Pdsh: Difference between revisions

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Run <code>pdsh -L</code> to list all remote command modules available.  
Run <code>pdsh -L</code> to list all remote command modules available.  


For SSH support, you will need to install the <code>pdsh-rcmd-ssh</code> package.
==== SSH remote module ====
For SSH support, you will need to install the <code>pdsh-rcmd-ssh</code> package. Additional SSH arguments can be passed by passing in the PDSH_SSH_ARGS_APPEND environment variable. Eg:
{{Highlight
| code = # PDSH_SSH_ARGS_APPEND=”-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=error” pdsh -a uptime
| lang = terminal
}}


== Configuration ==
== Configuration ==

Revision as of 22:57, 23 January 2023

The pdsh command is a parallel version of the dsh (Distributed Shell). It is used to run commands on multiple remote hosts in parallel and supports a number of remote shell programs including SSH.

Cheat sheet

Action Command
Run a command on all hosts pdsh -a uptime
Run a command on all hosts EXCEPT one pdsh -a -x exclude-node uptime
Run a command on a set of hosts by hostname

Or by a specific gender (ie. attribute), see below.

pdsh -w node[0-10] uptimepdsh -w cpus=8 uptime
Collect the OS version on all hosts and group it pdsh -a cat /etc/redhat-release | dshbak -c

Installation

You can install pdsh from the epel repo. 

# yum -y install epel-release
# yum -y install pdsh pdsh-rcmd-ssh

Alternatively, install from source from the GitHub repo at: https://github.com/chaos/pdsh

Modules

Run pdsh -L to list all remote command modules available.

SSH remote module

For SSH support, you will need to install the pdsh-rcmd-ssh package. Additional SSH arguments can be passed by passing in the PDSH_SSH_ARGS_APPEND environment variable. Eg: 

# PDSH_SSH_ARGS_APPEND=”-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=error” pdsh -a uptime

Configuration

Genders file

The genders file can be used to give attributes to nodes in a cluster. It can be thought of as groups that can be used as a target when running pdsh commands. While the genders file isn't required, it's still a good idea to have set up because it allows the -a option to function properly.

The genders file is usually located at /etc/genders. Each line can contain one or more hosts and attributes are given as a comma delimited list. Here is an example genders file: 

ca-controller management
ca-login cluster-a,login
ca[001-168] cluster-a,cpus=4
cb-login cluster-b,login
cb[091-320] cluster-b,cpus=8

Using this example, you can target:

  • Only the control node with pdsh -w management
  • Only cluster A nodes with pdsh -w cluster-a
  • Only nodes with 8 CPUs with pdsh -w cpus=8

See also