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BOOT(8) BSD/i386 System Manager's Manual BOOT(8) NAME boot -- system bootstrapping procedures DESCRIPTION Power fail and crash recovery. Normally, the system will reboot itself at power-up or after crashes. An automatic consistency check of the file systems will be performed, and unless this fails, the system will resume multi-user operations. Cold starts. Most i386 PCs attempt to boot first from floppy disk drive 0 (sometimes known as drive A:) and, failing that, from hard disk drive 0 (sometimes known as drive C:, or as drive 0x80 to the BIOS). Some BIOSes allow you to change this default sequence, and may also include a CD-ROM drive as a boot device. By default, a three-stage bootstrap is employed, and control is automati- cally passed from the boot blocks (bootstrap stages one and two) to a separate third-stage bootstrap program, loader(8). This third stage pro- vides more sophisticated control over the booting process than it is pos- sible to achieve in the boot blocks, which are constrained by occupying limited fixed space on a given disk or slice. However, it is possible to dispense with the third stage altogether, ei- ther by specifying a kernel name in the boot block parameter file, /boot.config, or, unless option -n is set, by hitting a key during a brief pause (while one of the characters -, \, |, or / is displayed) be- fore loader(8) is invoked. Booting will also be attempted at stage two, if the third stage cannot be loaded. The remainder of this subsection deals only with the boot blocks. The loader(8) program is documented separately. After the boot blocks have been loaded, you should see a prompt similar to the following: >> FreeBSD/i386 BOOT Default: 0:ad(0,a)/kernel boot: The automatic boot will attempt to load /kernel from partition `a' of ei- ther the floppy or the hard disk. This boot may be aborted by typing any character on the keyboard at the `boot:' prompt. At this time, the fol- lowing input will be accepted: ? Give a short listing of the files in the root directory of the default boot device, as a hint about available boot files. (A ? may also be specified as the last segment of a path, in which case the listing will be of the relevant subdirectory.) bios_drive:interface(unit,[slice,]part) filename [-aCcDdghmnPprsv] Specify boot file and flags. bios_drive The drive number as recognized by the BIOS. 0 for the first drive, 1 for the second drive, etc. interface The type of controller to boot from. Note that the con- troller is required to have BIOS support since the BIOS services are used to load the boot file image. The supported interfaces are: ad ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike controller fd 5 1/4" or 3 1/2" High density floppies da SCSI disk on any supported SCSI controller unit The unit number of the drive on the interface being used. 0 for the first drive, 1 for the second drive, etc. [slice,]part The partition letter inside the BSD portion of the disk. See disklabel(8). By convention, only partition `a' con- tains a bootable image. If sliced disks are used ("fdisk partitions"), any slice (1 for the first slice, 2 for the second slice, etc.) can be booted from, with the default (if not specified) being the active slice or, otherwise, the first FreeBSD slice. If slice is specified as 0, the first FreeBSD slice (also known as "compatibility" slice) is booted from. filename The pathname of the file to boot (relative to the root directory on the specified partition). Defaults to /kernel. Symbolic links are not supported (hard links are). -aCcDdghmnPprsv Boot flags: -a during kernel initialization, ask for the device to mount as the root file system. -C boot from CDROM. -c run UserConfig to modify hardware parameters for the loaded kernel. If the kernel was built with one of USERCONFIG, INTRO_USERCONFIG, VISUAL_USERCONFIG options, remain in UserConfig re- gardless of any quit commands present in the script. -D toggle single and dual console configurations. In the single configuration the console will be either the internal display or the serial port, depending on the state of the -h option below. In the dual console configuration, both the internal display and the serial port will become the console at the same time, regardless of the state of the -h op- tion. However, the dual console configuration takes effect only during the boot prompt. Once the kernel is loaded, the console specified by the -h option becomes the only console. -d enter the DDB kernel debugger (see ddb(4)) as early as possible in kernel initialization. -g use the GDB remote debugging protocol. -h toggle internal and serial consoles. You can use this to switch console devices. For instance, if you boot from the internal console, you can use the -h option to force the kernel to use the serial port as its console device. Alternatively, if you boot from the serial port, you can use this option to force the kernel to use the internal display as the console instead. The serial port driver sio(4) has a flag to override this option. If that flag is set, the serial port will always be used as the console, regardless of the -h option described here. See the man page for sio(4) for more de- tails. -m mute the console. -n ignore key press to interrupt boot before loader(8) is invoked. -P probe the keyboard. If no keyboard is found, the -D and -h options are automatically set. -p pause after each attached device during the device probing phase. -r use the statically configured default for the de- vice containing the root file system (see config(8)). Normally, the root file system is on the device that the kernel was loaded from. -s boot into single-user mode; if the console is marked as "insecure" (see ttys(5)), the root pass- word must be entered. -v be verbose during device probing (and later). You may put a BIOS drive number, a controller type, a unit number, a par- tition, a kernel file name, and any valid option in /boot.config to set defaults. Enter them in one line just as you type at the `boot:' prompt. FILES /boot.config parameters for the boot blocks (optional) /boot/boot1 first stage bootstrap file /boot/boot2 second stage bootstrap file /boot/loader third stage bootstrap /kernel default kernel /kernel.old typical non-default kernel (optional) SEE ALSO ddb(4), ttys(5), boot0cfg(8), btxld(8), config(8), disklabel(8), halt(8), loader(8), reboot(8), shutdown(8) DIAGNOSTICS When disk-related errors occur, these are reported by the second-stage bootstrap using the same error codes returned by the BIOS, for example "Disk error 0x1 (lba=0x12345678)". Here is a partial list of these error codes: 0x1 Invalid argument 0x2 Address mark not found 0x4 Sector not found 0x8 DMA overrun 0x9 DMA attempt across 64K boundary 0xc Invalid media 0x10 Uncorrectable CRC/ECC error 0x20 Controller failure 0x40 Seek failed 0x80 Timeout NOTE: On older machines, or otherwise where EDD support (disk packet in- terface support) is not available, all boot-related files and structures (including the kernel) that need to be accessed during the boot phase must reside on the disk at or below cylinder 1023 (as the BIOS under- stands the geometry). When a "Disk error 0x1" is reported by the second- stage bootstrap, it generally means that this requirement has not been adhered to. BUGS The disklabel(5) format used by this version of BSD is quite different from that of other architectures. Due to space constraints, the keyboard probe initiated by the -P option is simply a test that the BIOS has detected an "extended" keyboard. If an "XT/AT" keyboard (with no F11 and F12 keys, etc.) is attached, the probe will fail. BSD April 19, 1994 BSD
NAME | DESCRIPTION | FILES | SEE ALSO | DIAGNOSTICS | BUGS
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