How to get 64-bits qemu running in Knoppix 7.X?

I think I might have been able to find out about this myself, but it takes some time and effort, so I ask here: What steps are needed to get 64-bits qemu running in Knoppix 7.X? In principle it should be possible, but my simplistic attempts have so far been futile.

64-bits kernel and the basic 64-bits libraries are already installed, so I can compile 64-bits programs.
What more?

I think this may be useful for many: Running (for example) 64-bits Ubuntu in a VM will let us work with 64-bits builds etc while still staying for the most part in the smoother 32-bits world. Running 64-bits Windows (for example, the version installed on my hard drive). Running 64-bits Oracle XE 11g (there is no 32-bits version for Linux), developing and testing 64-bits OS versions (like Knoppix :) ), cross-compiling, etc etc.

The safest, but maybe not simplest, way, is to setup a 64-bit chroot environment, and install qemu there. Using debootstrap in a pure 64-bits Debian instance, a 64-bits basic system can be installed in some directory, qemu etc installed there and we can chroot into it. This is a very different use scenario from chrooting into a 64-bits install for maintenance/repair, but I think it may be a good way to proceed. One potential problem is that the chroot environment may be setup for another kernel, but when versions are similar, it could work well enough. Ubuntu 12.04 may be a better alternative than Debian 6.0.5 in this respect. Even if it in principle should only depend on .deb versions and not kernel, I don't feel confident it's always that easy.

But I would be very happy to have a simpler alternative to the chroot!

The chroot technique can not only be part of a virtualization procedure, but also an alternative to it.

An example is provided by the Tizen SDK https://source.tizen.org - which I was not able to start installing properly under Knoppix 7.0.3. It says Ubuntu is required, and a relatively close relative does not seem to suffice. Setting up a 32-bit Ubuntu chroot, like detailed by
Tomi Ollila https://www.nixuopen.org/blog/2012/5...bit-fedora-16/ is a way to avoid having too many installs, and run things ass efficiently as possible. (Lots of users run Ubuntu in a VM for such purposes, but that makes SDK things like emulators run rather slowly.)

Basically, we setup a new "install" with debootstrap, chroot into it and install what is needed within that context. I think a 64-bits Ubuntu chroot can be used efficiently for Android development, with (or maybe even without?) the standard SDK (Google uses Ubuntu inhouse), while for Tizen SDK, 32-bits is needed.

So, in addition to standard Knoppix, two Ubuntu chroots may be useful.

Did all the setup under 64-bits Ubuntu 12.04. Used debootstrap and created a minimal 64-bits Linux install, installed qemu, got a few packages along with that :) Chrooted into the install directory in Knoppix, after doing a bit of preparation

Code:

---


sudo su

# Bind-mount necessary directories
 for d in dev dev/shm dev/pts sys proc home tmp
    do mount /$d --bind ubu-precise1204/$d; done

# Get right /etc/mtab
 ln -s /proc/mounts ubu-precise1204/etc/mtab

# Do the chroot
 chroot ubu-precise1204 /bin/bash

# Run 64-bits qemu
qemu-system-x86_64 -machine accel=kvm -hda /dev/sda -m 2047 &

---

Gone through the Grub boot menu on the harddisk
* Usual install of Win 7 doesn't run this way, it starts booting, but gives up.
* Ubuntu 12.04 64-bits gets up and running, but there is something about network setup
* Knoppix 64-bits seems to run just fine.

This means, among other things:

* You will be able to run 64-bits Windows under Knoppix, in Qemu, provided you have a VM.
* You can install Oracle XE 11g in a 64-bits VM and run it as a server.
* You can install and run 64-bits SDKs, statistical programs (like R) etc.
* You don't have to install Ubuntu more than once + the debootstrap version, to use it fully
* You don't strictly have to care much about 64-bits troubles in Knoppix, go to the chroot instead.
* It should be portable: ca 600MB for 64-bits qemu directory uncompressed, ca 1.2 GB (so far) for 32-bits tizen directory
* Don't know how smart it is to include chroot directories in persistent store,but it is possible.