Some notes on QEMU

I am finding a computer emulator so that I can use to experiment some low-level softwares. There are two prominent free and open-source emulators: Bochs and QEMU. Bochs seems more popular but lacks of documentation. So I have decided to use QEMU because it's quite simple to use and well documented.

1. Installation (on Ubuntu)
    $ sudo apt-get install qemu

2. Start emulator
    $ qemu [options] [disk_image] 
       --> This means start an emulator with specified options and disk_image (usually contains OS)

    Ex:
      $ qemu linux.img
             --> Start an emulator with default options and its hard disk contains linux.img

    There are lots of options which specify how your emulated computer could be such as what type of its cpu, hard disk, video card, sound card,... You can get more details on each option in QEMU documentation.

3. Monitoring
    QEMU provides a way to monitoring your emulator in which you can inspect your emulator, control it, change its devices, query its status,...

    You can switch back and forth between the emulator and its monitor with keystrokes: Ctrl+Alt+2 and Ctrl+Alt+1

    Some monitoring commands:
    (qemu) help or ? [cmd] 
    (qemu) change device setting
    (qemu) x/fmt addr
           Virtual memory dump starting at addr
    (qemu) xp/fmt addr
           Physical memory dump starting at addr 
    ...