5.13. /var/run : Run-time variable data

5.13.1. Purpose

This directory was once intended for system information data describing the system since it was booted. These functions have been moved to /run; this directory exists to ensure compatibility with systems and software using an older version of this specification.

5.13.2. Requirements

In general, the requirements for /run shall also apply to /var/run. It is valid to implement /var/run as a symlink to /run.

The utmp file, which stores information about who is currently using the system, is located in this directory.

Programs should not access both /var/run and /run directly, except to access /var/run/utmp. [45]

[45] This is to prevent confusion about where transient files are located. In general, a program should use either /var/run or /run to access these files, not both.