Adding Kernel Arguments at Boot Time

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On x86 platforms, you can set boot attributes and kernel arguments at boot time. These changes persist until the next time the system is booted.

Follow these general steps:

Boot the system.
```
$ reboot -p
```
The GRUB menu is displayed.
Edit your selected entry.
Exit the edit menu to proceed with the boot process.

To edit a specific menu entry, select the entry, then type e to edit it. On the GRUB edit screen, navigate to the $multiboot line, then type the additional boot option or kernel argument at the end of the line.

A $multiboot line with added arguments might resemble this example:

$multiboot /ROOT/transition/@/$kern $kern -B console=graphics -B $zfs_bootfs added-arguments

Note - When parameters are specified by using the eeprom utility and on the GRUB command line, the GRUB command line settings take precedence.

Supported Kernel Arguments

The following kernel arguments and options can be specified when you edit the GRUB menu at boot time:

unix

Specifies the kernel to boot.

–a

Prompts the user for configuration information.

–i altinit

Specifies an alternative executable as the primordial process. altinit is a valid path to an executable.

–k

Boots the system with the kernel debugger enabled

–m smf-options

Controls the boot behavior of the Service Management Facility (SMF)

There are two categories of options: recovery options and messages options.

–r

Specifies a reconfiguration boot.

The system probes all attached hardware devices and then assigns nodes in the file system to represent only those devices that are actually found.

–s

Boots the system to a single-user state.

–v

Boots the system with verbose messages enabled.

For example, to load the kernel debugger (kmdb) at boot time, you would edit the $multiboot line as follows. The change is shown in bold.

$multiboot /ROOT/transition/@/$kern $kern -B console=graphics -B $zfs_bootfs -k

For more information, see the kernel(8) man page.

Adding EEPROM Parameters

Aside from kernel arguments, you can pass EEPROM parameters to the kernel to be used at boot time. You must specify these with the –B option. Separate multiple property values with a comma.

acpi-user-options: Determines whether ACPI will be used or not. By default, ACPI is used.
console: Specifies the console device.
screen-#columns screen-#rows: If the console is text or graphics type, this parameter sets number of columns and rows of text.

For example, to disable the use of ACPI at boot time, you would edit the $multiboot line as follows. The change is shown in bold.

$multiboot /ROOT/transition/@/$kern $kern -B console=graphics -B $zfs_bootfs -B acpi-user-options=0x2

For accepted values you can specify for these parameters, see the eeprom(8) man page.