The /run directory is used by system packages to store small
amounts of runtime data (such as socket files). It is a tmpfs file
system, and is writable only by privileged programs.
The /run/log directory can be used by system components to store
logs in, either before being written out to /var/log or before
the /var/log file system is available.
The /run/user/ path contains per-user runtime directories.
By default, these will be individual tmpfs file systems mounted
by systemd when the user logs in, and erased when the user
is no longer logged in. As per the
XDG Base Directory Specification$XDG_RUNTIME_DIR
environment variable.
