AWS Systems Manager State Manager vs Rex

AWS Systems Manager State Manager automates keeping managed nodes and other AWS resources in a state that customers define. Its associations specify the configuration to maintain, when to apply it and which resources to target. Targets can be selected by tags, AWS Resource Groups, individual node IDs or all managed nodes in the current Region and account. Associations can run immediately or later and accept most standard cron and rate expressions, but association cron expressions cannot specify months. On Linux, macOS and Windows Server managed nodes, State Manager can bootstrap software, schedule agent updates, configure network settings, join nodes to a Microsoft Active Directory domain and run scripts. Association run output can be stored in Amazon S3, and State Manager is supported as an event type and target type in Amazon EventBridge rules. It has no additional charge, although limits may apply. State Manager runs as a cloud service with an agent-based model. AWS Systems Manager follows a shared responsibility model: AWS protects cloud infrastructure, while customer responsibilities depend on the service, data and requirements. Third-party auditors assess Systems Manager under assurance programs including SOC, PCI, FedRAMP and HIPAA.

Rex is a free, open-source automation framework for managing local computers and remote machines over SSH. It runs self-hosted and agentless on Linux and Windows, with support also listed for RHEL/CentOS, Fedora, OpenWRT, BSDs, and Solaris. Projects keep inventory, environments, authentication details, and tasks in a Rexfile. You can combine local or remote execution, push or pull management, and imperative or declarative styles. Tasks can install packages, upload configuration files, start services, and trigger actions when files change. Rex uses a DSL compatible with Perl syntax and can be extended with Perl modules or custom code. Authentication documentation covers passwords, SSH keys, passphrases, external credential sources, and ssh-agent. The control host needs Perl and dependencies; managed hosts need Perl 5 and a valid SSH account. Installation is recommended through CPAN, with package-manager and source options. Apache 2.0 licensing applies to Rex and its parts.