Docker has revolutionized the way we develop and deploy applications, offering an efficient method to package applications into containers. These containers are isolated environments that contain everything an application needs to run, including the filesystem. In this guide, we will explain how you can access the Docker container filesystem on Ubuntu 20.04.
To access the Docker container filesystem on Ubuntu 20.04, you can use various methods such as exporting the entire filesystem, mapping specific directories, using docker exec to get a shell, or copying files using docker cp.
Understanding Docker Filesystem
Before we dive in, it’s important to understand that each Docker container has its own filesystem, separate from the host and other containers. This filesystem is created from a Docker image, which is a lightweight, standalone, and executable software package that includes everything needed to run a piece of software.
Accessing Docker Container Filesystem
There are several methods to access the filesystem of a Docker container. We will cover the most common ones: exporting the entire filesystem, mapping specific directories, using docker exec to get a shell, and copying files using docker cp.
Exporting the Entire Filesystem
To export the entire filesystem of a Docker container to a .tar archive, you can use the docker export command. Here is an example:
docker export --output="container-name.tar" <container-name>In this command, --output or -o specifies the name of the file to which the filesystem will be exported. Replace <container-name> with the name of your Docker container.
Mapping Specific Directories
If you only need to access specific files or folders inside a container, it’s recommended to map them directly when starting the container using the -v or --volume flag. Here is an example:
docker run -d -v /path/to/data:/data <container-name>In this command, -d runs the container in detached mode, -v or --volume creates a bind mount. /path/to/data is the path on your host machine, and /data is the path in the container. Replace <container-name> with the name of your Docker container.
Using Docker Exec to Get a Shell
If you want to browse the files inside a running container, you can use the docker exec command to get a shell inside the container. Here is an example:
docker exec -it <container-name> /bin/bashIn this command, -it ensures that you get an interactive terminal. Replace <container-name> with the name of your Docker container.
Copying Files Using Docker Cp
If you want to copy a file from a container to your host machine, you can use the docker cp command. Here is an example:
docker cp <container-name>:/path/to/file /target/path/In this command, replace <container-name> with the name of your Docker container, /path/to/file with the path of the file in the container, and /target/path/ with the target directory on your host machine.
Conclusion
In this guide, we have covered multiple methods to access the filesystem inside Docker containers on Ubuntu 20.04. Remember, directly accessing or modifying the Docker managed files under /var/lib/docker is not recommended as it can lead to data loss. Always use the Docker provided commands and options to interact with your containers. Happy Dockering!
Yes, you can access the Docker container filesystem while the container is running. You can use docker exec command to get a shell inside the running container and browse the files.
Yes, you can export the entire filesystem of a Docker container using the docker export command. It will create a .tar archive containing the complete filesystem of the container.
Yes, you can access specific files or folders inside a Docker container by mapping them directly when starting the container using the -v or --volume flag. This creates a bind mount that allows you to access the specified files or folders.
You can copy files from a Docker container to your host machine using the docker cp command. Simply specify the container name, the path of the file inside the container, and the target directory on your host machine.
No, it is not recommended to directly access or modify Docker managed files under /var/lib/docker as it can lead to data loss. It is best to use the Docker provided commands and options to interact with your containers.
