firecracker-microvm/firecracker · error

'start-time-cpu-us' parameter expected to be of 'u64' type.

Error message

'start-time-cpu-us' parameter expected to be of 'u64' type.

What it means

Error "'start-time-cpu-us' parameter expected to be of 'u64' type." thrown in firecracker-microvm/firecracker.

Source

Thrown at src/firecracker/src/main.rs:434

            lim.parse::<usize>()
                .expect("'mmds-size-limit' parameter expected to be of 'usize' type.")
        })
        .unwrap_or_else(|| api_payload_limit);

    if api_enabled {
        let bind_path = arguments
            .single_value("api-sock")
            .map(PathBuf::from)
            .expect("Missing argument: api-sock");

        let start_time_us = arguments.single_value("start-time-us").map(|s| {
            s.parse::<u64>()
                .expect("'start-time-us' parameter expected to be of 'u64' type.")
        });

        let start_time_cpu_us = arguments.single_value("start-time-cpu-us").map(|s| {
            s.parse::<u64>()
                .expect("'start-time-cpu-us' parameter expected to be of 'u64' type.")
        });

        let parent_cpu_time_us = arguments.single_value("parent-cpu-time-us").map(|s| {
            s.parse::<u64>()
                .expect("'parent-cpu-time-us' parameter expected to be of 'u64' type.")
        });

        let process_time_reporter =
            ProcessTimeReporter::new(start_time_us, start_time_cpu_us, parent_cpu_time_us);

        api_server_adapter::run_with_api(
            &mut seccomp_filters,
            vmm_config_json,
            bind_path,
            instance_info,
            process_time_reporter,
            boot_timer_enabled,
            pci_enabled,

View on GitHub (pinned to 0a745def42)

Solutions

1. Pass a non-negative 64-bit integer for the start-time-cpu-us metadata value.
2. Check the config file JSON types; the value must be a number, not a string.

When it happens

Trigger: Thrown at src/firecracker/src/main.rs:434 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of firecracker-microvm/firecracker@0a745def42 (2026-08-19). Data as JSON: /api/errors/86d154f9b8355306. Report an issue: GitHub.