# `/run` (runtime data)
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 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](https://specifications.freedesktop.org/basedir-spec/latest/), these paths should not be referenced directly but rather via the `$XDG_RUNTIME_DIR` environment variable.