将镜像文件作为交换分区

创建镜像文件：

dd if=/dev/zero of=swap.img bs=512 count=131072

qemu-system-arm -nographic -M vexpress-a9 -m 64M -kernel arch/arm/boot/zImage -append "rdinit=/linuxrc console=ttyAMA0 loglevel=8" -dtb arch/arm/boot/dts/vexpress-v2p-ca9.dtb -sd swap.img

~ # mkswap /dev/mmcblk0
Setting up swapspace version 1, size = 67104768 bytes
[   62.306076] random: mkswap urandom read with 112 bits of entropy available
UUID=f1837026-d957-4153-97ab-31f549ec0534
~ # [   72.694766] random: nonblocking pool is initialized
swapon /dev/mmcblk0
[   83.105627] Adding 65532k swap on /dev/mmcblk0.  Priority:-1 extents:1 across:65532k SS
~ # df -h
Filesystem                Size      Used Available Use% Mounted on
tmpfs                    24.8M         0     24.8M   0% /tmp
tmpfs                    24.8M         0     24.8M   0% /dev
~ # free
              total        used        free      shared  buff/cache   available
Mem:          50840       11948       32708        2152        6184       34028
Swap:         65532           0       65532

将镜像文件作为外挂磁盘

dd if=/dev/zero of=ext4.img bs=512 count=131072

格式化：

mkfs.ext4 ext4.img

挂载 ext4 文件系统需要打开如下配置的选项。

[arch/arm/configs/vexpress _ defconfig]

CONFIG _ LBDAF=y

CONFIG_EXT4 _ FS=y

重新编译内核

qemu-system-arm -nographic -M vexpress-a9 -m 64M -kernel arch/arm/boot/zImage -append "rdinit=/linuxrc console=ttyAMA0 loglevel=8" -dtb arch/arm/boot/dts/vexpress-v2p-ca9.dtb -sd ext4.img

系统启动后，手动挂载。

挂载成功。

未验证

在启动命令后使用-sd swap.img报错

WARNING: Image format was not specified for 'swap.img' and probing guessed raw.
Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
Specify the 'raw' format explicitly to remove the restrictions.
qemu-system-aarch64: -sd swap.img: machine type does not support if=sd,bus=0,unit=0

解决办法：将-sd swap.img替换为下面的形式
-drive format=raw,file=swap.img