Matthew(黑夜编码人) <matthew@cnfug.org>
前言
在前面我们已经讲过如何制作软盘上运行的FreeBSD和OpenBSD系统，现在我们来看看如何制作一个运行在软盘上的NetBSD系统。同软盘中的OpenBSD系统一样，我们还是将系统中的所有配制文件及程序全部存放到NetBSD的内核中，这样整个系统看起来就是一个文件。下面让我们具体来看看如何完成这样一个微系统的制作。
0、NetBSD的启动过程
当硬盘MBR中的引导程序接过启动之后，MBR中的程序将读入硬盘NetBSD分区中的引导程序，引导程序默认情况下会加载/boot，然后由boot载入内核/netbsd，此时内核开始检测一些硬件和做一些初始化。初始化完成后kernel将mount root device，然后启动系统初始化进程/sbin/init，init将根据/etc/rc中的设置来进行初始化等。
1、定制RAMDISK内核
要使用RAMDISK in KERNEL就必须在内核配制文件中加入以下选项：options MEMORY_DISK_HOOKSoptions MEMORY_DISK_IS_ROOT # force root on memory diskoptions MEMORY_DISK_SERVER=0options MEMORY_DISK_ROOT_SIZE=10000 # size of memory disk, in blocksoptions MEMORY_RBFLAGS=0x00 # boot in to multi-user modepseudo-device md 1 # memory disk device (ramdisk)
以上的内核参数意义如下：
MEMORY_DISK_ROOT_SIZE : 内存磁盘大小，以块为单位MEMORY_RBFLAGS=0x00 : 启动到多用户模式
以下是在我机器上使用的一个内核配制文件include "arch/i386/conf/std.i386"
#options INCLUDE_CONFIG_FILE # embed config file in kernel binary
makeoptions COPTS="-Os" # Optimise for space. Implies -O2
# Enable the hooks used for initializing the root memory-disk.options MEMORY_DISK_HOOKSoptions MEMORY_DISK_IS_ROOT # force root on memory diskoptions MEMORY_DISK_SERVER=1 # 0 readonly 1 writableoptions MEMORY_DISK_ROOT_SIZE=10000 # size of memory disk, in blocksoptions MEMORY_RBFLAGS=0x00 # boot in to multi-user mode
maxusers 48 # estimated number of users
# CPU support. At least one is REQUIRED.options I386_CPUoptions I686_CPU
# CPU-related options.options MATH_EMULATE # floating point emulation
# This option allows you to force a serial console at the specified# I/O address.#options CONSDEVNAME=""com"",CONADDR=0x3f8,CONSPEED=9600
# Avoid irq 5 and 7, the most likely cause of problems on modern laptops.options PCIC_ISA_INTR_ALLOC_MASK=0xff5f
# Standard system options
options INSECURE # disable kernel security levels
options RTC_OFFSET=0 # hardware clock is this many mins. west of GMT#options NTP # NTP phase/frequency locked loop
options USERCONF # userconf(4) supportoptions PIPE_SOCKETPAIR # smaller, but slower pipe(2)options MALLOC_NOINLINE # Not inlining MALLOC saves memory
# File systemsfile-system FFS # UFSfile-system MFS # memory file systemfile-system MSDOSFS # MS-DOS file systemfile-system KERNFS # /kern
options VNODE_OP_NOINLINE # Not inlining vnode op calls saves mem
# Networking optionsoptions GATEWAY # packet forwardingoptions INET # IP + ICMP + TCP + UDP#options PFIL_HOOKS # pfil(9) packet filter hooks
# builtin terminal emulationsoptions WSEMUL_VT100 # VT100 / VT220 emulation# different kernel output - see dev/wscons/wsdisplayvar.hoptions WS_KERNEL_FG=WSCOL_BLACKoptions WS_KERNEL_BG=WSCOL_WHITE# compatibility to other console drivers#options WSDISPLAY_COMPAT_PCVT # emulate some ioctls#options WSDISPLAY_COMPAT_SYSCONS # emulate some ioctls#options WSDISPLAY_COMPAT_USL # VT handling#options WSDISPLAY_COMPAT_RAWKBD # can get raw scancodes# see dev/pckbc/wskbdmap_mfii.c for implemented layouts#options PCKBD_LAYOUT="(KB_DE | KB_NODEAD)"# allocate a number of virtual screens at autoconfiguration time#options WSDISPLAY_DEFAULTSCREENS=4# use a large software cursor that doesn't blinkoptions PCDISPLAY_SOFTCURSOR# modify the screen type of the console; defaults to "80x25"#options VGA_CONSOLE_SCREENTYPE=""80x24""
# Kernel root file system and dump configuration.config netbsd root on ? type ?#config netbsd root on sd0a type ffs#config netbsd root on ? type nfs
## Device configuration#
mainbus0 at root
cpu* at mainbus?
