                 from pmdajbd2
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PCP ENVIRONMENT

83       Environment variables with the prefix PCP_ are used to parameterize the
84       file  and  directory names used by PCP.  On each installation, the file
85       /etc/pcp.conf contains the  local  values  for  these  variables.   The
86       $PCP_CONF  variable may be used to specify an alternative configuration
87       file, as described in pcp.conf(5).
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SEE ALSO

90       PCPIntro(1), pmcd(1), pcp.conf(5) and pcp.env(5).
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