Looking at search traffic, it seems the following netplan issues get people frequently. No tabs in YAML Problem: netplan prints an error message like this: Invalid YAML at //etc/netplan/10-bad.yaml line 6 column 0: found character that cannot start any token Solution: You have a tab in your YAML file. Remove the tab and try again. There will eventually be better error messages for this - PR#12 or PR#18 , but they haven't landed as of June 2018. mapping values are not allowed in this context Problem: netplan prints an error message like this: Invalid YAML at //etc/netplan/10-bad.yaml line 3 column 12: mapping values are not allowed in this context Cause: Netplan parses YAML with libyaml, which has some rather obtuse error messages. As far as I can tell, this is caused when you have a YAML file where: you have begun a mapping. As of Bionic, netplan recognises networks, match, nameservers, routes, routing-policy, access-points, parameters...