Pam module to create /run/user/<uid> directory.
It is useful sometimes to create this directory before pam_systemd and systemd-logind create it.
Enable pam module with
session optional pam_xdg_runtime_dir.so debug
added to the pam_stack.
Enable this pam module in /etc/pam.d/sshd before pam_systemd to create the directory and populate it with a
kerberos credential. See the pam_krb5_cc_move pam module.