What does mounting in docker mean?

In docker, mounting is to overwrite the files or folders in the container with the files or folders of the host, which can realize automatic two-way data synchronization between the host and container directories (files).

The operating environment of this tutorial: linux5.9.8 system, docker-1.13.1 version, Dell G3 computer.

Docker mounting is to overwrite the files or folders in the container with local files or folders.

Function:

We use cp command to realize data transfer, this method is more troublesome;

We mount through the container directory, which can realize the host and container Automatic two-way data synchronization of directories can easily realize code upload, configuration modification, log synchronization and other needs.

Note: When docker mounts the configuration file, be careful not to write the wrong content of the configuration file to be mounted, otherwise the container will not start after the container is created.

Folder mounting Loading the folder on

host will definitely overwrite the folder in the container:

##hostcontainermount resultThe folder does not exist/The folder exists but is emptyThe folder does not exist/Exists but is empty/Exists and is not emptyThe file in the container is overwritten (emptied) The folder exists and is not empty The folder does not exist/exists but is empty/exists and is not empty The contents of the folder in the empty container are overwritten (the original content is cleared and overwritten with the contents of the folder on the host)

• Not allowed If an existing folder or an existing empty folder is mounted into the container, the corresponding folder in the container will be cleared.

  
  

• Non-empty folders will be overwritten when mounted into the container. The original folder in the container

File mounting

The biggest difference between file mounting and folder mounting is:

• docker prohibits mounting files that do not exist on the host to files that already exist in the container

• File mounting will not affect other files in the same folder Any impact on the file

• Mounting an existing file into the container will overwrite the corresponding file in the container. If the file does not exist, create a new one

Summary

The files on the host will definitely overwrite the files in the container

##hostNon-existent file Existing files

container	mount result
Existing file	Prohibited behavior
Non-existing files/already existing files	Add/overwrite (if the directory does not exist, the directory will be created)

Application Scenario

From the above analysis, it can be seen that folder mounting covers files in units of the entire folder, so it can be used when a large number of files need to be mounted into the container. , in addition, if you mount an empty folder or a non-existent folder, it is usually used in reverse: that is, after the container is started, some files (such as logs) may be generated under the folder of the mount point in the container. At this time , you can see it directly in the folder on the corresponding host.

File mounting will only overwrite a single file and will not affect other files in the same folder in the container. It is often used to mount configuration files to dynamically modify the default configuration at runtime.

Recommended learning: "

docker video tutorial

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