uboot源代碼的tools/目錄下有mkimage工具，這個工具可以用來制作不壓縮或者壓縮的多種可啟動映象檔案。
mkimage在制作映象檔案的時候，是在原來的可執行映象檔案的前面加上一個0x40位元組的頭，記錄參數所指定的資訊，這樣uboot才能識别這個映象是針對哪個CPU體系結構的，哪個OS的，哪種類型，加載記憶體中的哪個位置， 入口點在記憶體的那個位置以及映象名是什麼
root@Glym:/tftpboot# ./mkimage
Usage: ./mkimage -l image
-l ==> list image header information
./mkimage -A arch -O os -T type -C comp -a addr -e ep -n name -d data_file[:data_file...] image
-A ==> set architecture to 'arch'
-O ==> set operating system to 'os'
-T ==> set image type to 'type'
-C ==> set compression type 'comp'
-a ==> set load address to 'addr' (hex)
-e ==> set entry point to 'ep' (hex)
-n ==> set image name to 'name'
-d ==> use image data from 'datafile'
-x ==> set XIP (execute in place)
參數說明：
-A 指定CPU的體系結構：
取值 表示的體系結構
alpha Alpha
arm A RM
x86 Intel x86
ia64 IA64
mips MIPS
mips64 MIPS 64 Bit
ppc PowerPC
s390 IBM S390
sh SuperH
sparc SPARC
sparc64 SPARC 64 Bit
m68k MC68000
-O 指定作業系統類型，可以取以下值：
openbsd、netbsd、freebsd、4_4bsd、linux、svr4、esix、solaris、irix、sco、dell、ncr、lynxos、vxworks、psos、qnx、u-boot、rtems、artos
-T 指定映象類型，可以取以下值：
standalone、kernel、ramdisk、multi、firmware、script、filesystem
-C 指定映象壓縮方式，可以取以下值：
none 不壓縮
gzip 用gzip的壓縮方式
bzip2 用bzip2的壓縮方式
-a 指定映象在記憶體中的加載位址，映象下載下傳到記憶體中時，要按照用mkimage制作映象時，這個參數所指定的位址值來下載下傳
-e 指定映象運作的入口點位址，這個位址就是-a參數指定的值加上0x40（因為前面有個mkimage添加的0x40個位元組的頭）
-n 指定映象名
-d 指定制作映象的源檔案
<a href="http://www.cnitblog.com/luofuchong/archive/2007/01/12/21834.html">U-BOOT下使用bootm引導核心方法</a>
一、在開始之前先說明一下bootm相關的東西。
1、 首先說明一下，S3C2410架構下的bootm隻對sdram中的核心鏡像檔案進行操作(好像AT91架構提供了一段從flash複制核心鏡像的代碼， 不過針對s3c2410架構就沒有這段代碼，雖然可以在u-boot下添加這段代碼，不過好像這個用處不大)，是以請確定你的核心鏡像下載下傳到sdram 中，或者在bootcmd下把flash中的核心鏡像複制到sdram中。
2、-a參數後是核心的運作位址，-e參數後是入口位址。
3、
1）如果我們沒用mkimage對核心進行處理的話，那直接把核心下載下傳到0x30008000再運作就行，核心會自解壓運作（不過核心運作需要一個tag來傳遞參數，而這個tag建議是由bootloader提供的，在u-boot下預設是由bootm指令建立的）。
2）如果使用mkimage生成核心鏡像檔案的話，會在核心的前頭加上了64byte的資訊，供建立tag之用。bootm指令會首先判斷bootm xxxx 這個指定的位址xxxx是否與-a指定的加載位址相同。
(1)如果不同的話會從這個位址開始提取出這個64byte的頭部，對其進行分析，然後把去掉頭部的核心複制到-a指定的load位址中去運作之
(2)如果相同的話那就讓其原封不同的放在那，但-e指定的入口位址會推後64byte，以跳過這64byte的頭部。
二、好，接着介紹使用mkimage生成鏡像檔案并下載下傳運作的方法。
方法一、
1、首先，用u-boot/tools/mkimage這個工具為你的核心加上u-boot引導所需要的檔案頭，具體做法如下：
[root@localhost tftpboot]#mkimage -n 'linux-2.6.14' -A arm -O linux -T kernel -C none -a 0x30008000 -e 0x30008000 -d zImage zImage.img
Image Name: linux-2.6.14
Created: Fri Jan 12 17:14:50 2007
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 1262504 Bytes = 1232.91 kB = 1.20 MB
Load Address: 0x30008000
Entry Point: 0x30008000
這裡解釋一下參數的意義：
-A ==> set architecture to 'arch'
-O ==> set operating system to 'os'
-T ==> set image type to 'type'
-C ==> set compression type 'comp'
-a ==> set load address to 'addr' (hex)
-e ==> set entry point to 'ep' (hex)
-n ==> set image name to 'name'
