9boot man page on Plan9

Man page or keyword search:  
man Server   549 pages
apropos Keyword Search (all sections)
Output format
Plan9 logo
[printable version]

9BOOT(8)							      9BOOT(8)

       9boot, 9bootpbs, 9load, 9loadusb, pbs - PC bootstrap programs


       9boot  is  a  specialized  Plan	9  kernel  loaded  by the PXE download
       (BOOTP/DHCP followed by TFTP) found in any reasonable  Ethernet	card's
       BIOS;  it  bootstraps  Plan 9 by using PXE to load another 386 or amd64
       kernel and start it.

       9bootpbs, 9load	and  9loadusb  are  less-commonly-used	variants  that
       reside  in  a  FAT  file	 system	 under	the name and bootstrap Plan 9.
       9bootpbs is like 9boot but it can be started by a partition boot sector
       (PBS),  as  can	9load  and 9loadusb.  It is intended to PXE boot older
       machines without working PXE ROMs.  9load and 9loadusb  read  FAT  file
       systems.	  9loadusb  will  use only the BIOS's device drivers, and thus
       can load from FAT file systems on USB devices.  In contrast, 9load will
       not use BIOS device drivers and cannot read USB devices.

       This  profusion	of  loaders is unfortunate, but at least they are com‐
       piled from the same source.  The division  into	separate  programs  is
       dictated	 by  the  need	to fit within the first 640K of memory and the
       need to avoid intermixing BIOS and non-BIOS disk access.

       These programs are run automatically by the boot	 procedures  described
       below;  they  cannot  be run directly by hand.  There are two bootstrap

       -  PXE BIOS, 9boot, kernel

       -  BIOS, MBR, disk partition PBS, 9load, kernel

       In summary, Plan 9 is usually booted on a PC  by	 using	a  PXE-capable
       BIOS  to boot 9boot directly over the ethernet.	File servers that must
       be able to boot when other machines are down boot directly from a  Plan
       9 disk partition prepared using format to install the appropriate files
       and bootstrap sectors (see prep(8)).

       Details follow.

   Kernel loading
       9boot is a bootstrap program that loads and starts a program, typically
       the  kernel,  on	 a  PC.	  It is run by the PXE boot ROM of a PC, which
       loads 9boot at physical address 0x7C00 (31K).  When it starts  running,
       it  switches  to	 32-bit	 mode.	 It then double maps the first 16Mb of
       physical memory to virtual addresses 0 and  0x80000000.	 Only  devices
       which can be automatically configured, e.g. most PCI ethernet adapters,
       will be recognised.  If the file /cfg/pxe/ether can be  located	via  a
       DHCP  server, where ether is the lower-case MAC address of a recognised
       ethernet adapter, the contents are obtained  by	TFTP  and  used	 as  a
       plan9.ini(8).   9boot  then  loads  the bootfile named within via TFTP,
       trying each ethernet in sequence, at the entry address specified by the
       kernel executable's header, usually virtual 0xF0100020.	After loading,
       9boot creates a Gnu Multiboot header in low memory for the  benefit  of
       the loaded kernel and control is passed to the entry location in 32-bit
       protected mode, even for 64-bit kernels.	 So far,  only	amd64  kernels
       expect Multiboot headers.

       Some options in plan9.ini are used by 9boot:


       baud   Specifies the console device and baud rate if not a display.

       ethern Ethernet interfaces. These can be used to load the bootfile over
	      a network.

	      Specifies the bootfile.

	      After determining which devices are available for loading	 from,
	      enter prompt mode.

       9load  is  a similar bootstrap program, loaded by the PC partition boot
       sector program (PBS), which usually resides in the first sector of  the
       active  disk  partition.	  It  is  initially loaded at physical address
       0x10000(64K); it begins execution at virtual  address  0x80010000.   In
       order  to  find	configuration information, 9load searches all units on
       devices sd?[0-9]* (all sd devices), for a file  called  plan9.ini  (see
       plan9.ini(8))  on  a FAT partition named dos or 9fat.  If one is found,
       searching stops and the file is read into memory	 at  physical  address
       0x1200 where it can be found later by any loaded bootfile.

       When  the  search  for  plan9.ini  is done, 9load proceeds to determine
       which bootfile to  load.	  If  there  was  no  bootfile	option,	 9load
       searches	 sd?[0-9]*  FAT	 partitions for a kernel (any file named 9pc*,
       9k8* or 9k10*) and if it finds exactly one kernel in a given FAT parti‐
       tion, chooses it.  9load then attempts to load the bootfile.

       9load  prints  the  list of available devices and enters prompt mode on
       encountering any error or if directed to do  so	by  a  bootfile=manual
       option.	 In  prompt  mode,  the user is required to type a bootfile in
       response to the prompt.

       The bootfile can be specified to these programs as a bootfile= entry in
       plan9.ini, or if booting from the ethernet, by a BOOTP server (see Ker‐
       nel loading below).  If loading with 9load, the bootfile may be a  Plan
       9  boot	image compressed with gzip(1).	In all cases, the uncompressed
       kernel must be in Plan 9 boot image,  ELF  or  ELF64  format.   If  the
       plan9.ini file contains multiple bootfile= entries, these programs will
       present a numerical menu of the choices; type the corresponding	number
       to select an entry.

