Question 27118 in CentOS Question posted in
The official documentation can be found here.

why `docker run -d centos tail -f /dev/null` command can keep the docker container running in the background?

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This evening, by checking the data, I learned that to make the docker container run in the background, you should add tail - f /dev/null after the command. However, I don’t understand the meaning of each letter in the command tail - f /dev/null. 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 tail - f /dev/null,Thanks in advance.

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2

Answers


  1. 0

    There is a typo in your command. Remove the whitespace between – and f then it should work.

    tail is responsible to read the last 10 lines of a file -f parameter means follow all lines which will be added to the file.

    This is the reason why the terminal will stay open.

    /dev/null is a Linux device.

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  2. 0

    I think you mean tail -f /dev/null

    From man tail:

    DESCRIPTION
       Print the last 10 lines of each FILE to standard output.
.
.
.
-f, --follow[={name|descriptor}]
          output appended data as the file grows;

          an absent option argument means 'descriptor'

    /dev/null is a virtual device file that will appear to tail as if it were a "normal" file.

    In plain English, this will make tail keep waiting for new data in /dev/null, but there will never be any since it’s a special type of device (essentially a black hole).

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