Qemu on Linux

Computing: Linux: Qemu: on Linux

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This article is about setting up and running the Qemu emulator on Linux.

Reference

• Qemu manpage

Notes

When Bochs mysteriously stopped being able to run Win98, I found that Qemu was able to use the exact same .img file Bochs had been using, and it did manage to load Win98 quite easily. It would appear, then, that the setup for Qemu on Linux is probably quite similar to that of Bochs.

Current issues

• 2005-12-29 Current repository version of Qemu no longer says "warning: could not open /dev/net/tun: no virtual network emulation", but still can't see anyone on network except the local (virtual) machine. DHCP is not fetching an IP address.
• Need to figure out how to mount an .img file -- although it's probably not safe to write to an .img while it's in use by the emulator, so this actually wouldn't be all that useful once you've got a bootable, networked OS. Networking is the way to exchange files.

Problems/Solutions

• Problem: "warning: could not open /dev/net/tun: no virtual network emulation"; Solution:
  • as root, run "modprobe tun"; if no error, then the tun module has been installed successfully
  • "ls /dev/net/tun" to make sure the device has been created
  • Try qemu again. If the console asks for a password for "/etc/qemu-ifup", on Ubuntu the password it wants is your user password (not sure if this must be the user who installed qemu or the user who is running qemu; perhaps they have to be the same?); this may be different for other distros
  • However, the network card may still not work at this point; see Current Issues above.

Other stuff

The sample /etc/qemu-ifup file which comes with linux-test-*.tar.gz:

#!/bin/sh
sudo /sbin/ifconfig $1 172.20.0.1