title: why `docker run -d centos tail -f /dev/null` command can keep the docker container running in the background?
body: <p><a href="https://i.stack.imgur.com/A6HKk.png" rel="nofollow noreferrer">enter image description here</a></p>
  <p>This evening, by checking the data, I learned that to make the docker container run in the background, you should add <code>tail - f /dev/null</code> after the command. However, I don't understand the meaning of each letter in the command <code>tail - f /dev/null</code>. I only know that it can make the docker container run in the background. I want to know the meaning of each letter in the command <code>tail - f /dev/null</code>,Thanks in advance.</p>