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README.altboot revision 1.9 
      1 /// notes about altboot ///
      2 
      3 $NetBSD: README.altboot,v 1.9 2012/01/14 22:36:54 phx Exp $
      4 
      5 Altboot is a functional bridge to fill the gap between a NAS product
      6 custom bootloader and the NetBSD kernel startup environment.  Altboot
      7 irons out and rectifies erroneously configured HW by product
      8 bootloaders and prepares a sane runtime, better suited for booting
      9 NetBSD kernels.
     10 
     11 - provides the foundation of a fast NetBSD porting cycle with functionalities
     12   product bootloaders don't have.
     13 - facilitates a flexible and clean NetBSD implementation tailoured
     14   to target HW in detail, minimizing bumpy adjustments and hacks in
     15   locore asm and machdeps in very early kernel startup stage.
     16 - levels out differences among similar-but-not-the-same porting
     17   targets to make it possible having common NetBSD kernels for them.
     18 - builds and hands a bootinfo list to the NetBSD kernel.
     19 
     20 Altboot is known working on at least these models:
     21 
     22 - KuroBox or LinkStation with a popular U-Boot as replacement of
     23   the vendor's proprietary one
     24 
     25    U-Boot 1.1.4 LiSt 2.1.0 (Sep 21 2006 - 00:22:56) LinkStation / KuroBox
     26 
     27 - Synology 101g+ with vendor custom PPCboot
     28 
     29    PPCBoot 2.0.0 (Mar  1 2005 - 15:31:41)
     30 
     31 - Synology 106j, 207, 407e with vendor custom PPCboot
     32 
     33    PPCBoot 2.0.0 (Jan 30 2007 - xx:xx:xx)
     34 
     35 - D-Link DSM-G600 with heavily restricted vendor custom U-Boot
     36 
     37    U-Boot 0.2.0 (May 26 2005 - 19:38:32)
     38 
     39 - QNAP TS-101 (V200) with vendor custom U-Boot
     40 
     41    U-Boot 1.1.2 (Aug 28 2005 - 13:37:25) QNAP System, Inc.
     42 
     43 - Iomega StorCenter with vendor custom U-Boot
     44 
     45    U-Boot 1.0.0 (Sep  2 2005 - 14:49:11)
     46 
     47 - Allnet 6250 and compatible with restricted vendor custom PPCboot
     48 
     49    PPCBoot 2.0.0-A9 (Feb 13 2006 - 14:56:11)
     50 
     51 The standard use of altboot is to invoke it with a short script from
     52 U-Boot/PPCboot, where the altboot.bin image is stored in an unoccupied 128KB
     53 section of the target's HW NOR flash.  Combined with standard
     54 U-Boot/PPCboot functions, it is possible to boot a NetBSD kernel off
     55 it right after power-on, without the help of manual intervention.  Note
     56 that the original U-Boot/PPCboot still remains useful and altboot works
     57 as a functional extension for them.
     58 
     59 In case the firmware was crippled by the vendor so that it only boots
     60 Linux U-Boot images (D-Link), you can still use altboot by uploading
     61 altboot.img instead of the Linux kernel.
     62 
     63 Altboot passes the following bootinfo records to the NetBSD/sandpoint
     64 kernel.
     65 - processor clock tick value driving MPC8241/8245.
     66 - serial console selection.
     67 - booted kernel filename and which device it was fetched from.
     68 - Ethernet MAC address, if target HW lacks SEEPROM to store a unit unique
     69   value.
     70 - product family indication.
     71 - preloaded kernel module names (under development).
     72 
     73 When no arguments are given, altboot defaults to boot a kernel called
     74 "netbsd" from the root partition of the first disk in multiuser mode.
     75 
     76 Boot arguments may be passed in three ways:
     77 - On the command line, directly after the "go 0x1000000" command.
     78 - From the U-Boot "bootargs" environment variable, when started by "bootm".
     79 - By entering the interactive mode.
     80 
     81 The following boot arguments are recognized:
     82 - multi			boot into multiuser
     83 - auto			boot into multiuser
     84 - single		boot into singleuser
     85 - ask			ask for boot device
     86 - ddb			drop into the kernel debugger
     87 - userconf		change configured devices
     88 
     89 The following boot flags are recognized:
     90 - norm			boot normally
     91 - quiet			boot quietly
     92 - verb			boot verbosely
     93 - silent		boot silently
     94 - debug			boot with debug output
     95 
     96 Additionally the special argument "altboot" is recognized, which replaces
     97 the actually running altboot program with the loaded binary file and
     98 restarts itself. Mainly useful for altboot testing.
     99 
    100 Multiple arguments may be specified at once, although not all combinations
    101 make sense. The format of an altboot command line is:
    102 
    103   [[<bootargs> ...] <devicename>:[<bootfile>]]
    104 
    105 The following device names are supported:
    106 - tftp			boot from TFTP (address retrieved by DHCP)
    107 - nfs			boot from NFS (address retrieved by DHCP)
    108 - wd[N[P]]		boot from disk N, partition P, defaults to wd0a
    109 - mem			boot from memory
    110 
    111 For tftp and nfs the bootfile is determined by DHCP, when missing.
    112 For wd it defaults to "netbsd".
    113 For mem the bootfile is actually a hexadecimal address to load from and
    114 is mandatory.
    115 
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