Booting from an ISO image using qemu


Qemu has two operating mode named full system emulation and user mode emulation. If you want to simulate whole system not just the cpu (like a PC) you need to use full system emulation mode.

Newer distributions have separate binaries for these two different operation modes. For example, if you just want user mode cpu emulation for X86-64 architecture, you need to use qemu-x86_64 binary and if you need whole X86-64 bit system emulation (like your PC), qemu-system-x86_64 binary must be used in commands below.

You have an iso image and you want to boot from it without restarting the system, simply use qemu virtual machine as below (-m 512 says qemu will be use 512 Mb of RAM from system):

qemu-system-x86_64 -boot d -cdrom image.iso -m 512

It is also possible to use your regular cdrom device too. If the device is /dev/cdrom you can boot a cd in the device like that:

qemu-system-x86_64 -boot d -cdrom /dev/cdrom -m 512

Above examples not use any harddisk, so it is suitable for live cd image case. If you want to install a distribution to a harddisk image file, you need to create harddisk image file first:

qemu-img create mydisk.img 10G

In this example we’re created an image of 10 GB. Now we can use this file as harddisk in our qemu boot:

qemu-system-x86_64 -boot d -cdrom image.iso -m 512 -hda mydisk.img


Hi, i have issue when create VM with qemu-system-x86_64?
When i create VM by qemu-system-x86_64 with
file iso(2Gb)
ram 2048,
score 2,
then the install progress take long times (about 4hours)? i don’t know why it install VM very slow? I wan’t to check log install progress and solve issue that?

Please help me.


If you give the -enable-kvm parameter but the emulation still so slow, probably Intel VT-x or AMD AMD-V CPU Virtualization Technology support is disabled by the BIOS.

Can you check Virtualization Support settings in BIOS? If your system doesn’t provide one of these technologies, everything will be emulated by the software.