The default installation directory for the IBM Instana host agent on Linux systems is /opt/instana/agent. This location adheres to the Linux Filesystem Hierarchy Standard (FHS), which designates the /opt directory for optional, add-on software packages. The one-liner installation script, which is the recommended method, automatically unpacks and configures the agent within this path. All agent binaries, configuration files (in the etc subdirectory), and data/log files are contained within this main directory structure, providing a standardized and isolated environment for the agent's operation.

A. /var/lib/instana is a path for variable state information or data files, not the primary installation directory for the agent's binaries and libraries.

B. /opt/instana/agent/etc/ is a subdirectory within the main installation folder that specifically houses the agent's configuration files, such as configuration.yaml.

D. /etc/default/instana is a file path used to store default environment variables for the Instana agent service, not the installation directory itself.

1. IBM Documentation, "Installing the host agent on Linux": In the "One-liner" section, the documentation explicitly states, "The agent is installed into /opt/instana/agent." This is presented as the standard outcome of the preferred installation method.

2. IBM Documentation, "Host agent files": This document details the agent's file system layout, confirming the root location. It states, "The Instana host agent files are in /opt/instana/agent." It then lists the subdirectories, including bin, data, and etc, reinforcing that /opt/instana/agent is the parent installation directory.