已有 rootfs.cramfs
mount -t cramfs -o loop rootfs.cramfs /mnt
制作cramfs
mkfs.cramfs [-h] [-v] [-b blksize] [-e edition] [-N endian] [-i file] [-n name] dirname outfile
-h print this help
-v be verbose
-E make all warnings errors (non-zero exit status)
-b blksize use this blocksize, must equal page size
-e edition set edition number (part of fsid)
-N endian set cramfs endianness (big|little|host), default host
-i file insert a file image into the filesystem (requires >= 2.4.0)
-n name set name of cramfs filesystem
-p pad by 512 bytes for boot code
-s sort directory entries (old option, ignored)
-z make explicit holes (requires >= 2.3.39)
dirname root of the filesystem to be compressed
outfile output file
usage: mkcramfs [-h] [-b blksize] [-e edition] [-i file] [-n name] dirname outfile
-h print this help
-E make all warnings errors (non-zero exit status)
-b blksize blocksize to use
-e edition set edition number (part of fsid)
-i file insert a file image into the filesystem (requires >= 2.4.0)
-n name set name of cramfs filesystem
-p pad by 512 bytes for boot code
-s sort directory entries (old option, ignored)
-v be more verbose
-z make explicit holes (requires >= 2.3.39)
dirname root of the directory tree to be compressed
outfile output file
当bootloader中， 把 kernel / rootfs 从 TF 卡读到 RAM 中后，直接引导内核即可。
"movi read kernel c0008000;movi read rootfs c0800000;bootm c0008000"
内核于rootfs.cramfs 的映射关系可以通过 arch/arm/mach-xxx/Makefile.boot中的initrd_phys-y := 0xc0800000 参数指定，
或者通过引导命令行
【CONFIG_CMDLINE="mem=32M console=ttySA0,38400n8 initrd=0xc0800000,3M root=/dev/ram"】
【
#define CONFIG_BOOTARGS_MOVI "root=/dev/ram0 rw initrd=0x50800000,8M console=ttySAC0,115200"
#define CONFIG_BOOTARGS_NAND "root=/dev/sftl2 rootfstype=cramfs console=ttySAC0,115200"
】
【CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rwroot=/dev/mtdblock2mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root)load_ramdisk=1 prompt_ramdisk=0 mem=32M noinitrd initrd=0xc0800000,3M"】