firecracker-microvm/firecracker · error

Unable to open or read from the configuration file

Error message

Unable to open or read from the configuration file

What it means

Error "Unable to open or read from the configuration file" thrown in firecracker-microvm/firecracker.

Source

Thrown at src/firecracker/src/main.rs:390

        let metrics_config = MetricsConfig {
            metrics_path: PathBuf::from(metrics_path),
            emit_id: false,
            properties: None,
        };
        init_metrics(metrics_config).map_err(MainError::MetricsInitialization)?;
    }

    let mut seccomp_filters: BpfThreadMap = SeccompConfig::from_args(
        arguments.flag_present("no-seccomp"),
        arguments.single_value("seccomp-filter"),
    )
    .and_then(seccomp::get_filters)
    .map_err(MainError::SeccompFilter)?;

    let vmm_config_json = arguments
        .single_value("config-file")
        .map(fs::read_to_string)
        .map(|x| x.expect("Unable to open or read from the configuration file"));

    let metadata_json = arguments
        .single_value(MMDS_CONTENT_ARG)
        .map(fs::read_to_string)
        .map(|x| x.expect("Unable to open or read from the mmds content file"));

    let boot_timer_enabled = arguments.flag_present("boot-timer");
    let pci_enabled = arguments.flag_present("enable-pci");
    let api_enabled = !arguments.flag_present("no-api");
    let api_payload_limit = arg_parser
        .arguments()
        .single_value("http-api-max-payload-size")
        .map(|lim| {
            lim.parse::<usize>()
                .expect("'http-api-max-payload-size' parameter expected to be of 'usize' type.")
        })
        // Safe to unwrap as we provide a default value.
        .unwrap();

View on GitHub (pinned to 0a745def42)

Solutions

1. Verify the configuration file path exists, is readable by the firecracker process, and contains valid JSON.
2. Check file permissions and the jailer chroot path mapping if running jailed.

When it happens

Trigger: Thrown at src/firecracker/src/main.rs:390 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/44fd846b9f8ee79a. Report an issue: GitHub.