apm0 at mainbus0 # Advanced power management
# Basic Bus Support
# PCI bus supportpci* at mainbus? bus ?pci* at pchb? bus ?pci* at ppb? bus ?
# PCI bridgespchb* at pci? dev ? function ? # PCI-Host bridgespceb* at pci? dev ? function ? # PCI-EISA bridgespcib* at pci? dev ? function ? # PCI-ISA bridgesppb* at pci? dev ? function ? # PCI-PCI bridges# XXX 'puc's aren't really bridges, but there's no better place for them herepuc* at pci? dev ? function ? # PCI "universal" comm. cards
# ISA bus supportisa0 at mainbus?isa0 at pceb?isa0 at pcib?
# ISA Plug-and-Play bus supportisapnp0 at isa?
# Coprocessor Support
# Math Coprocessor supportnpx0 at isa? port 0xf0 irq 13 # x86 math coprocessor
# Console Devices
# ISA console#pc0 at isa? port 0x60 irq 1 # pccons generic PC console driver
# wsconspckbc0 at isa? # pc keyboard controllerpckbd* at pckbc? # PC keyboard#pms* at pckbc? # PS/2 mouse for wsmousevga0 at isa?vga* at pci? dev ? function ?pcdisplay0 at isa? # CGA, MDA, EGA, HGAwsdisplay* at vga? console ?wsdisplay* at pcdisplay? console ?wskbd* at pckbd? console ?#wsmouse* at pms? mux 0
pcppi0 at isa?sysbeep0 at pcppi?
# Serial Devices
# PCI serial interfacescom* at puc? port ? # 16x50s on "universal" comm boards#cy* at pci? dev ? function ? # Cyclades Cyclom-Y serial boards
# ISA Plug-and-Play serial interfacescom* at isapnp? # Modems and serial boards
# ISA serial interfaces#options COM_HAYESP # adds Hayes ESP serial board supportcom0 at isa? port 0x3f8 irq 4 # Standard PC serial portscom1 at isa? port 0x2f8 irq 3com2 at isa? port 0x3e8 irq 5#com3 at isa? port 0x2e8 irq 9#ast0 at isa? port 0x1a0 irq 5 # AST 4-port serial cards#com* at ast? slave ?#boca0 at isa? port 0x100 irq 5 # BOCA 8-port serial cards#com* at boca? slave ?#tcom0 at isa? port 0x100 irq 7 # TC-800 8-port serial cards#com* at tcom? slave ?#rtfps0 at isa? port 0x1230 irq 10 # RT 4-port serial cards#com* at rtfps? slave ?#cy0 at isa? iomem 0xd4000 irq 12 # Cyclades serial cards
# Miscellaneous mass storage devices
# Network Interfaces
# PCI network interfacesfxp* at pci? dev ? function ? # Intel EtherExpress PRO 10+/100Ble* at pci? dev ? function ? # PCnet-PCI Ethernetpcn* at pci? dev ? function ? # AMD PCnet-PCI Ethernetrtk* at pci? dev ? function ? # Realtek 8129/8139
amhphy* at mii? phy ? # AMD 79c901 Ethernet PHYsurlphy* at mii? phy ? # Realtek RTL8150L internal PHYsukphy* at mii? phy ? # generic unknown PHYs
# Pseudo-Devices
# disk/mass storage pseudo-devicespseudo-device md 1 # memory disk device (ramdisk)#pseudo-device vnd 4 # disk-like interface to files
# network pseudo-devicespseudo-device bpfilter 8 # Berkeley packet filterpseudo-device ipfilter # IP filter (firewall) and NATpseudo-device loop # network loopbackpseudo-device ppp 2 # Point-to-Point Protocolpseudo-device pppoe 3
# miscellaneous pseudo-devicespseudo-device pty 2 # pseudo-terminals (Sysinst needs two)# wscons pseudo-devicespseudo-device wsmux # mouse & keyboard multiplexor#pseudo-device wsfont
2、制作ramdisk镜像# dd if=/dev/zero of=/ramdisk bs=512 count=9000# vnconfig -c /dev/vnd0d /ramdisk# disklabel -r -w /dev/vnd0d rdroot# newfs -m 0 -S 512 -i 4096 /dev/vnd0a# mount /dev/vnd0a /mnt# mkdir /mnt/{dev,bin,sbin,etc}# cp /dev/MAKEDEV /mnt/dev# cp /bin/{sh,ls} /mnt/bin# cp /sbin/init /mnt/sbin# cd /mnt/dev/ && ./MAKEDEV ramdisk# echo 'echo "This is my minibsd all in kernel" && /bin/sh' > /mnt/etc/rc# sync && umount /mnt# sync && vnconfig -u vnd0d && sync
3、将ramdisk写入kernel# mdsetroot /minibsd ramdisk
4、压缩kernel大小# gzip -9 -c /minibsd > /minibsd.gz
5、制作目标软盘
因为系统需要使用/boot（/usr/mdec/boot）来加载kernel，所以我们需要在软盘上放置boot文件。
