请教如何把rootfs从挂载在flash上改成挂载到ram上？
大侠好，我目前用的是Qualcomm的MSM9x15平台，目前代码中使用的bootcmd为：
KERNEL_BOOT_OPTIONS ?= "root=/dev/mtdblock2 rw rootfstype=yaffs2 rootflags=tags-ecc-off console=ttyHSL0,115200 console=ttyHSL1,115200"
root是挂载在flash上的。
现在的需求要改成挂载到ram上，按照baidu的方法，我试着改了一下：
KERNEL_BOOT_OPTIONS ?= "root=/dev/ram0 rw console=ttyHSL0,115200 console=ttyHSL1,115200"
但是内核启动的时候报错说找不到rootfs，如下面的错误。
对这一块很陌生，请教如何改到挂载到ram上呢？
万谢！List of all partitions:
1f00 1024 mtdblock0(driver?)
1f01 20736 mtdblock1(driver?)
1f02 50688 mtdblock2(driver?)
1f03 40704 mtdblock3(driver?)
1f04 152576 mtdblock4(driver?)
1f05 5376 mtdblock5(driver?)
1f06 2304 mtdblock6(driver?)
No filesystem could mount root, tried:ext3 ext2 ext4 squashfs vfat btrfs yaffs yaffs2
VFS: Unable to mount root fs on unknown-block(1,0)
User configuration error - no valid root filesystem found
Kernel panic - not syncing: Invalid configuration from end user prevents continuing
[<c0014a44>] (unwind_backtrace+0x0/0xfc) from [<c0666ad4>] (dump_stack+0x20/0x24)
[<c0666ad4>] (dump_stack+0x20/0x24) from [<c06670dc>] (panic+0x94/0x1cc)
[<c06670dc>] (panic+0x94/0x1cc) from [<c08fae70>] (mount_block_root+0x1ec/0x238)
[<c08fae70>] (mount_block_root+0x1ec/0x238) from [<c08fb09c>] (mount_root+0xf8/0x11c)
[<c08fb09c>] (mount_root+0xf8/0x11c) from [<c08fb228>] (prepare_namespace+0x168/0x1c8)
[<c08fb228>] (prepare_namespace+0x168/0x1c8) from [<c08faa54>] (kernel_init+0x1ec/0x230)
[<c08faa54>] (kernel_init+0x1ec/0x230) from [<c000ee30>] (kernel_thread_exit+0x0/0x8)
Watchdog bite received from modem software!
modem subsystem failure reason: err.c:537:Error detected on remote processor..
subsys-restart: subsystem_restart(): Restart sequence requested for modem, restart_level = 1.
Kernel panic - not syncing: subsys-restart: Resetting the SoC - modem crashed.
[<c0014a44>] (unwind_backtrace+0x0/0xfc) from [<c0666ad4>] (dump_stack+0x20/0x24)
[<c0666ad4>] (dump_stack+0x20/0x24) from [<c06670dc>] (panic+0x94/0x1cc)
[<c06670dc>] (panic+0x94/0x1cc) from [<c0043e70>] (subsystem_restart+0x1e8/0x234)
[<c0043e70>] (subsystem_restart+0x1e8/0x234) from [<c0044484>] (restart_modem+0xb4/0xd0)
[<c0044484>] (restart_modem+0xb4/0xd0) from [<c0044734>] (modem_wdog_bite_irq+0x38/0x60)
[<c0044734>] (modem_wdog_bite_irq+0x38/0x60) from [<c00b1c94>] (handle_irq_event_percpu+0x98/0x2a4)
[<c00b1c94>] (handle_irq_event_percpu+0x98/0x2a4) from [<c00b1f04>] (handle_irq_event+0x64/0x84)
[<c00b1f04>] (handle_irq_event+0x64/0x84) from [<c00b4a3c>] (handle_fasteoi_irq+0xbc/0x120)
[<c00b4a3c>] (handle_fasteoi_irq+0xbc/0x120) from [<c00b1590>] (generic_handle_irq+0x30/0x40)
[<c00b1590>] (generic_handle_irq+0x30/0x40) from [<c000ed4c>] (handle_IRQ+0x70/0x94)
[<c000ed4c>] (handle_IRQ+0x70/0x94) from [<c00084b4>] (gic_handle_irq+0x48/0x60)
[<c00084b4>] (gic_handle_irq+0x48/0x60) from [<c0671300>] (__irq_svc+0x40/0x70)
Exception stack(0xcf02de48 to 0xcf02de90)
de40: 0001f03a ffffffff 000006fc c0055848 00000000 0000012c
de60: 00000190 0000000a c0a31068 ceab515d c0925c68 cf02debc cf02de90 cf02de90
de80: c06671e8 c03521b0 20000013 ffffffff
[<c0671300>] (__irq_svc+0x40/0x70) from [<c03521b0>] (__delay+0x0/0xc) 本帖最后由 arm-linux-gcc 于 2014-11-05 15:04 编辑
回复 6# fire_vr
设置CONFIG_INITRAMFS_SOURCE路径不要使用打包好之后的，而是要使用源文件路径
不需要制作ram0 image，也不要在cmdline中设置"root="，另外cmdline中需要添加"rdinit=/sbin/init" 先自己顶一下 你的rootfs image有多大？ 有大概36M。。。
[ 本帖最后由 arm-linux-gcc 于 2014-10-30 10:48 编辑 ]
我记得initramfs的size是有限制的，具体多少记不得了，36M的size应该是超了，如果不行就再裁剪一下（只保留必要的，把不必要的放到flash里去）
make menuconfig，配置如下
General setup
[*] Initial RAM filesystem and RAM disk (initramfs/initrd) support
() Initramfs source file(s) 填入你的rootfs源文件的目录地址
Device Drivers
[*] Block devices--->
< > RAM block device support 去掉这个选项
cmdline设置
"console=ttyHSL0,115200 console=ttyHSL1,115200 rdinit=/sbin/init"
本帖最后由 fire_vr 于 2014-11-03 14:22 编辑
谢谢！
我现在裁剪到2M左右了，现在的文件系统打包到Kernel里面，即改CONFIG_INITRAMFS_SOURCE：
CONFIG_INITRAMFS_SOURCE="/devdata/ykong/Rootfs/_install"
但跑起来的时候有下面错误：
我的ram0是在ubuntu上这样生成的，请问有问题吗？
sudo mknod ram0 b 1 0
error：
#0: mdm9615-sitar-snd-ca鶹FS: Cannot open root device "ram0" or unknown-block(1,0): error -2
Please append a correct "root=" boot option; here are the available partitions:
1f00 1024 mtdblock0(driver?)
1f01 20736 mtdblock1(driver?)
1f02 50688 mtdblock2(driver?)
1f03 40704 mtdblock3(driver?)
1f04 152576 mtdblock4(driver?)
1f05 5376 mtdblock5(driver?)
1f06 2304 mtdblock6(driver?)
VFS: Unable to mount root fs on unknown-block(1,0)
User configuration error - no valid root filesystem found 自己顶。。。
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