-d ==> use image data from 'datafile'
-x ==> set XIP (execute in place)
2 、下載下傳核心
U-Boot 1.1.3 (Jan 12 2007 - 16:16:36)
U-Boot code: 33F80000 -> 33F9BAC0 BSS: -> 33F9FBAC
RAM Configuration:
Bank #0: 30000000 64 MB
Nor Flash: 512 kB
Nand Flash: 64 MB
In: serial
Out: serial
Err: serial
Hit any key to stop autoboot: 0
sbc2410=>tftp 0x31000000 zImage.img
TFTP from server 192.168.1.115; our IP address is 192.168.1.128
Filename 'zImage.img'.
Load address: 0x31000000
Loading: #################################################################
#################################################################
####################################################
done
Bytes transferred = 1263324 (1346dc hex)
3.運作
sbc2410=>bootm 0x31000000
## Booting image at 31000000 ...
Image Name: linun-2.6.14
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 1263260 Bytes = 1.2 MB
Load Address: 30008000
Entry Point: 30008000
Verifying Checksum ... OK
OK
Starting kernel ...
Uncompressing Linux.............................................................Linux version 2.6.14 (root@luofuchong) (gcc version 3.4.1) #21 Fri Oct 20 17:206CPU: ARM920Tid(wb) [41129200] revision 0 (ARMv4T)
Machine: SMDK2410
Memory policy: ECC disabled, Data cache writeback
CPU S3C2410A (id 0x32410002)
S3C2410: core 202.800 MHz, memory 101.400 MHz, peripheral 50.700 MHz
S3C2410 Clocks, (c) 2004 Simtec Electronics
CLOCK: Slow mode (1.500 MHz), fast, MPLL on, UPLL on
USB Control, (c) 2006 sbc2410
CPU0: D VIVT write-back cache
CPU0: I cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets
CPU0: D cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets
Built 1 zonelists
Kernel command line: console="ttySAC0" root="/dev/nfs" nfsroot="192".168.1.115:/frien"irq: clearing subpending status 00000002
PID hash table entries: 512 (order: 9, 8192 bytes)
timer tcon="00500000", tcnt a509, tcfg 00000200,00000000, usec 00001e4c
Console: colour dummy device 80x30
Dentry cache hash table entries: 16384 (order: 4, 65536 bytes)
Inode-cache hash table entries: 8192 (order: 3, 32768 bytes)
Memory: 64MB = 64MB total
Memory: 62208KB available (1924K code, 529K data, 108K init)
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
softlockup thread 0 started up.
NET: Registered protocol family 16
S3C2410: Initialising architecture
SCSI subsystem initialized
usbcore: registered new driver usbfs
usbcore: registered new driver hub
S3C2410 DMA Driver, (c) 2003-2004 Simtec Electronics
DMA channel 0 at c4800000, irq 33
DMA channel 1 at c4800040, irq 34
DMA channel 2 at c4800080, irq 35
DMA channel 3 at c48000c0, irq 36
NetWinder Floating Point Emulator V0.97 (double precision)
devfs: devfs_debug: 0x0
devfs: boot_options: 0x1
yaffs Oct 18 2006 12:39:51 Installing.
