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LOADER.CONF(5) File Formats Manual LOADER.CONF(5)

loader.conf — system bootstrap configuration information

The file loader.conf contains descriptive information on bootstrapping the system. Through it you can specify the kernel to be booted, parameters to be passed to it, and additional modules to be loaded; and generally set all variables described in loader(8).

Though loader.conf's format was defined explicitly to resemble rc.conf(5), and can be sourced by sh(1), some settings are treated in a special fashion. Also, the behavior of some settings is defined by the setting's suffix; the prefix identifies which module the setting controls.

The general parsing rules are:

All settings have the following format:

variable="value"

Unless it belongs to one of the classes of settings that receive special treatment, a setting will set the value of a loader(8) environment variable. The settings that receive special treatment are listed below. Settings beginning with "*" below define the modules to be loaded and may have any prefix; the prefix identifies a module. All such settings sharing a common prefix refer to the same module.

exec
Immediately executes a loader(8) command. This type of setting cannot be processed by programs other than loader(8), so its use should be avoided. Multiple instances of it will be processed independently.
loader_conf_files
Defines additional configuration files to be processed right after the present file.
kernel
Name of the kernel to be loaded. If no kernel name is set, no additional modules will be loaded. The name must be a subdirectory of /boot that contains a kernel.
kernel_options
Flags to be passed to the kernel.
vfs.root.mountfrom
Specify the root partition to mount. For example:

vfs.root.mountfrom="ufs:/dev/da0s1a"

loader(8) automatically calculates the value of this tunable from /etc/fstab from the partition the kernel was loaded from. The calculated value might be calculated incorrectly when /etc/fstab is not available during loader(8) startup (as during diskless booting from NFS), or if a different device is desired by the user. The preferred value can be set in /loader.conf.

The value can also be overridden from the loader(8) command line. This is useful for system recovery when /etc/fstab is damaged, lost, or read from the wrong partition.

password
Protect boot menu with a password without interrupting autoboot process. The password should be in clear text format. If a password is set, boot menu will not appear until any key is pressed during countdown period specified by autoboot_delay variable or autoboot process fails. In both cases user should provide specified password to be able to access boot menu.
bootlock_password
Provides a password to be required by check-password before execution is allowed to continue. The password should be in clear text format. If a password is set, the user must provide specified password to boot.
verbose_loading
If set to “YES”, module names will be displayed as they are loaded.
module_blacklist
Blacklist of modules. Modules specified in the blacklist may not be loaded automatically with a *_load directive, but they may be loaded directly at the loader(8) prompt. Blacklisted modules may still be loaded indirectly as dependencies of other modules.
*_load
If set to “YES”, that module will be loaded. If no name is defined (see below), the module's name is taken to be the same as the prefix.
*_name
Defines the name of the module.
*_type
Defines the module's type. If none is given, it defaults to a kld module.
*_flags
Flags and parameters to be passed to the module.
*_before
Commands to be executed before the module is loaded. Use of this setting should be avoided.
*_after
Commands to be executed after the module is loaded. Use of this setting should be avoided.
*_error
Commands to be executed if the loading of a module fails. Except for the special value “abort”, which aborts the bootstrap process, use of this setting should be avoided.

developers should never use these suffixes for any kernel environment variables (tunables) or conflicts will result.

Most of loader.conf's default settings can be ignored. The few of them which are important or useful are:

bitmap_load
(“NO”) If set to “YES”, a bitmap will be loaded to be displayed on screen while booting.
bitmap_name
(“/boot/splash.bmp”) Name of the bitmap to be loaded. Any other name can be used.
comconsole_speed
(“9600” or the value of the BOOT_COMCONSOLE_SPEED variable when loader(8) was compiled). Sets the speed of the serial console. If the previous boot loader stage specified that a serial console is in use then the default speed is determined from the current serial port speed setting.
console
(“vidconsole”) “comconsole” selects serial console, “vidconsole” selects the video console, “nullconsole” selects a mute console (useful for systems with neither a video console nor a serial port), and “spinconsole” selects the video console which prevents any input and hides all output replacing it with “spinning” character (useful for embedded products and such).
efi_max_resolution
Specify the maximum desired resolution for the EFI console. The following values are accepted:
480p 640x480
720p 1280x720
1080p 1920x1080
2160p 3840x2160
4k 3840x2160
5k 5120x2880
WidthxHeight WidthxHeight
kernel
(“kernel”)
kernels
(“kernel kernel.old”) Space or comma separated list of kernels to present in the boot menu.
loader_conf_files
(“/boot/loader.conf /boot/loader.conf.local”)
splash_bmp_load
(“NO”) If set to “YES”, will load the splash screen module, making it possible to display a bmp image on the screen while booting.
splash_pcx_load
(“NO”) If set to “YES”, will load the splash screen module, making it possible to display a pcx image on the screen while booting.
vesa_load
(“NO”) If set to “YES”, the vesa module will be loaded, enabling bitmaps above VGA resolution to be displayed.
beastie_disable
If set to “YES”, the beastie boot menu will be skipped.
Selects a desired logo in the beastie boot menu. Possible values are: “orbbw”, “orb”, “fbsdbw”, “beastiebw”, “beastie”, and “none”.
loader_color
If set to “NO”, the beastie boot menu will be displayed without ANSI coloring.
entropy_cache_load
(“YES”) If set to “NO”, the very early boot-time entropy file will not be loaded. See the entropy entries in rc.conf(5).
entropy_cache_name
(“/boot/entropy”) The name of the very early boot-time entropy cache file.
cpu_microcode_load
(“NO”) If set to “YES”, the microcode update file specified by cpu_microcode_name will be loaded and applied very early during boot. This provides functionality similar to cpucontrol(8) but ensures that CPU features enabled by microcode updates can be used by the kernel. The update will be re-applied automatically when resuming from an ACPI sleep state. If the update file contains updates for multiple processor models, the kernel will search for and extract a matching update. Currently this setting is supported only on Intel i386 and amd64 processors. It has no effect on other processor types.
cpu_microcode_name
A path to a microcode update file.

Other settings that may be used in loader.conf that have no default value:

fdt_overlays
Specifies a comma-delimited list of FDT overlays to apply. /boot/dtb/overlays is created by default for overlays to be placed in.
kernels_autodetect
If set to “YES”, attempt to auto-detect kernels installed in /boot. This is an option specific to the Lua-based loader. It is not available in the default Forth-based loader.

/boot/defaults/loader.conf
default settings -- do not change this file.
/boot/loader.conf
user defined settings.
/boot/loader.conf.local
machine-specific settings for sites with a common loader.conf.

rc.conf(5), boot(8), cpucontrol(8), loader(8), loader.4th(8)

The file loader.conf first appeared in FreeBSD 3.2.

This manual page was written by Daniel C. Sobral ⟨dcs@FreeBSD.org⟩.

The loader(8) stops reading loader.conf when it encounters a syntax error, so any options which are vital for booting a particular system (i.e. “hw.ata.ata_dma=0”) should precede any experimental additions to loader.conf.

October 6, 2018 FreeBSD-12.0