O desligamento cria um arquivo /etc/nologin
quando chamado para interromper o login de novos usuários (não raiz) assim que o desligamento é programado. Remover o arquivo deve permitir que os usuários façam o login.
If shutdown is called with a delay, it creates the advisory file /etc/nologin which causes programs such as login(1) to not allow new user logins. Shutdown removes this file if it is stopped before it can signal init (i.e. it is cancelled or something goes wrong). It also removes it before calling init to change the runlevel.