pssh is a program for executing ssh in parallel on a number of hosts. It provides features such as sending input to all of the processes, passing a password to ssh, saving output to files, and timing out.
The PSSH_NODENUM and PSSH_HOST environment variables are sent to the remote host. The PSSH_NODENUM variable is assigned a unique number for each ssh connection, starting with 0 and counting up. The PSSH_HOST variable is assigned the name of the host as specified in the hosts list.