Ansible: Detect and differ between LXC containers and hosts

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Published on June 13th 2018 - Listed in Linux Ansible LXC


While looking for a way to handle certain tasks differently inside a LXC container and on a (physical) host, I first tried to use ansible variables based on some hardware. 

But the problem, as you might know, is that LXC containers basically see the same hardware as the host because they use the same kernel (there is no hardware virtualization layer in between).
Note: That's what makes the containers much faster than VM's, just sayin'.

So checking for hardware will not work, as both host and container see the same:

$ ansible host -m setup | grep ansible_system_vendor
        "ansible_system_vendor": "HP",

$ ansible container -m setup | grep ansible_system_vendor
        "ansible_system_vendor": "HP",

When I looked through all available variables coming from "-m setup", I stumbled across ansible_virtualization_role at the end of the output. Looks interesting!

$ ansible host -m setup | grep ansible_virtualization_role
        "ansible_virtualization_role": "host",

$ ansible container -m setup | grep ansible_virtualization_role
        "ansible_virtualization_role": "guest",

Awesome!


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Comments (newest first)

huj from wrote on Apr 24th, 2019:

Mine just says NA for both - it's a VPS that has LXC on so the method is biased