boot 8 system administrator's manual FreeBSD boot system bootstrapping procedures What happens at power-on, as the result of a cold start or when power is restored after a power failure, is determined by the machine firmware. Normally, the firmware is configured to begin bootstrapping an operating system, although some hardware platforms have the option to not automatically begin bootstrap after power comes on, requiring that the operator explicitly press a power button. If that operating system is FreeBSD, the system performs automatic checks of the filesystem and begins multi-user operations. A similar bootstrap process is followed by a warm start, after a commanded reboot or a system crash. Modern systems have UEFI firmware, and the firmware itself finds, loads, and runs the first FreeBSD program, loader.efi8, usually stored alongside other loaders for other systems and other firmware‐specific programs on a dedicated UEFI disc partition (the EFI System Partition), as detailed in full in uefi8. Such systems encompass PC systems where the UEFI firmware is in non‐volatile memory and SOC machines where the machine bootstrap loads and runs TianoCore from mass storage. The gptboot.efi8 program might be used in place of loader.efi8. Instead of relying upon normal UEFI native configuration, where the UEFI boot manager is configured with both the location of the loader and what FreeBSD kernel to tell the loader to load, it mimics the gptboot8 program (used on old PC firmware), finding, loading, and running a loader from a UFS (only) FreeBSD partition that has been marked in the partition table. Old Intel Architecture (i386 and amd64) PC systems have BIOS firmware, and the firmware loads and runs the code stored in the first sector of a removable or a fixed disc device. This code may be FreeBSD‐supplied, in which case the system runs a FreeBSD‐supplied bootstrap program whose exact nature varies according to whether the disc is a non‐partitioned or a partitioned disc, and the partitioning scheme used on the latter. On partitioned discs, a chain of various programs is run, beginning with the program in that first sector. The chain varies according to the partitioning scheme used on the disc. The full details are in the "BOOTSTRAPPING" section of gpart8. The culmination is loading and running a loader8 program from a UFS or ZFS partition or disc slice. On non‐partitioned discs, or on partitioned discs where a bsdlabel8 is used, the procedure followed is described in boot_i3868. The culmination is, again, loading and running a loader8 program from the disc. If the code is non‐FreeBSD‐supplied, some unspecified chain of third‐party boot managers and boot loaders ends up loading and running the first sector of a FreeBSD disc partition, which then enters the boot_i3868 procedure at stage 1. Bootstrapping from CD-ROM with old PC firmware is done via the cdboot8 program. This manual page used to be an alias for the boot_i3868 manual page. There used to be a boot1.efi8 program that loaded loader.efi8. The UEFI firmware now runs the latter directly. loader.efi8 loader program that uses UEFI‐supplied services to load the FreeBSD kernel proper loader8 loader program that uses old PC firmware‐supplied services to load the FreeBSD kernel proper gptboot8 program which is stored in a dedicated GPT disc partition, that uses old PC firmware‐supplied services to find, load, and run loader8 from another GPT partition containing FreeBSD on UFS gptzfsboot8 program which is stored in a dedicated GPT disc partition, that uses old PC firmware‐supplied services to find, load, and run loader8 from another GPT partition containing FreeBSD on ZFS Jonathande Boyne Pollard