rhel7.2: systemd hangs during system shutdown in rescue mode

Issue

systemd hangs during system shutdown in rescue mode.

This issue could happen not only during system shutdown, but also during system boot and even in normal system operation.

• If the issue occurs during system boot or system shutdown, system boot or system shutdown stops and doesn't complete.
• If the issue occurs in normal system operation:
  • systemd becomes unresponsive and users cannot make any system operations requiring systemd such as user logins, system shutdowns, systemd service operations, and many other operations done via systemctl command.
  • To reboot the system, we have to enforce a reset in executing systemctl --force --force reboot. If we kill the systemd process, a kernel panic occurs because it is the init process with PID 1.