Console: switching to colour frame buffer device 30x40
fb0: s3c2410fb frame buffer device
fb1: Virtual frame buffer device, using 1024K of video memory
led driver initialized
s3c2410 buttons successfully loaded
s3c2410_serial0 at MMIO 0x50000000 (irq = 70) is a S3C2410
s3c2410_serial1 at MMIO 0x50004000 (irq = 73) is a S3C2410
s3c2410_serial2 at MMIO 0x50008000 (irq = 76) is a S3C2410
io scheduler noop registered
io scheduler anticipatory registered
io scheduler deadline registered
io scheduler cfq registered
RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize
usbcore: registered new driver ub
Cirrus Logic CS8900A driver for Linux (Modified for SMDK2410)
eth0: CS8900A rev E at 0xe0000300 irq="53", no eeprom , addr: 08: 0:3E:26:0A:5B
S3C24XX NAND Driver, (c) 2004 Simtec Electronics
s3c2410-nand: mapped registers at c4980000
s3c2410-nand: timing: Tacls 10ns, Twrph0 30ns, Twrph1 10ns
NAND device: Manufacturer ID: 0xec, Chip ID: 0x76 (Samsung NAND 64MiB 3,3V 8-bi)Scanning device for bad blocks
Bad eraseblock 1884 at 0x01d70000
Creating 4 MTD partitions on "NAND 64MiB 3,3V 8-bit":
0x00000000-0x00020000 : "vivi"
0x00020000-0x00030000 : "param"
0x00030000-0x00200000 : "kernel"
0x00200000-0x04000000 : "root"
usbmon: debugfs is not available
s3c2410-ohci s3c2410-ohci: S3C24XX OHCI
s3c2410-ohci s3c2410-ohci: new USB bus registered, assigned bus number 1
s3c2410-ohci s3c2410-ohci: irq 42, io mem 0x49000000
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
Initializing USB Mass Storage driver...
usbcore: registered new driver usb-storage
USB Mass Storage support registered.
usbcore: registered new driver usbmouse
drivers/usb/input/usbmouse.c: v1.6:USB HID Boot Protocol mouse driver
mice: PS/2 mouse device common for all mice
s3c2410 TouchScreen successfully loaded
UDA1341 audio driver initialized
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0, 4096 bytes)
TCP established hash table entries: 4096 (order: 2, 16384 bytes)
TCP bind hash table entries: 4096 (order: 2, 16384 bytes)
TCP: Hash tables configured (established 4096 bind 4096)
TCP reno registered
TCP bic registered
NET: Registered protocol family 1
IP-Config: Complete:
device=eth0, addr="192".168.1.128, mask="255".255.255.0, gw="192".168.1.1,
host="luofuchong", domain=, nis-domain=(none),
bootserver="192".168.1.1, rootserver="192".168.1.115, rootpath=
Looking up port of RPC 100003/2 on 192.168.1.115
Looking up port of RPC 100005/1 on 192.168.1.115
VFS: Mounted root (nfs filesystem).
Mounted devfs on /dev
Freeing init memory: 108K
init started: BusyBox v1.1.3 (2006.09.20-14:52+0000) multi-call binary
Starting pid 696, console /dev/tts/0: '/etc/init.d/rcS'
Please press Enter to activate this console.
方法二、
[root@localhost tftpboot]#mkimage -n 'linux-2.6.14' -A arm -O linux -T kernel -C none -a 0x30008000 -e 0x30008040 -d zImage zImage.img
Entry Point: 0x30008040
sbc2410=>tftp 0x30008000 zImage.img
Load address: 0x30008000
sbc2410=>bootm 0x30008000
## Booting image at 30008000 ...
Image Name: linux-2.6.14
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 1261056 Bytes = 1.2 MB
Load Address: 30008000
Entry Point: 30008040
Verifying Checksum ... OK
XIP Kernel Image ... OK
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