Parallel SSH program.
pssh -i -H "{{host1}} {{host2}}" {{hostname -i}}
pssh -H {{host1}} -H {{host2}} -o {{path/to/output_dir}} {{hostname -i}}
pssh -i -h {{path/to/hosts_file}} {{hostname -i}}
pssh -i -h {{path/to/hosts_file}} -A -l {{root_username}} {{hostname -i}}
pssh -i -h {{path/to/hosts_file}} -x "{{-O VisualHostKey=yes}}" {{hostname -i}}
pssh -i -h {{path/to/hosts_file}} -p {{10}} '{{cd dir; ./script.sh; exit}}'