rootless

Rootless is a term used to describe software, services, or environments that run without requiring root (superuser) privileges. In a rootless configuration, the majority of operations are performed by a non-privileged user; privileged actions are limited, and isolation mechanisms such as user namespaces, capabilities dropping, and sandboxing are employed to contain potential damage from misbehavior or compromise.

In containerization, rootless container runtimes run containers as non-privileged users. Examples include Podman in rootless mode and Docker in rootless mode. In these setups, the container's root user is mapped to an unprivileged host user, and operations that would normally require root are restricted. Benefits include safer experimentation and enhanced multi-tenant security; limitations include restricted access to certain host resources, need for kernel support for user namespaces, and sometimes reduced performance or compatibility with certain images or features.

Rootless operation can also apply to how software is installed and run, using per-user prefixes and avoiding the need for sudo. Package managers and runtimes that support user-space installations illustrate this, as do applications that can be started and managed entirely by a non-root user without affecting system-wide configuration.

Security considerations and limitations accompany rootless modes. They reduce the risk of privilege escalation and limit the potential impact of a compromised process, but they can complicate tasks that require privileged operations, such as binding to low-numbered ports, mounting file systems, or performing certain networking or hardware access. Some features may be blocked or unavailable in rootless configurations.