Parallel Shell

The cluster comes with a simple parallel shell named pdsh. The pdsh shell is handy for running commands across the cluster. See the man page, which describes the capabilities of pdsh in detail. One of the useful features is the capability of specifying all or a subset of the cluster. For example:

pdsh -a <command> targets the <command> to all nodes of the cluster, including the master.

pdsh -a -x node00 <command> targets the <command> to all nodes of the cluster except the master.

pdsh -w node[01-08] <command> targets the <command> to the 8 nodes of the cluster named node01, node02, $\ldots$, node08.

Another utility that is useful for formatting the output of pdsh is dshbak. Here we will show some handy uses of pdsh.

• Show the current date and time on all nodes of the cluster.
  pdsh -a date

• Show the current load and system uptime for all nodes of the cluster.
  pdsh -a uptime

• Show all processes with the substring mpd in their name on the cluster.
  pdsh -a ps augx | grep mpd

• Cleanup MPI files and sockets fom all nodes in the system. This can be handy in removing leftover files from a earlier program or system crash.

  pdsh -a mpdcleanup

• Remove all instances of pvm temporary files from the cluster. This can be handy in removing leftover files from a earlier program or system crash.
  pdsh -a /bin/rm -f /tmp/pvm*

• The utility dshbak formats the output from pdsh by consolidating the output from each node. The option -c shows identical output from different nodes just once.

  pdsh -a ls -l /etc/ntp | dshbak -c

  Here is a sample output:

  [amit@onyx amit]$ pdsh -a ls -l /etc/ntp | dshbak -c
  ----------------
  ws[01-16]
  ----------------
   total 16
   -rw-r--r--  1 root root   8 Jun  4 11:53 drift
   -rw-------  1 root root 266 Jun  4 11:53 keys
   -rw-r--r--  1 root root  13 Jun  4 11:53 ntpservers
   -rw-r--r--  1 root root  13 Jun  4 11:53 step-tickers
  ----------------
  ws00
  ----------------
   total 16
   -rw-r--r--    1 ntp      ntp             8 Sep  5 21:51 drift
   -rw-------    1 ntp      ntp           266 Feb 13  2003 keys
   -rw-r--r--    1 root     root           58 Oct  3  2003 ntpservers
   -rw-r--r--    1 ntp      ntp            23 Oct  3  2003 step-tickers
  ----------------
  ws[17-32]
  ----------------
   total 16
   -rw-r--r--  1 root root   8 May 27 13:31 drift
   -rw-------  1 root root 266 May 27 13:31 keys
   -rw-r--r--  1 root root  13 May 27 13:31 ntpservers
   -rw-r--r--  1 root root  13 May 27 13:31 step-tickers
  [amit@onyx amit]$