Genders and PDSH

Note

Genders & PDSH functionality is not available or useful on a single node research environment, this page only applies to multi-node research environments

A combination of genders and pdsh can allow for management and monitoring of multiple nodes at a time. OpenFlight provides a build of PDSH that integrates with the rest of the User Suite.

Installing nodeattr and pdsh

Nodeattr and pdsh can be installed using the yum package manager, simply:

sudo yum -y install flight-pdsh

Once installed, the pdsh command will be available to active OpenFlight User Suite sessions (use flight start to activate the session). The priority of the OpenFlight pdsh command in the path can be configured with:

flight config set pdsh.priority X

Where X is one of:

  • system - Prefer system PDSH

  • embedded - Prefer OpenFlight PDSH

  • disabled - Do not include OpenFlight PDSH in PATH

Note

OpenFlight PDSH defaults system priority, to ensure that the OpenFlight User Environment uses the OpenFlight PDSH, set the priority to embedded after installation (flight config set pdsh.priority embedded)

Finding the names of your compute nodes

An OpenFlight Compute research environment may contain any number of compute nodes depending on your research environment size. The hostnames of compute nodes usually follow a sequential order (e.g. node01, node02, node03… node10). OpenFlight Compute automatically creates a list of compute node names and uses them to populate a genders group called nodes. This genders file can be found at /opt/flight/etc/genders.

Users can find the names of their compute nodes by using the nodeattr command; e.g.

  • nodeattr -s nodes
    • shows a space-separated list of current compute node hostnames

  • nodeattr -c nodes
    • shows a comma-separated list of current compute node hostnames

  • nodeattr -n nodes
    • shows a new-line-separated list of current compute node hostnames

The login node hostname for Flight Compute research environments launched using default templates is always gateway1.

Using PDSH

Users can run a command across all compute nodes at once using the pdsh command. This can be useful if users want to make a change to all nodes in the research environment - for example, installing a new software package. The pdsh command can take a number of parameters that control how commands are processed; for example:

  • pdsh -g all uptime
    • executes the uptime command on all available compute and login nodes in the research environment

  • pdsh -g nodes 'sudo yum -y install screen'
    • use yum to install the screen package as the root user on all compute nodes

  • pdsh -g nodes -f 1 df -h /tmp
    • executes the command df -h /tmp on all compute nodes of the research environment, one at a time (fanout=1)

  • pdsh -w node01,node03 which ldconfig
    • runs the which ldconfig command on two named nodes only