/run (runtime data)
System components use the /run directory to store small
amounts of runtime data, such as socket files. It is a tmpfs file system,
writable only by privileged programs. The legacy /var/run path is a
symbolic link to /run.
The /run/log directory can hold logs before they are written to
/var/log, or before the /var/log file system is
available.
The /run/user/ path contains per-user runtime directories:
individual tmpfs file systems that systemd mounts when a user logs
in and removes when the user logs out. Reference them through the
$XDG_RUNTIME_DIR environment variable, as described in the XDG Base Directory
Specification
