This content originally appeared on DEV Community and was authored by Franz Wong
Background
I would like to share a folder between guest and host in QEMU. File permission should be the same as the user in host.
Solution
1. Create a folder called shared in host
mkdir -p shared
2. Add a parameter virtfs when starting VM with QEMU
-virtfs local,path=shared,mount_tag=shared,security_model=mapped-xattr
3. After the VM is started, login to the VM and create mount point
mkdir -p /mnt/shared
4. Mount the folder
sudo mount -t 9p -o trans=virtio,version=9p2000.L shared /mnt/shared
5. Check the permission of mount point
ls -l -d /mnt/shared
It should be something like the following. On my host machine, my user ID is 501 and primary group ID is 20. (It’s common setting in MacOS). In the guest VM, the group with ID 20 is called dialout. (You can check in /etc/group).
drwxr-xr-x 3 501 dialout 96 Jul 14 03:44 /mnt/shared
However, my user in guest VM has uid 1000 and the primary group id is 1000 too. We need to make a mapping.
id
uid=1000(franz) gid=1000(dev_users) groups=1000(dev_users),27(sudo)
6. Install bindfs in guest VM
sudo apt install -y bindfs
7. Create the mapping
sudo bindfs --map=501/1000:@dialout/@1000 /mnt/shared /mnt/shared
8. Check the permission of mount point again
ls -l -d /mnt/shared
This time the permission is correct.
drwxr-xr-x 3 franz dev_users 96 Jul 14 03:44 /mnt/shared
Reference: 9p/virtfs share not writable
This content originally appeared on DEV Community and was authored by Franz Wong