System services fail with "Failed to set up network namespacing: No space left on device"

Issue

• Some system services such as irqbalance.service and systemd-hostnamed.service fail with the following error message

  # systemctl status irqbalance.service --no-pager --full 
  × irqbalance.service - irqbalance daemon
       Loaded: loaded (/etc/systemd/system/irqbalance.service; enabled; preset: enabled)
       Active: failed (Result: exit-code) since [...]
  [...]
  [...] systemd[1]: Started irqbalance daemon.
  [...] systemd[733]: irqbalance.service: Failed to set up network namespacing: No space left on device
  [...] systemd[733]: irqbalance.service: Failed at step NETWORK spawning /usr/sbin/irqbalance: No space left on device
  [...] systemd[1]: irqbalance.service: Main process exited, code=exited, status=225/NETWORK
  [...] systemd[1]: irqbalance.service: Failed with result 'exit-code'.
  
  # systemctl status systemd-hostnamed.service --no-pager --full 
  × systemd-hostnamed.service - Hostname Service
       Loaded: loaded (/usr/lib/systemd/system/systemd-hostnamed.service; static)
      Drop-In: /usr/lib/systemd/system/systemd-hostnamed.service.d
               └─disable-privatedevices.conf
       Active: failed (Result: exit-code) since [...]
  [...]
  [...] systemd[1]: Starting Hostname Service...
  [...] systemd[1492]: systemd-hostnamed.service: Failed to set up network namespacing: No space left on device
  [...] systemd[1492]: systemd-hostnamed.service: Failed at step NETWORK spawning /usr/lib/systemd/systemd-hostnamed: No space left on device
  [...] systemd[1]: systemd-hostnamed.service: Main process exited, code=exited, status=225/NETWORK
  [...] systemd[1]: systemd-hostnamed.service: Failed with result 'exit-code'.
  [...] systemd[1]: Failed to start Hostname Service.