README.altboot revision 1.7
1/// notes about altboot /// 2 3$NetBSD: README.altboot,v 1.7 2012/01/01 14:16:41 phx Exp $ 4 5Altboot is a functional bridge to fill the gap between a NAS product 6custom bootloader and the NetBSD kernel startup environment. Altboot 7irons out and rectifies erroneously configured HW by product 8bootloaders and prepares a sane runtime, better suited for booting 9NetBSD 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 20Altboot 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 47The standard use of altboot is to invoke it with a short script from 48U-Boot/PPCboot, where the altboot.bin image is stored in an unoccupied 128KB 49section of the target's HW NOR flash. Combined with standard 50U-Boot/PPCboot functions, it is possible to boot a NetBSD kernel off 51it right after power-on, without the help of manual intervention. Note 52that the original U-Boot/PPCboot still remains useful and altboot works 53as a functional extension for them. 54 55In case the firmware was crippled by the vendor so that it only boots 56Linux U-Boot images (D-Link), you can still use altboot by uploading 57altboot.img instead of the Linux kernel. 58 59Altboot passes the following bootinfo records to the NetBSD/sandpoint 60kernel. 61- processor clock tick value driving MPC8241/8245. 62- serial console selection. 63- booted kernel filename and which device it was fetched from. 64- Ethernet MAC address, if target HW lacks SEEPROM to store a unit unique 65 value. 66- product family indication. 67- preloaded kernel module names (under development). 68 69When no arguments are given, altboot defaults to boot a kernel called 70"netbsd" from the root partition of the first disk in multiuser mode. 71 72Boot arguments may be passed in three ways: 73- On the command line, directly after the "go 0x1000000" command. 74- From the U-Boot "bootargs" environment variable, when started by "bootm". 75- By entering the interactive mode. 76 77The following boot arguments are recognized: 78- multi boot into multiuser 79- auto boot into multiuser 80- single boot into singleuser 81- ask ask for boot device 82- ddb drop into the kernel debugger 83- userconf change configured devices 84 85The following boot flags are recognized: 86- norm boot normally 87- quiet boot quietly 88- verb boot verbosely 89- silent boot silently 90- debug boot with debug output 91 92Additionally the special argument "altboot" is recognized, which replaces 93the actually running altboot program with the loaded binary file and 94restarts itself. Mainly useful for altboot testing. 95 96Multiple arguments may be specified at once, although not all combinations 97make sense. The format of an altboot command line is: 98 99 [[<bootargs> ...] <devicename>:[<bootfile>]] 100 101The following device names are supported: 102- tftp boot from TFTP (address retrieved by DHCP) 103- nfs boot from NFS (address retrieved by DHCP) 104- wd[N[P]] boot from disk N, partition P, defaults to wd0a 105- mem boot from memory 106 107For tftp and nfs the bootfile is determined by DHCP, when missing. 108For wd it defaults to "netbsd". 109For mem the bootfile is actually a hexadecimal address to load from and 110is mandatory. 111 112 ### ### ### 113