AI agents call journalctl to retrieve information from Yaver without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
boot | boolean | — | |
unit | string | — | Service unit (e.g. nginx, docker, sshd) |
lines | integer | — | |
since | string | — | e.g. '1 hour ago', '2024-01-01' |
priority | string | — | emerg, alert, crit, err, warning, notice, info, debug |
Parameters from the server's own tool schema.
Even though journalctl only reads data, uncontrolled read access leaks sensitive information and racks up API costs — an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.
Attacks that exploit this kind of access
Query systemd journal logs with unit, priority, boot, and time filters. It is categorised as a Read tool in the Yaver MCP Server, which means it retrieves data without modifying state.
journalctl accepts 5 parameters: boot, unit, lines, since, priority. The full parameter table on this page comes from the server's own tool schema.
Register the Yaver MCP server in PolicyLayer and add a rule for journalctl: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Yaver. Nothing to install.
journalctl is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the journalctl rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for journalctl. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
journalctl is provided by the Yaver MCP server (yaver-cli). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.