Understanding Application SSH
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This document describes details about the Elastic Runtime SSH components for access to deployed application instances. Elastic Runtime supports native SSH access to applications and load balancing of SSH sessions with the load balancer for your Elastic Runtime deployment.
The SSH Overview document describes procedural and configuration information about application SSH access.
The Elastic Runtime SSH includes the following central components, which are described in more detail below:
If these components are deployed and configured correctly, they provide a simple and scalable way to access containers apps and other long running processes (LRPs).
The SSH daemon is a lightweight implementation that is built around the Go SSH library. It supports command execution, interactive shells, local port forwarding, and secure copy. The daemon is self-contained and has no dependencies on the container root file system.
The daemon is focused on delivering basic access to application instances in Elastic Runtime. It is intended to run as an unprivileged process, and interactive shells and commands will run as the daemon user. The daemon only supports one authorized key, and it is not intended to support multiple users.
The daemon can be made available on a file server and Diego LRPs that want to use it can include a download action to acquire the binary and a run action to start it. Elastic Runtime applications will download the daemon as part of the lifecycle bundle.
The SSH proxy hosts the user-accessible SSH endpoint and is responsible for authentication, policy enforcement, and access controls in the context of Elastic Runtime. After a user has successfully authenticated with the proxy, the proxy will attempt to locate the target container and create an SSH session to a daemon running inside the container. After both sessions have been established, the proxy will manage the communication between the user’s SSH client and the container’s SSH Daemon.