I'm not sure if there's something it's not doing here that is failing, or if it's just a spurious error, but when attempting to set the hostname on the most recent rolling release, the following is observed:
vyos@cr01b-vyos:~$ configure [edit] vyos@cr01b-vyos# set system host-name cr01b-vyos.int.trae32566.org [edit] vyos@cr01b-vyos# commit [ system host-name cr01b-vyos.int.trae32566.org ] Fatal: Unable to generate local temporary file in directory '/run/powerdns': No such file or directory [edit] vyos@cr01b-vyos# comp No changes between working and active configurations vyos@cr01b-vyos# run show host name cr01b-vyos.int.trae32566.org