从 Linux 虚拟机如何检测/识别 Azure 平台

Question

Am looking for a unique way to identify that the Virtual machine (VM) is running on Azure or Hyperv. Something like all the VM's running only on Azure will have this identity. That too I need to know on VM bootup stage itself and not after VM is up and running. I want to mainly differentiate between a VM running on Azure and Hyper-v.

For example we can use PCI BUS ID 14145353(reading bus/pci/devices file) to detect VM runs on Hyper-v. I am looking for something similar for azure.

-Thanks

Answer 1

The option “unknown-245” is an Azure-proprietary option which only gets issued by an Azure DHCP server. Since in Azure you always will get an address via DHCP (static IPs are also managed by the DHCP and with the REST management API) you will always (and in theory only) get this option as part of the DHCP lease attributes when your machine runs in Azure.

You can create a bash-script such as the following one to detect if the option unknown-245 is available to have a first indicator of whether you run in Azure or not.

Ubuntu

if `grep -q unknown-245 /var/lib/dhcp/dhclient.eth0.leases`; then
    echo “Running in an Azure VM”
fi

For CentOS based virtual machines the DHCP lease options are indeed stored in the path /var/lib/dhclient/dhclient.leases (or in case of multiple network interfaces dhclient-eth0.leases whereas the part eth0 needs to be replaced with the networking interface device you're going to check against).

Therefore in a default configuration with just one ethernet adapter the script needs to be updated as follows to work inside of a CentOS virtual machine:

# manually start dhclient (seems to be a workaround)
dhclient

# then check against the lease files
if `grep -q unknown-245 /var/lib/dhclient/dhclient.leases`; then
   echo "Running in Azure VM"
fi

Another approach is reading the configuration from the Microsoft Azure Agent which is always installed on a Linux VM and try to reach it's ping-counterpart on the host-agent side. If a VM does not run in Azure, trying to reach the host-agent end-point would always result in a timeout. Here's a sample script for doing so:

curl –connect-timeout 1 `grep FullConfig /var/lib/waagent/GoalState.1.xml | perl -pe ‘s/<.?FullConfig>//g; s/\s//g’` && echo azure || echo no-azure

source and source

Answer 2

You can go through /var/log/waagent.log and look for a recent Retrieved GoalState from Windows Azure Fabric or, alternatively, look for the fabric endpoint IPv4 address and check if it's reachable. A less friendly but equally effective way is to look at your latest DHCP lease and look for option 245.

Answer 3

The answer may be late but as it is the case for Cloud Init ( here ) the detection is done by looking at the chassis asset tag by running:

dmidecode --string chassis-asset-tag

Or by looking directly at the file:

/sys/devices/virtual/dmi/id/chassis_asset_tag

If the value returned is equal to 7783-7084-3265-9085-8269-3286-77 it means you are running on the azure platform.