# 6. Host specification

PRRTE identifies hosts on which to launch processes by:

1. A Resource Manager (RM) telling PRRTE which hosts to use

2. The user providing a hostfile (also sometimes called a “machine file”)

3. The user providing a list of hosts on the command line

The sections below describe each of these in more detail.

- 6.1. Resource Manager-Provided Hosts
- 6.2. Hostfiles
- 6.3. Listing Hosts on the Command Line
- 6.4. Relative host indexing