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LOADER(8) System Manager's Manual LOADER(8) NAME loader -- kernel bootstrapping final stage DESCRIPTION The program called loader is the final stage of FreeBSD's kernel boot- strapping process. It is responsible for bringing the kernel, kernel modules and other files into memory. It creates a set of sh(1) like environment variables that are passed to the kernel. It executes boot scripts written in one of several interpreters. Together with the scripts, it controls the booting process and interaction with the user. It provides a scripting language that can be used to automate tasks, do pre-configuration or assist in recovery procedures. This scripting language is roughly divided in two main components. The smaller one is a set of commands designed for direct use by the casual user, called "builtin commands" for historical reasons. The main drive behind these commands is user-friendliness. The larger component is the scripting language built into the boot loader. FreeBSD provides three different interpreters: Forth, Lua and Simple. The Forth loader is based on an ANS Forth compatible Forth interpreter based on FICL, by John Sadler. The Lua loader is a full Lua interpreter from https://www.lua.org/. The Simple loader only interprets a list of builtin commands without any control structure. During initialization, loader will probe for a console and set the console variable, or set it to serial console ("comconsole") if the previous boot stage used that. If multiple consoles are selected, they will be listed separated by spaces. Then, devices are probed, currdev and loaddev are set, and LINES is set to 24. Finally, an interpreter specific file will be executed. BUILTIN COMMANDS The commands common to all interpreters are described in the loader_simp(8) "BUILTIN COMMANDS" section. The following commands are only available in loader_lua(8) and loader_4th(8): boot-conf Load the loader config and commence the autoboot sequence. read-conf file Load the specified configuration file. reload-conf Revert any previously applied settings, and reload the configu- ration. Set comands that were executed at the command line to override variables previously set by loader.conf(5) configura- tion will also be reverted, along with any module options that were toggled. enable-module kmod-name disable-module kmod-name toggle-module kmod-name Enable, disable, or toggle loading of the kernel module named "kmod-name". show-module-options Describe all modules the loader is aware of, and show if they are enabled or not. The following command is only available in loader_lua(8): disable-device device Set a newbus hint to disable the device. BUILTIN ENVIRONMENT VARIABLES The environment variables common to all interpreters are described in the loader_simp(8) "BUILTIN ENVIRONMENT VARIABLES" section. SEE ALSO libsa(3), loader.conf(5), tuning(7), boot(8), btxld(8), loader.efi(8), loader_4th(8), loader_lua(8), loader_simp(8) HISTORY The loader first appeared in FreeBSD 3.1. The loader scripting lan- guage changed to Lua by default in FreeBSD 12.0. AUTHORS The loader was written by Michael Smith <msmith@FreeBSD.org>. FICL was written by John Sadler <john_sadler@alum.mit.edu>. Warner Losh <imp@FreeBSD.org> integrated Lua into the tree based on initial work done by Pedro Souza for the 2014 Google Summer of Code. FreeBSD 15.0 November 14, 2025 LOADER(8)
NAME | DESCRIPTION | BUILTIN COMMANDS | SEE ALSO | HISTORY | AUTHORS
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