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With the adoption of systemd, there is now a centralized mechanism for the creation of temporary files and directories. A service wishing to use this method can remove mkdir commands in its own startup script and instead place a .conf file in /etc/tmpfiles.d, /run/tmpfiles.d, or /usr/lib/tmpfiles.d, with Ubuntu services seeming to prefer the last option.

The format of these files is the following:

  #Type Path        Mode UID  GID  Age Argument
  d     /run/user   0755 root root 10d -
  L     /tmp/foobar -    -    -    -   /dev/null