cmaven

작업노트

:bulb: In Ubuntu / KVM / virt-manager environments, cloning a VM often causes a DHCP IP assignment failure where the new VM behaves like it shares the original’s IP. This post covers how to make both VMs receive distinct IPs.

[01] Environment and Symptom

Environment

  • Ubuntu 24.04
  • virt-manager
  • KVM
  • QEMU
  • virsh
  • libvirt

Symptom

  • Clone VM A into VM B
  • VM A receives 10.10.10.10 from the DHCP server
  • VM B brings its link UP but never receives an IP
  • virsh net-dhcp-leases default shows only VM A’s IP

Root Cause

On Linux, DHCP IP assignment is not based on MAC address by default — it’s based on machine-id. When you clone a VM, both VMs end up with the same machine-id.

[02] Change the VM’s machine-id



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# Remove the existing machine-id
sudo rm -f /etc/machine-id

# Generate a new machine-id
dbus-uuidgen --ensure=/etc/machine-id

# Verify
cat /etc/machine-id

[03] Verify After Change

Both the original and cloned VMs should now receive distinct IPs from DHCP.

참고