What?

A simple command line wrapper for Qemu on macOS.

Features

Defaults to native Qemu platform
- Works on both x86_64 and arm64 macOS
Attaches drives with TRIM/discard enabled for fstrim
- Note that qcow drive images are sparse - logical size will not shrink
Uses socket_vmnet for networking if installed
Generates a unique ethernet MAC from provided disk image path(s)
Defaults to serial console on stdio with no graphics - works with:
- Debian-nocloud
- Alpine-virt
Bundles aarch64 QEMU_EFI.fd, as Homebrew Qemu does not
Remaps VM monitor escape sequence from ctrl-a to ctrl-g
- ^{_{Because I cannot remap my fingers}}

Dependencies

Qemu - installable via Homebrew:
- brew install qemu
socket_vmnet (optional)
- lets virtual machines configure a virtual network interface without having to run the entire Qemu process as root*
- gives your VM(s) a real local IP address, making it easy to host network services

* As of Qemu 7.1, either this:

-nic vmnet-bridged,mac=00:11:22:33:44:55,ifname=en0

or this:

-device virtio-net-pci,netdev=vmnet0,mac=00:11:22:33:44:55
-netdev vmnet-bridged,id=vmnet0,ifname=en0

will work, but only via sudo, as the com.apple.vm.networking entitlement is currently restricted.

Install

make install

builds/installs to /usr/local/bin/vm

Run

Run with no arguments for help, but in brief, supply it one or more qcow2 or ISO images:

vm disk.qcow2

Miscellaneous

Commands

Within a VM, shut it down gracefully by running:

poweroff (for Debian or Alpine)

Manually release blocks backing deleted files in your VM:

fstrim -va (or fstrim / on Alpine)

Clock shenanigans

On x86_64 linux you may get a lot of complaints about the clock on the console:

[   31.538691] clocksource: wd-tsc-wd read-back delay of 133000ns, clock-skew test skipped!
[   32.014140] clocksource: timekeeping watchdog on CPU0: hpet wd-wd read-back delay of 58000ns
[   32.020628] clocksource: wd-tsc-wd read-back delay of 156000ns, clock-skew test skipped!
[   34.030150] clocksource: timekeeping watchdog on CPU0: hpet wd-wd read-back delay of 58000ns
[   34.036468] clocksource: wd-tsc-wd read-back delay of 154000ns, clock-skew test skipped!
[   34.510992] clocksource: timekeeping watchdog on CPU0: hpet wd-wd read-back delay of 58000ns
[   34.517297] clocksource: wd-tsc-wd read-back delay of 158000ns, clock-skew test skipped!
[   36.526046] clocksource: timekeeping watchdog on CPU0: hpet wd-wd read-back delay of 54000ns
[   36.532508] clocksource: wd-tsc-wd read-back delay of 132000ns, clock-skew test skipped!

To remedy, try this:

sed -i '/^GRUB_CMDLINE_LINUX=/s/"$/ tsc=unstable"/' /etc/default/grub
update-grub
reboot

Serial console

This works great for automatically configuring serial console dimensions.

For Alpine, try:

apk add gcc curl musl-dev ncurses-dev
curl -LO https://raw.githubusercontent.com/lime45/serial/master/resize.c
sed -i 's/termio.h/sys\/ioctl.h/' resize.c
gcc -s -Os resize.c -o /usr/local/bin/resize

Or for Debian try:

apt update && apt install gcc curl ncurses-dev
curl -LO https://raw.githubusercontent.com/lime45/serial/master/resize.c
gcc -s -Os resize.c -o /usr/local/bin/resize

Run it anytime your terminal dimensions change.

To have it run once on serial console login, try:

cat << "EOF" > /etc/profile.d/resize.sh
#!/bin/sh
tty=`tty`
if [ "${tty::9}" = "/dev/ttyS" ]; then
	/usr/local/bin/resize
fi
EOF

Thanks

I ran across the macbian-linux macos-subsystem-for-linux project on HN - it was super helpful and motivated me to give qemu on macOS a serious try.

lima-vm's socket_vmnet project

lime45's serial project

nwpierce/qvm