pssh

pssh is a utility for parallel execution of commands over ssh.

It parallelises the initial connection, and the command(s) specified in each -command argument. If any of the commands exit with non-zero code, no further commands are run.

Consider the difference between:

• -command xx -command yy

  This will parallelise xx, check that exit codes from all nodes were zero, then parallelise yy, then check that exit codes from all nodes were zero.

• -command 'xx ; yy'

  This will parallelise xx ; yy, thus ignoring the exit code of xx and only acting on the exit codes of yy.

• -command 'xx && yy'

  Standard shell rules apply. e.g. (if using bash) yy will only be run if xx exited with code zero.

Run

pssh \
    -user remote_username \
    -key ~/.ssh/id_rsa \
    -hosts 'node0[1-3].somecluster.example.com:22' \
    -command hostname \
    -command 'echo "More commands"'

Arguments

• -command (string(s)) See below.
• -colour (boolean) Produce colour output
• -hosts(string) List of hosts for ssh connections
  • Use "a;b;c" to specify three hosts, a, b and c
  • Use "node[0-2,5].example.com" to specify node0.example.com, node1.example.com, node2.example.com and node5.example.com
  • Use "{london,paris,berlin}.example.com" to specify london.example.com, paris.example.com and berlin.example.com
  • The above can be combined to a limited extent, e.g. use "aaa;pre{bbb[1-3],ccc[5,8]}post;zzz" to specify:
    • aaa
    • prebbb1post, prebbb2post, prebbb3post
    • preccc5post, preccc8post
    • zzz
• -key (string) Name of private key file, e.g. $HOME/.ssh/id_rsa
• -timeout (int) Timeout (in seconds) of the initial ssh connections
• -user (string) User name for ssh connections
• -verbose (boolean) Produce verbose output

Commands

• Check for file contents, and abort if contents do not exist on all hosts:

  pssh -user username -key /path/to/id_rsa \
      -hosts 'node0[0-9].cluster.example.com:22' \
      -command 'grep localhost /etc/hosts' \
      -command 'echo "Found localhost in /etc/hosts"'

• Check for file contents, and continue even if contents do not exist on all hosts:

  pssh -user username -key /path/to/id_rsa \
      -hosts 'node0[0-9].cluster.example.com:22' \
      -command 'grep localhost /etc/hosts ; /bin/true' \
      -command 'echo "localhost may or may not be in /etc/hosts"'

• Complex scriptlet

  pssh -user username -key /path/to/id_rsa \
      -hosts 'node0[0-9].cluster.example.com:22' \
      -command 'echo "Your scriptlet here" | grep script ; echo "Multiple commands are ok."'