Which automation tool does not require an agent to be installed on managed nodes?

Ansible is an agentless automation tool, which means it does not require any software agents to be installed on the managed nodes. Instead, Ansible leverages SSH (Secure Shell) for communication with Unix-based systems and WinRM (Windows Remote Management) for Windows systems. This agentless approach simplifies configuration management in environments where it may be impractical or undesirable to install additional software.

The decision to have no agents enables quicker deployment and reduces the overhead associated with maintaining and updating agents on multiple servers. Additionally, it enhances security since there are fewer potential attack points due to not having an installed agent running on the systems managed.

The other tools mentioned, such as Puppet, Chef, and SaltStack, typically require an agent to be installed on the managed nodes. These agents run continuously, making configuration changes and reporting back to the management server. While these tools offer robust configuration management capabilities, the requirement for agents can complicate deployment and increase management overhead compared to Ansible's more straightforward approach.