我正在尝试使用AT91SAM9261和2.6.30内核设置ramdisk。 我知道你会说为什么我不使用initramfs？我也将使用那一个，截至目前我想检查我是否可以使用ramdisk作为rootfs启动。
我已经在jffs2格式的系统上运行了一个root fs。 我使用下面的教程：
http://www.ibm.com/developerworks/library/l-initrd/
所以我直接在嵌入式目标上创建了ramdisk，大小为4MB。 我用了＃34; dd＆＃34;和＆＃34; mkefs＆＃34;当rootfs是我的jffs2时，如果我将它挂载为循环，那么ramdisk图像工作正常。 我可以浏览mount_point并在里面做东西。 内容是根据＆＃34;手动构建初始RAM磁盘＆＃34;部分创建的。在上面的链接。
在/ dev中我放置了null和console，在/ bin中我复制了busybox并创建了链接。 我也将execute属性设置为init脚本，这在我在这里运行时效果很好（作为循环设备，jffs2作为rootfs）
在我的内核配置中，我启用了ramdisk支持，如下所示：
CONFIG_BLK_DEV_INITRD=y
CONFIG_RD_GZIP=y
CONFIG_BLK_DEV_RAM=y
CONFIG_BLK_DEV_RAM_COUNT=16
CONFIG_BLK_DEV_RAM_SIZE=4096
使用tftp我将ramdisk图像下载到0x21100000。 在0x20008000我没有压缩内核，并且在0x22000000处复制了zImage。
但是，我在检查init进程时挂起时无法成功启动系统。 正如我所提到的，我多次检查过我的init可以执行，
我还在bootargs init = / bin / busybox或其他脚本/二进制文件中使用，以检查是否可以将其用作init。
我现在使用的命令行：
bootargs = 64M console = ttyS0,115200 root = / dev / ram0 rw initrd = 0x21100000,4194304 init = / init
对于某些人，我将所有权设置为＆＃34; nobody＆＃34;只是为了检查它是否有任何区别。 正如在日志输出中可以看到的那样，挂载了ramdisk，但是init失败了。 它给出了一个警告来检查ext2图像，我在复制它之前做了这个，并且没有报告错误。
tftp服务器在Windows7上。如果我将ramdisk图像从linux复制到Windows然后从Windows服务器执行tftp，我可能会有一些不兼容性。 所以我再次将图像从Windows复制到linux，安装它并检查FS是否报告任何错误并且脚本可以执行 - 一切看起来都正常。
所以我确实有所有文件，属性集，ramdisk被报告为以rootfs身份安装好，但是找不到init。
Uncompressing Linux......................................................................................................... done, booting the kernel.
Linux version 2.6.30-olimex (mishu@KubuntuVM) (gcc version 4.3.3 (Sourcery G++ Lite 2009q1-203) ) #1 Mon Dec 29 13:53:54 CET 2014
CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=00053177
CPU: VIVT data cache, VIVT instruction cache
Machine: Olimex SAM9-L9261
Ignoring unrecognised tag 0x54410008
Memory policy: ECC disabled, Data cache writeback
Clocks: CPU 198 MHz, master 99 MHz, main 18.432 MHz
Built 1 zonelists in Zone order, mobility grouping on. Total pages: 16256
Kernel command line: 64M console=ttyS0,115200 root=/dev/ram0 rw initrd=0x21100000,4194304 init=/init
NR_IRQS:192
AT91: 96 gpio irqs in 3 banks
PID hash table entries: 256 (order: 8, 1024 bytes)
Console: colour dummy device 80x30
console [ttyS0] enabled
Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
Memory: 64MB = 64MB total
Memory: 57384KB available (2924K code, 246K data, 132K init, 0K highmem)
Calibrating delay loop... 99.12 BogoMIPS (lpj=495616)
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
net_namespace: 716 bytes
NET: Registered protocol family 16
AT91: Power Management
AT91: Starting after user reset
bio: create slab <bio-0> at 0
SCSI subsystem initialized
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
NET: Registered protocol family 2
IP route cache hash table entries: 1024 (order: 0, 4096 bytes)
TCP established hash table entries: 2048 (order: 2, 16384 bytes)
TCP bind hash table entries: 2048 (order: 1, 8192 bytes)
TCP: Hash tables configured (established 2048 bind 2048)
TCP reno registered
NET: Registered protocol family 1
Trying to unpack rootfs image as initramfs...
rootfs image is not initramfs (junk in compressed archive); looks like an initrd
Freeing initrd memory: 4096K
NetWinder Floating Point Emulator V0.97 (double precision)
JFFS2 version 2.2. (NAND) (SUMMARY) © 2001-2006 Red Hat, Inc.
