This shows a basic use for QEMU.

See also QEMU Documentation

QEMU can emulate different processor architectures:

• qemu-system-arm: ARM
• qemu-system-mips: MIPS
• qemu-system-ppc: PowerPC
• qemu-system-x86: x86 and x86_64

QEMU emulates lot of hardware for each architecture which can be shown with the option -machine help.

Example use:

qemu-system-arm -machine vexpress-a9 -m 256M -drive file=rootfs.ext4,sd -net nic -net use -kernel zImage -dtb vexpress-v2p-ca9.dtb -append "console=ttyAMA0,115200 root=/dev/mmcblk0" -serial stdio -net nic,model=lan9118 -net tap,ifname=tap0

The most important options are:

• -machine vexpress-a9: emulation of ARM Versatile Express development board (with Cortex A-9 processor)
• -m 256M: 256 MiB RAM
• -drive file=rootfs.ext4,sd: connect the sd interface to the file rootfs.ext4 (filesystem image)
• -kernel zImage: loads the Linux kernel from the file zImage
• -dtb vexpress-v2p-ca9.dtb: loads the device tree from the file vexpress-v2p-ca9.dtb
• -append "...": supplies this string as the kernel command line
• -serial stdio: connects the serial port to the terminal that launched QEMU, so you can log via the serial console
• -net nic,model=lan9118: creates a network interface
• -net tap,ifname=tap0: connects the network interface to the virtual network interface tap0

For configuring the network interface the command tunctl is used:

sudo tunctl -u $(whoami) -t tap0

This creates a network interface named tap0 which is connected to the network controller in the emulated QEMU machine.

The tunctl command is available from the User Mode Linux (UML) project (uml-utilites).

Loading an image from Ramdisk

Use the option -initrd to load initramfs into memory:

QEMU_AUDIO_DRV=none \
qemu-system-arm -m 256M -nographic -M versatilepb \
-kernel zImage -append "console=ttyAMA0 rdinit=/bin/sh" \
-dtb versatile-pb.dtb -initrd initramfs.cpio.gz