Incorrect hypervisors and virtual Facts with Unsupported Container Runtime Warning in Docker

[molhamalnasr]

Describe the Bug

When running Puppet Facter inside a Docker container, the hypervisors and virtual facts are incorrectly set. Additionally, a warning is displayed:
Warning: Facter: Container runtime, 'docker', is unsupported, setting to, 'container_other'.

Example Output:

# facter -p hypervisors
[2024-11-27 13:49:35.972235 ] WARN Facter::Resolvers::Containers - Container runtime, 'docker', is unsupported, setting to, 'container_other'

# facter -p virtual
[2024-11-27 13:49:42.488042 ] WARN Facter::Resolvers::Containers - Container runtime, 'docker', is unsupported, setting to, 'container_other'
container_other

Expected Behavior

In previous versions (e.g., Tag 4.7.0), the hypervisors and virtual facts returned the correct values:

# facter -p hypervisors
{
  docker => {
    id => "<STRING_ID>"
  }
}

# facter -p virtual
docker

Steps to Reproduce

1. Run Puppet Agent/Facter inside a Docker container.
2. Execute the command facter -p hypervisors or facter -p virtual.

Environment

• Version: Puppet Agent 7.32.1
• Platform: Ubuntu 24.04
• Facter Version: 4.8.0

Additional Context

After debugging the repository, I identified the root cause in the following line within lib/facter/resolvers/containers.rb:

read_environ(fact_name) || read_cgroup(fact_name)

The call to read_environ(fact_name) always returns a value, which prevents read_cgroup(fact_name) from being executed. This causes the resolver to misidentify the container runtime and set incorrect values for the hypervisors and virtual facts.

[mhashizume]

Thank you for reporting this @molhamalnasr , we have added this issue to our backlog.

[github-actions]

Migrated issue to FACT-3488

[joshcooper]

@molhamalnasr I can't reproduce this ever working. In particular, read_environ returns nil, because there isn't a container environment variable defined for pid 1:

❯ docker run -it ubuntu:noble cat /proc/1/environ 
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/binHOSTNAME=00ddb9b41876TERM=xtermHOME=/root

Also it doesn't appear any version of facter correctly detects those facts:

❯ docker --version
Docker version 27.3.1, build ce12230

❯ docker run -it ubuntu:noble /bin/bash -c 'apt-get update > /dev/null && apt-get install -y ruby > /dev/null && gem install --no-document --version 4.7.0 facter && facter hypervisor virtual'
debconf: delaying package configuration, since apt-utils is not installed
Fetching thor-1.2.2.gem
Fetching hocon-1.4.0.gem
Fetching facter-4.7.0.gem
Successfully installed thor-1.2.2
Successfully installed hocon-1.4.0
Successfully installed facter-4.7.0
3 gems installed
hypervisor => 
virtual => physical

❯ docker run -it ubuntu:noble /bin/bash -c 'apt-get update > /dev/null && apt-get install -y ruby > /dev/null && gem install --no-document --version 4.8.0 facter && facter hypervisor virtual'
debconf: delaying package configuration, since apt-utils is not installed
Fetching facter-4.8.0.gem
Fetching thor-1.2.2.gem
Fetching hocon-1.4.0.gem
Successfully installed thor-1.2.2
Successfully installed hocon-1.4.0
Successfully installed facter-4.8.0
3 gems installed
hypervisor => 
virtual => physical

❯ docker run -it ubuntu:noble /bin/bash -c 'apt-get update > /dev/null && apt-get install -y ruby > /dev/null && gem install --no-document --version 4.9.0 facter && facter hypervisor virtual'
debconf: delaying package configuration, since apt-utils is not installed
Fetching facter-4.9.0.gem
Fetching thor-1.2.2.gem
Fetching hocon-1.4.0.gem
Successfully installed thor-1.2.2
Successfully installed hocon-1.4.0
Successfully installed facter-4.9.0
3 gems installed
hypervisor => 
virtual => physical

❯ docker run -it ubuntu:noble /bin/bash -c 'apt-get update > /dev/null && apt-get install -y ruby > /dev/null && gem install --no-document --version 4.10.0 facter && facter hypervisor virtual'
debconf: delaying package configuration, since apt-utils is not installed
Fetching hocon-1.4.0.gem
Fetching facter-4.10.0.gem
Fetching thor-1.2.2.gem
Successfully installed thor-1.2.2
Successfully installed hocon-1.4.0
Successfully installed facter-4.10.0
3 gems installed
hypervisor => 
virtual => physical

EDIT: The /proc/1/environ method looks specific to starting a container via systemd https://github.com/systemd/systemd/blob/16ac586e5a77942bf1147bc9eae684d544ded88f/docs/CONTAINER_INTERFACE.md?plain=1#L415-L417