etcsysctld

etcsysctld is a daemon designed to manage kernel parameter settings on Unix-like systems by centralizing configuration in /etc/sysctl.d and /etc/sysctl.conf. Its primary role is to load, validate, and apply values at boot and to refresh them at runtime in response to configuration changes, ensuring that the running kernel matches the defined policy.

Operation and behavior: The daemon reads files containing lines in the form key = value, where keys correspond to sysctl knobs. It determines an effective value based on file precedence and applies changes through the system’s sysctl interface, using /proc/sys or the kernel API. etcsysctld can monitor configuration directories for additions, removals, or edits and trigger a reload to keep the runtime state in sync with the configured state.

Configuration and usage: In typical deployments, etcsysctld is managed as a service by the system’s init system, such as systemd. It may offer command-line options to specify a configuration directory, enable verbose logging, or run in a dry-run mode for validation. Administrators can place files under the standard sysctl configuration paths to express policies that persist across reboots.

Relation to other tools: On many systems, systemd provides a built-in mechanism (systemd-sysctl) that reads /etc/sysctl.d and applies values at boot and runtime. etcsysctld represents an alternative or supplementary approach that some distributions may adopt, especially in environments requiring custom monitoring or policy enforcement beyond the standard tooling.

Security considerations: The daemon runs with elevated privileges to modify kernel parameters; careful validation of input, restricted write access to configuration directories, and thorough logging are essential to mitigate misconfigurations and abuse. See also: sysctl, /proc/sys, systemd-sysctl.