macOS: mount any linux-supported filesystem read/write using NFS and a microVM
brew tap nohajc/anylinuxfs
brew install anylinuxfs
anylinuxfs-demo.mov
Mounting 3rd-party filesystems on macOS has always been tricky. There's official support for reading NTFS but otherwise we've mainly used solutions based on macFUSE. We've got NTFS-3g which is a pretty mature driver but for Linux filesystems there's only a couple of experimental solutions like fuse-ext2 or ext4fuse.
If you want a reliable solution with write access, you need to run a Linux virtual machine with physical disk access and take care of exposing the mounted filesystem to the host.
This is exactly what anylinuxfs does and it streamlines it so that it's as easy as running one command in terminal.
You pick a drive, mount it with anylinuxfs and it appears as a NFS share on localhost. This spins up a microVM in the background which uses the real linux drivers, so you can access anything from ext* to btrfs. Any mount options on the command-line will be forwarded to the linux mount command, so you can mount read-only, read-write, pick btrfs subvolumes, etc. Then you simply eject the drive in Finder or use umount in terminal and the virtual machine will be turned off.
This all sounds like a lot of work but it's actually very fast. Not like a traditional virtual machine which takes a while to boot. This one is just a stripped down version of Linux, there's not even a UEFI firmware. Practically, it takes only a couple of seconds before the drive is mounted and ready to use.
- When you first run
anylinuxfsto mount a drive, it will download the alpine Linux image from Docker hub and unpack it to your user profile (~/.anylinuxfs/alpine). Then it will spin up a VM so it can install dependencies and do the initial environment setup. After that, the Linux root filesystem will be reused for every mount operation. You can also runanylinuxfs initto download a fresh copy ofalpine:latestand reinitialize the environment at any time. - It is needed to run mount commands with
sudootherwise we're not allowed direct access to/dev/disk*files. However, the virtual machine itself will in fact run under the regular user who invokedsudoin the first place (i.e. all unnecessary permissions are dropped after the disk is opened)
- Only one drive can be mounted at a time (this might be improved in the future)
- Only Apple Silicon Macs are supported (libkrun limitation)
- Check your mount flags (e.g. the
subvolflag from demo is specific to btrfs, make sure you don't use it with other filesystems) - Check file owner and permissions with
ls -land adjust accordingly. Typically, your macOS user won't have write access to your drive out of the box so you need to write files as root or first prepare a target directory writable by everyone (chmod 777). - If you get
fcopyfile failed: Operation not permitted, it can actually mean the file you're trying to copy has the quarantine attribute set (can be removed withxattr -d com.apple.quarantine <filename>) - Accessing disks might require Full Disk Access permission (although you should get pop-ups that let you allow access case-by-case)
This project was made possible by
- libkrun the microVM hypervisor for Linux anc Mac
- libkrunfw - Linux kernel bundled for libkrun as a dynamic library
- gvproxy - user space networking for virtual machines (also used by podman)
- docker-nfs-server - launcher for NFS server in a container
Thank you all for your great work!