       The  format  of	the  bootfile  name  is	 device!file  or device!parti‐
       tion!file.  If !file is omitted, the default for the particular	device
       is used.	 Supported devices are

       ethern Ethernet,	 9boot	only.  N specifies the Ethernet device number.
	      If a partition is specified, it is taken to be  the  name	 of  a
	      host machine from which to load the kernel.

       sdCn   Normal disk, 9load only.	The device name format is described in
	      sd(3).  A partition must be given and must normally name a  par‐
	      tition  containing  a  FAT file system.  It is common for Plan 9
	      partitions to contain a small FAT file system for configuration.
	      By  convention,  this  partition	is  called  9fat.  There is no
	      default partition, but if file is omitted,  9load	 will  load  a
	      kernel directly from the named partition without any interpreta‐
	      tion of a file system.

       biosn  USB or other BIOS device, 9loadusb only.	9load loads from a FAT
	      file  system  on	the  first  LBA	 device	 in the BIOS's list of
	      devices to try to boot from, using the BIOS INT  13  calls  also
	      used  by	pbslba.	  It does not understand any form of partition
	      table; see the EXAMPLES in prep(8) for  how  to  format  such  a

       sdBn   USB  or other BIOS device's partition, 9loadusb only.  A special
	      case of sdCn that uses biosn to read from a FAT file system.

   Boot Sectors
       A copy of the Plan 9 PBS is kept in /386/pbs, but due to	 the  ``cylin‐
       der-head-sector''  (CHS)	 addressing  mode  of  old BIOSes, it can only
       operate up to 8.5GB into the disk.  Plan 9 partitions further into  the
       disk  can  only	be  booted  using  /386/pbslba,	 and  then only if the
       machine's BIOS supports linear block addressing	(LBA)  mode  for  disk

       When  booting  from disk, the BIOS loads the first sector of the medium
       at location 0x7C00.  In the case of a  disk,  it	 is  the  master  boot
       record (MBR).  The MBR copies itself to address 0x600, finds the active
       partition and loads its PBS at address 0x7C00.  A copy of  the  Plan  9
       MBR  is kept in /386/mbr; some commercial MBRs cannot read sectors past
       2GB.  The Plan 9 MBR can read sectors up to 8.5GB into  the  disk,  and
       further	if  the	 BIOS  supports LBA.  The single file /386/mbr detects
       whether the BIOS supports LBA and acts appropriately, defaulting to CHS
       mode when LBA is not present.  The PBSs cannot do this due to code size
       limitations.  The Plan 9 MBR is suitable for booting non-Plan-9 operat‐
       ing  systems,  and  (modulo  the large disk constraints just described)
       non-Plan-9 MBRs are suitable for booting Plan 9.

   Other facilities and caveats
       9load parses the master boot record and Plan 9  partition  tables  (see
       prep(8)),  leaving  partitioning	 information appended to the in-memory
       contents of plan9.ini for the bootfile.	This is used by sd(3) to  ini‐
       tialize	partitions so that may be read for NVRAM contents or fossil(4)
       or kfs(4) file systems can be mounted as the root file system.  On  ISO
       9660  CDs, 9load treats the contents of a file named /bootdisk.img as a
       9fat partition, and it is assumed to contain the image of  a  FAT  file
       system.	 A  more extensive partitioning is typically done by fdisk and
       prep as part of termrc or cpurc (see  cpurc(8)).	  9boot	 cannot	 parse
       partition  tables,  as  it  lacks disk drivers, so add to the machine's
       /cfg/pxe file, per plan9.ini(8), if needed.

       A control-P character typed at any time on the console causes 9boot  to
       perform	a  hardware  reset (Ctrl-Alt-Del can also be used on a PC key‐

       9load must be contiguously allocated on the disk.   See	dossrv(4)  for
       information on ensuring this.

       /386   these programs reside here

	      directory of configuration (plan9.ini) files on your TFTP server


	      first-stage disk boot sectors (MBR, PBS)
	      PC-bootstrap-specific source
       /sys/src/9/^(pc port ip)
	      common kernel source

       8l(1),	cons(3),   booting(8),	 dhcpd(8),   fshalt(8),	 mkusbboot(8),
       plan9.ini(8), prep(8)

       Some of the work done by 9boot is duplicated by the loaded kernel,  but
       usually by the same source code.

       bios  and  sdB  usually only work on the first LBA device in the BIOS's
       list of boot devices, if they work at all.

       USB keyboards will only work with 9boot if the  BIOS  emulates  a  PS/2
       keyboard (and that is enabled).

                             _         _         _ 
                            | |       | |       | |     
                            | |       | |       | |     
                         __ | | __ __ | | __ __ | | __  
                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 
More information is available in HTML format for server Plan9

List of man pages available for Plan9

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
Vote for polarhome
Free Shell Accounts :: the biggest list on the net