Each domain has one or more roles. Each role defines a service or a subset of related services. The roles are scripts which automate the process of deploying a new domain and also configure them based on the parameters available in the main sNow! configuration file (snow.conf).
The active-domains.conf file provides a list of sNow! domains and the associated roles which define the services provided by each domain. You can modify this list at your convenience. For instance, you may want to only a deploy system for installing bare metal nodes or you may want a full system with batch queue manager, monitoring, centralised syslog, ldap user authentication etc.
The first column of the active-domains.conf file contains the hostname of the domain, the second column contains the role or list or roles associated with the domain. Each domain can have one or more roles. In the case of multiple roles, use a comma separated list with no spaces.
If a domain has multiple roles, each role script will be executed in the order defined in domains.conf. This file will be automatically generated with the “snow init” command, as described in Section 6.4. The current available roles are located in /sNow/snow-tools/etc/roles.d. This document provides information of all the available roles.
The roles are responsible for populating most of the files located in $SNOW_CONF but there is no mechanism to synchronise those files. Whatever is modified in the $SNOW_CONF, inside a domain or inside a compute node, is not going to be synchronised across the cluster. In order to do that, you should consider using a configuration manager like Ansible, CFEngine or Puppet. Given the complexity involved, configuration managers are outside the scope of sNow!
The file /sNow/snow-tools/etc/active-domains.conf-example contains the most popular roles used in general HPC clusters.
To enable those roles, copy the example file as your working file:
cp -p /sNow/snow-tools/etc/active-domains.conf-example /sNow/snow-tools/etc/active-domains.conf
The following lines represent a typical example of an active-domains.conf configuration file. Add or delete lines as required by your installation needs.
hostname roles
-----------------------------
snow01 snow
ldap01 ldap-master
slurm01 slurmctld-master
monitor01 monitor
syslog01 syslog
login01 login
slurmdb01 slurmdbd
proxy01 proxy
deploy01 deploy