The Magenta kernel receives a textual commandline from the bootloader, which can be used to alter some behaviours of the system. Kernel commandline parameters are in the form of option or option=value, separated by spaces, and may not contain spaces.
For boolean options, option=0, option=false, or option=off will disable the option. Any other form (option, option=true, option=wheee, etc) will enable it.
The kernel commandline is passed from the kernel to the userboot process and the device manager, so some of the options described below apply to those userspace processes, not the kernel itself.
If this option is set, the system will not use Address Space Layout Randomization.
If this option is set, the crashlogger is not started. You should leave this option off unless you suspect the crashlogger is causing problems.
If this option is set, the crashlogger will attempt to generate a "processor trace" dump along with the crash report. The dump files are written as /tmp/crash-pt.*. This option requires processor tracing to be enabled in the kernel. This can be done by running "ipt" program after the system has booted. E.g., add this to /system/autorun
ipt --circular --control init start
After the files are written, copy them to the host and print them with the "ipt-dump" program. See its docs for more info.
This option is only supported on Intel x86 platforms.
Disables the driver with the given name. The driver name comes from the magenta_driver_info, and can be found as the second argument to the MAGENTA_DRIVER_BEGIN macro.
Example: driver.usb-audio.disable
Provides entropy to be mixed into the kernel's CPRNG.
If this option is set (disabled by default), the system will attempt to detect hangs/crashes and reboot upon detection.
If this option is set (disabled by default), the system will halt on a kernel panic instead of rebooting.
This option tells the kernel to limit system memory to the MB value specified by 'num'. Using this effectively allows a user to simulate the system having less physical memory than physically present.
This option (disabled by default) requests that the kernel start a graphics console during early boot (if possible), to display kernel debug print messages while the system is starting. When userspace starts up, a usermode graphics console driver takes over.
The early kernel console can be slow on some platforms, so if it is not needed for debugging it may speed up boot to disable it.
This option asks the graphics console to use a specific font. Currently only "9x16" (the default) and "18x32" (a double-size font) are supported.
Do not launch the virtual console service if this option is present.
If this option is present, the virtual console service will keep the debug log (vc0) visible instead of switching to the first shell (vc1) at startup.
Specify the keymap for the virtual console. "qwerty" and "dvorak" are supported.
Specify the font for the virtual console. "9x16" and "18x32" are supported.
This option specifies the size of the buffer for ktrace records, in megabytes. The default is 32MB.
This option specifies what ktrace records are emitted. The value is a bitmask of KTRACE_GRP_* values from magenta/ktrace.h. Hex values may be specified as 0xNNN.
This option (disabled by default) turns on dynamic linker trace output. The output is in a form that is consumable by clients like Intel Processor Trace support.
This option requests that the executable at path be launched at boot, after devmgr starts up.
This option requests that the executable at path be launched once the system partition is mounted and init is launched. If there is no system bootfs or system partition, it will never be launched.
This option caps the number of CPUs to initialize. It cannot be greater than SMP_MAX_CPUS for a specific architecture.
This option can be used to disable the initialization of hyperthread logical CPUs. Defaults to true.
If this option is set, devmgr will not activate the first interactive console. It is useful for scenarios in which user input handling (and the ability to switch vcs) is not available. Defaults to false.
This option can be used to force the selection of a particular wall clock. It only is used on pc builds. Options are "tsc", "hpet", and "pit".
This option instructs the userboot process (the first userspace process) to execute the specified binary within the bootfs, instead of following the normal userspace startup process (launching the device manager, etc).
It is useful for alternate boot modes (like a factory test or system unit tests).
The pathname used here is relative to /boot, so it should not start with
a / prefix.
Note that this option does not work for executables that are linked with libraries other than libc and the dynamic linker.
Example: userboot=bin/core-tests
If this option is set, userboot will attempt to power off the machine when the process it launches exits.
If this option is set, the mx_ticks_get and mx_ticks_per_second system
calls will use mx_time_get(MX_CLOCK_MONOTONIC) in nanoseconds rather than
hardware cycle counters in a hardware-based time unit. Defaults to false.
This option sets the boot timeout in the bootloader, with a default of 3 seconds. Set to zero to skip the boot menu.
This option sets the framebuffer resolution. Use the bootloader menu to display available resolutions for the device.
Example: bootloader.fbres=640x480
This option sets the default boot device to netboot or local magenta.bin.
Pass each option using -c, for example:
./scripts/run-magenta-x86-64 -c gfxconsole.font=18x32 -c gfxconsole.early=false
Pass the kernel commandline at the end, after a -- separator, for example:
bootserver magenta.bin bootfs.bin -- gfxconsole.font=18x32 gfxconsole.early=false
Create a text file named "cmdline" in the root of the USB flash drive's filesystem containing the command line.