qemu and host share disk

Sometimes it is necessary to share files between the host and the qemu virtual machine, adding a shared disk will help with this.

Create a 64MB disk image file and format it as ext4 as a spare for shared disk.

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

Modify the qemu startup command and use -hdb to add a disk.

qemu-system-x86_64 -kernel ~/linux-4.14.191/arch/x86_64/boot/bzImage -hda ~/busybox-1.32.0/rootfs.img -append "root=/dev/sda console=ttyS0" -s -smp 1 -nographic -hdb ~/shadisk/ext4.img

After entering the qemu system, use the mount command to mount the sdb to the mnt directory.

Mount ext4.img in the original system to realize file sharing between qemu and the original system.

~/shadisk$ sudo mount -t ext4 -o loop ext4.img ./share