Netplan generates the wrong YAML value when setting activation-mode=off

[Isaac True]

When setting activation-mode=off on Ubuntu 20.04/Ubuntu Core 20, netplan generates the incorrect value in the YAML file (activation-mode: false), causing it to fail due to incorrect syntax.

$ sudo netplan set ethernets.eth0.activation-mode=off
Traceback (most recent call last):
  File "/usr/sbin/netplan", line 23, in <module>
    netplan.main()
  File "/usr/share/netplan/netplan/cli/core.py", line 50, in main
    self.run_command()
  File "/usr/share/netplan/netplan/cli/utils.py", line 247, in run_command
    self.func()
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 55, in run
    self.run_command()
  File "/usr/share/netplan/netplan/cli/utils.py", line 247, in run_command
    self.func()
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 126, in command_set
    self.write_file(subtree, hint + '.yaml', self.root_dir)
  File "/usr/share/netplan/netplan/cli/commands/set.py", line 193, in write_file
    libnetplan.netplan_parse(tmpp)
  File "/usr/share/netplan/netplan/libnetplan.py", line 64, in netplan_parse
    raise Exception(err.contents.message.decode('utf-8'))
Exception: /tmp/netplan-set_o73ewgp4/etc/netplan/50-cloud-init.yaml:4:24: Error in network definition: Value of 'activation-mode' needs to be 'manual' or 'off'
      activation-mode: false
                       ^

[Lukas Märdian (slyon)]

This seems to be due to the (old) Python YAML parser being in conflict with libnetplan's actual C YAML parser.

Apparently pyyaml interprets "off" as a boolean ('False') by default in yaml.safe_load(value) (`set_tree = self.parse_key(key, yaml.safe_load(value))`), while it is supposed to be an actual string ("off") for activation-mode.

Looks like it was broken ever since netplan set was introduced (v0.101) and just recently got fixed via https://github.com/canonical/netplan/pull/254 (https://github.com/canonical/netplan/commit/bdb4f9846c8f40275c09a28bed04d8436cbbeffc to be specific)

[Lukas Märdian (slyon)]

A quick workaround seems to be quoting the parameters like this:

netplan set "ethernets.eth0.activation-mode='off'"