msgmni has been set to 120
io scheduler noop registered
io scheduler anticipatory registered (default)
atmel_lcdfb atmel_lcdfb.0: backlight control is not available
atmel_lcdfb atmel_lcdfb.0: 225KiB frame buffer at 23140000 (mapped at ffc00000)
Console: switching to colour frame buffer device 40x30
atmel_lcdfb atmel_lcdfb.0: fb0: Atmel LCDC at 0x00600000 (mapped at c4866000), irq 21
atmel_usart.0: ttyS0 at MMIO 0xfefff200 (irq = 1) is a ATMEL_SERIAL
atmel_usart.1: ttyS1 at MMIO 0xfffb0000 (irq = 6) is a ATMEL_SERIAL
brd: module loaded
loop: module loaded
ssc ssc.1: Atmel SSC device at 0xc4878000 (irq 15)
Driver 'sd' needs updating - please use bus_type methods
dm9000 Ethernet Driver, V1.31
eth0 (dm9000): not using net_device_ops yet
eth0: dm9000e at c486a000,c486e044 IRQ 107 MAC: 3a:1f:34:08:54:64 (chip)
NAND device: Manufacturer ID: 0xec, Chip ID: 0xdc (Samsung NAND 512MiB 3,3V 8-bit)
Scanning device for bad blocks
Bad eraseblock 1478 at 0x00000b8c0000
Creating 2 MTD partitions on "atmel_nand":
0x000000000000-0x000000040000 : "Partition 1"
0x000000040000-0x000020000000 : "Partition 2"
atmel_spi atmel_spi.0: Atmel SPI Controller at 0xfffc8000 (irq 12)
ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
at91_ohci at91_ohci: AT91 OHCI
at91_ohci at91_ohci: new USB bus registered, assigned bus number 1
at91_ohci at91_ohci: irq 20, io mem 0x00500000
usb usb1: New USB device found, idVendor=1d6b, idProduct=0001
usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
usb usb1: Product: AT91 OHCI
usb usb1: Manufacturer: Linux 2.6.30-olimex ohci_hcd
usb usb1: SerialNumber: at91
usb usb1: configuration #1 chosen from 1 choice
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
Initializing USB Mass Storage driver...
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
udc: at91_udc version 3 May 2006
g_serial gadget: Gadget Serial v2.4
g_serial gadget: g_serial ready
mice: PS/2 mouse device common for all mice
input: gpio-keys as /class/input/input0
ads7846 spi0.2: touchscreen, irq 29
input: ADS784x Touchscreen as /class/input/input1
rtc-at91sam9 at91_rtt.0: rtc core: registered at91_rtt as rtc0
IRQ 1/rtc0: IRQF_DISABLED is not guaranteed on shared IRQs
rtc-at91sam9 at91_rtt.0: rtc0: SET TIME!
i2c /dev entries driver
i2c-gpio: probe of i2c-gpio failed with error -16
Registered led device: led1
Registered led device: led2
Registered led device: led3
Advanced Linux Sound Architecture Driver Version 1.0.20.
at73c213 spi0.3: at73c213: supported bitrate is 48500 (64 divider)
usb 1-1: new full speed USB device using at91_ohci and address 2
usb 1-1: New USB device found, idVendor=0457, idProduct=0151
usb 1-1: New USB device strings: Mfr=0, Product=2, SerialNumber=3
usb 1-1: Product: USB Mass Storage Device
usb 1-1: SerialNumber: 8d54bd8186b42c
usb 1-1: configuration #1 chosen from 1 choice
scsi0 : SCSI emulation for USB Mass Storage devices
ALSA device list:
#0: SAM9-L9261 external DAC on irq 15
TCP cubic registered
NET: Registered protocol family 17
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
rtc-at91sam9 at91_rtt.0: hctosys: unable to read the hardware clock
RAMDISK: ext2 filesystem found at block 0
RAMDISK: Loading 4096KiB [1 disk] into ram disk... done.
EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended
VFS: Mounted root (ext2 filesystem) on device 1:0.
Freeing init memory: 132K
Failed to execute /init. Attempting defaults...
Kernel panic - not syncing: No init found. Try passing init= option to kernel.
[<c002f414>] (unwind_backtrace+0x0/0xdc) from [<c025bd34>] (panic+0x40/0x110)
[<c025bd34>] (panic+0x40/0x110) from [<c0029500>] (init_post+0xd0/0xf8)
[<c0029500>] (init_post+0xd0/0xf8) from [<c00085a0>] (kernel_init+0xbc/0xe4)
[<c00085a0>] (kernel_init+0xbc/0xe4) from [<c0041998>] (do_exit+0x0/0x5ac)
[<c0041998>] (do_exit+0x0/0x5ac) from [<00000001>] (0x1)
我计划重建busybox并重试，但是当我将当前的ramdisk图像作为循环安装时，我不会有太多的信心它会改变一些东西。 我没有想法。我一整天都在尝试让这个工作。
非常感谢帮助。
感谢。
答案 0 :(得分：1)
缺少库是ramdisk上放置的非可执行 init 的根本原因。
使用chroot证明非常有用。通过这个问题，我学会了如何使用chroot并模拟监狱。
另一个技巧是在命令行中使用user_debug=31，以便内核输出一条消息，说明找不到该文件。
看起来“找不到文件”并没有真正指向丢失文件，而是由于 busybox 未正确执行而导致文件系统无法读取（缺少库）。
同时我已经动态编译了busybox 1.20.02 for arm arm架构并且ramdisk正常工作（没有libs）。
这个user_debug=31在我编译并运行busybox时再次变得有用，因为它在安装ramdisk之后也失败了，但它抛出了一个“未定义的异常”，这导致我使用了一个错误的“arch”值编译busybox。改变后一切都很好。