## Name

Boot Parameters - optional parameters accepted by the kernel

## Description

Serenity's kernel can process parameters at boot time.
This functionality is used to control or augment the state of features during the initial
startup of the system.

### Options

The kernel boot parameters take the form of **`{option_name}={value}`**, where the **`={value}`**
trailer can be omitted for specific parameters.

List of options:

-   **`acpi`** - This parameter expects one of the following values. **`on`** - Boot with full ACPI support, using ACPI
    Machine Language interpretation (default). **`limited`** - Boot with limited ACPI support. **`off`** - Don't initialize ACPI at all.

-   **`ahci_reset_mode`** - This parameter expects one of the following values. **`controllers`** - Reset just the AHCI controller on boot (default).
    **`aggressive`** - Reset the AHCI controller, and all AHCI ports on boot.

-   **`boot_prof`** - If present on the command line, global system profiling will be enabled
    as soon as possible during the boot sequence. Allowing you to profile startup of all applications.

-   **`disable_physical_storage`** - If present on the command line, neither AHCI, or IDE controllers will be initialized on boot.

-   **`disable_ps2_mouse`** - If present on the command line, no PS2 mouse will be attached.
-   **`disable_uhci_controller`** - If present on the command line, the UHCI controller will not be initialized on boot.

-   **`disable_virtio`** - If present on the command line, virtio devices will not be detected, and initialized on boot.

-   **`early_boot_console`** - This parameter expects **`on`** or **`off`** and is by default set to **`on`**.
    When set to **`off`**, the kernel will not initialize any early console to show kernel dmesg output.
    When set to **`on`**, the kernel will try to initialize either a text mode console (if VGA text mode was detected)
    or framebuffer console, based on what the Multiboot bootloader specified on the physical address, width, height
    and bit color depth.

-   **`enable_ioapic`** - This parameter expects **`on`** or **`off`** and is by default set to **`on`**.
    When set to **`off`**, the kernel will initialize the two i8259 PICs.
    When set to **`on`**, the kernel will try to initialize the IOAPIC (or IOAPICs if there's more than one),
    but only if **`acpi`** is set to **`limited`** or **`on`**, and a `MADT` (APIC) table is available.
    Otherwise, the kernel will fallback to use the i8259 PICs.

-   **`graphics_subsystem_mode`** - This parameter expects one of the following values. **`on`**- Boot into the graphical environment if possible (default). **`off`** - Boot into text mode, don't initialize any driver. **`limited`** - Boot into the pre-defined framebuffer that the bootloader
    has set up before booting the Kernel, don't initialize any driver.

-   **`hpet`** - This parameter expects one of the following values. **`periodic`** - The High Precision Event Timer should
    be configured in a periodic mode. **`nonperiodic`** - The High Precision Event Timer should eb configure din non-periodic mode.

-   **`init`** - This parameter expects the fully qualified path to the init program the Kernel should launch after boot.
    This defaults to [`SystemServer`(7)](help://man/7/SystemServer).

-   **`init_args`** - This parameter expects a set of arguments to pass to the **`init`** program.
    The value should be a set of strings separated by `,` characters.

-   **`i8042_presence_mode`** - This parameter expects one of the following values:
    **`aggressive-test`** - The i8042 initialization sequence should only try an aggressive presence test.
    **`auto`** - The i8042 initialization sequence should try to check if ACPI says i8042 exists, and if not an aggressive presence test should take place to determine presence.
    **`none`** - Assume there's no i8042 controller in the system.
    **`force`** - Assume there's i8042 controller in the system.

-   **`i8042_first_port_translation`** - This parameter expects **`on`** or **`off`** and is by default set to **`off`**.
    When set to **`off`**, the kernel will not enable first PS2 port translation.
    When set to **`on`**, the kernel will enable first PS2 port translation.

-   **`panic`** - This parameter expects **`halt`** or **`shutdown`**. This is particularly useful in CI contexts.

-   **`pci`** - This parameter expects **`ecam`**, **`io`** or **`none`**. When selecting **`none`**
    the kernel will not use PCI resources/devices.

-   **`root`** - This parameter configures the device to use as the root file system. It defaults to **`/dev/hda`** if unspecified.

-   **`pcspeaker`** - This parameter controls whether the kernel can use the PC speaker or not. It defaults to **`off`** and can be set to **`on`** to enable the PC speaker.

-   **`smp`** - This parameter expects a binary value of **`on`** or **`off`**. If enabled kernel will
    enable available APs (application processors) and use them with the BSP (Bootstrap processor) to
    schedule and run threads.
    This parameter defaults to **`off`**. This parameter requires **`enable_ioapic`** to be enabled
    and a `MADT` (APIC) table to be available.

-   **`nvme_poll`** - This parameter configures the NVMe drive to use polling instead of interrupt driven completion.

-   **`xhci_poll`** - This parameter configures the xHCI driver to use polling instead of interrupt driven completion.

-   **`system_mode`** - This parameter is not interpreted by the Kernel, and is made available at `/sys/kernel/system_mode`. SystemServer uses it to select the set of services that should be started. Common values are:

    -   **`graphical`** (default) - Boots the system in the normal graphical mode.
    -   **`self-test`** - Boots the system in self-test, validation mode.
    -   **`text`** - Boots the system in text only mode. (You may need to also set **`graphics_subsystem_mode=off`**.)

-   **`time`** - This parameter expects one of the following values. **`modern`** - This configures the system to attempt
    to use High Precision Event Timer (HPET) on boot. **`legacy`** - Configures the system to use the legacy programmable interrupt
    time for managing system team.
-   **`vmmouse`** - This parameter expects a binary value of **`on`** or **`off`**. If enabled and
    running on a VMWare Hypervisor, the kernel will enable absolute mouse mode.

-   **`disable_kaslr`** - If present on the command line, the KASLR security mitigation will be disabled.

## See also

-   [`SystemServer`(7)](help://man/7/SystemServer).
