一直想解决在嵌入式linux运行的时候，动态更新cramfs，今天用mtd_debug实现了对kernel和rootfs的运行时更新。 同时还使用了dd以及nandwrite,发现dd对一个文件是可以的，但是写入另一文件后，内核启动的过程中出现了ECC的kernel panic。 而使用nandwrite则一次都不能成功。 --=================================================-- 1. OK /root/mtd_utils # ./mtd_debug write /dev/mtdblock/1 0x0 1218604 zImage Copied 1218604 bytes from zImage to address 0x00000000 in flash ./mtd_debug write /dev/mtdblock/2 0x0 2404352 ./rootfs.my.cramfs # ok ./mtd_debug write /dev/mtdblock/2 0x0  2416640 rootfs080626.cramfs # ok ./mtd_debug write /dev/mtd/2 0x0  2416640 rootfs080626.cramfs # write ok, run ok! 注意mtd_debug的长度参数，要<=文件的长度，才会写入到mtd中,否则会给出如下提示并退出: file_to_flash: fread, size 0x1297f5, n 0x1297f5 fread(): Success --=================================================-- 2. 参数错误 /root/mtd_utils # ./mtd_debug write /dev/mtd/1 0x0 1218604 zImage MTD_open MTD_write nand_write_ecc: Attempt to write not page aligned data fileMTD_close _to_flash: write, size 0x12982c, n 0x12982c write(): Invalid argument --=================================================-- 3. dd 有的时候可以，有的时候不能运行,可能跟cramfs的内容有关系 dd if=rootfs.my.cramfs of=/dev/mtdblock/2 # OK dd if=rootfs.my.cramfs of=/dev/mtd/2 (writing '/dev/mtd/2': Invalid argument) dd if=rootfs080626.cramfs of=/dev/mtdblock/2 # ecc error --=================================================-- 4. nandwrite 不行 ./nandwrite /dev/mtd/2 ./rootfs.my.cramfs # Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0) ./nandwrite /dev/mtd/2  ./rootfs080626.cramfs # failed, can not mount ./nandwrite /dev/mtdblock/2 ./rootfs080626.cramfs # MEMGETINFO: Inappropriate ioctl for device