Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

BOOT(8)                     System Manager's Manual                    BOOT(8)

     boot - system bootstrapping procedures

     This document provides information on using common features in the NetBSD
     boot loader.  Additional information may be found in architecture-
     specific boot(8) manual pages.

   Boot Protocol
     In the native NetBSD boot protocol, options are passed from the boot
     loader to the kernel via flag bits in the boothowto variable (see
     boothowto(9)).  Some boot loaders may also support other boot protocols.

     Some boot loaders may present a menu, which may be configured via

   Interactive mode
     In interactive mode, the boot loader will present a prompt, allowing
     input of these commands:

         boot [device:][filename] [-1234abcdmqsvxz]
               The default device will be set to the disk that the boot loader
               was loaded from.  To boot from an alternate disk, the full name
               of the device should be given at the prompt.  device is of the
               form xd [N[x]] where xd is the device from which to boot, N is
               the unit number, and x is the partition letter.

               The following list of supported devices may vary from
               installation to installation:

               hd      Hard disks.
               fd      Floppy drives.

               The default filename is netbsd; if the boot loader fails to
               successfully open that image, it then tries netbsd.gz (expected
               to be a kernel image compressed by gzip), followed by
               netbsd.old, netbsd.old.gz, onetbsd, and finally onetbsd.gz.
               Alternate system images can be loaded by just specifying the
               name of the image.

               Options are:

               -1   Sets the machine-dependent flag RB_MD1 in boothowto.

               -2   Sets the machine-dependent flag RB_MD2 in boothowto.

               -3   Sets the machine-dependent flag RB_MD3 in boothowto.

               -4   Sets the machine-dependent flag RB_MD4 in boothowto.

               -a   Sets the RB_ASKNAME flag in boothowto.  This causes the
                    kernel to prompt for the root file system device, the
                    system crash dump device, and the path to init(8).

               -b   Sets the RB_HALT flag in boothowto.  This causes
                    subsequent reboot attempts to halt instead of rebooting.

               -c   Sets the RB_USERCONF flag in boothowto.  This causes the
                    kernel to enter the userconf(4) device configuration
                    manager as soon as possible during the boot.  userconf(4)
                    allows devices to be enabled or disabled, and allows
                    device locators (such as hardware addresses or bus
                    numbers) to be modified before the kernel attempts to
                    attach the devices.

               -d   Sets the RB_KDB flag in boothowto.  Requests the kernel to
                    enter debug mode, in which it waits for a connection from
                    a kernel debugger; see ddb(4).

               -m   Sets the RB_MINIROOT flag in boothowto.  Informs the
                    kernel that a mini-root file system is present in memory.

               -q   Sets the AB_QUIET flag in boothowto.  Boot the system in
                    quiet mode.

               -s   Sets the RB_SINGLE flag in boothowto.  Boot the system in
                    single-user mode.

               -v   Sets the AB_VERBOSE flag in boothowto.  Boot the system in
                    verbose mode.

               -x   Sets the AB_DEBUG flag in boothowto.  Boot the system with
                    debug messages enabled.

               -z   Sets the AB_SILENT flag in boothowto.  Boot the system in
                    silent mode.

         consdev dev
               Immediately switch the console to the specified device dev and
               reprint the banner.  dev must be one of pc, com0, com1, com2,
               com3, com0kbd, com1kbd, com2kbd, com3kbd, or auto.  See Console
               Selection Policy in x86/boot_console(8).

         dev [device]
               Set the default drive and partition for subsequent filesystem
               operations.  Without an argument, print the current setting.
               device is of the form specified in boot.

         help  Print an overview about commands and arguments.

         ls [path]
               Print a directory listing of path, containing inode number,
               filename, and file type.  path can contain a device

         quit  Reboot the system.

     In an emergency, the bootstrap methods described in the NetBSD
     installation notes for the specific architecture can be used.

     /boot                    boot program code loaded by the primary
     /netbsd                  system code
     /netbsd.gz               gzip-compressed system code
     /usr/mdec/boot           master copy of the boot program (copy to /boot)
     /usr/mdec/bootxx_fstype  primary bootstrap for filesystem type fstype,
                              copied to the start of the NetBSD partition by

     Architecture-specific boot(8) manual pages (such as emips/boot(8),
     sparc64/boot(8), x86/boot(8)), ddb(4), userconf(4), halt(8),
     installboot(8), reboot(8), rescue(8), shutdown(8), boothowto(9)

     The kernel file name must be specified before, not after, the boot
     options.  Any filename specified after the boot options, e.g.:

           boot -d netbsd.test

     is ignored, and the default kernel is booted.

NetBSD 9.99                     August 16, 2014                    NetBSD 9.99