Google Cloud VM Manager vs Rex

Google Cloud VM Manager manages operating systems across Windows and Linux VM fleets running on Compute Engine. Its tools cover patch management, OS inventory and OS policies. Patch jobs apply updates on demand or on a schedule, report compliance, and can use selected approvals and pre- or post-patching scripts. OS inventory collects hostnames, OS and kernel versions, installed packages, available updates, Windows applications and OS vulnerabilities. OS policies centralize software configuration deployment, maintenance and reporting. Teams can use the Google Cloud console, Google Cloud CLI or OS Config API; Terraform can extend scope across projects. The service supports projects inside VPC Service Controls perimeters, but patch jobs operate on VMs in one project at a time. A free tier covers 100 VMs per Cloud Billing account per month, and limited-functionality mode is available at no cost for unlimited VMs. After the free tier, the listed charge is $0.003 per hour per VM with an active OS Config agent.

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.