Why can docker achieve isolation?

Docker is a virtualization technology that can be used to deploy and manage applications quickly and efficiently. Its core concept is to package the application and its dependent libraries, frameworks, etc. into a portable container, avoiding dependencies between the application and the system and ensuring that the application can run in any environment.

Docker can achieve isolation in three main aspects:

1. Namespace

Docker uses the namespace technology provided by Linux to ensure the isolation between containers. By using different namespaces, Docker can isolate resources such as different processes, file systems, networks, and ports.

For example, each container has its own file system, and each container can only see their own file system and cannot access the file systems of other containers. This ensures that each container's applications and data are isolated and do not interfere with each other.

2. Control Group

Docker also uses Linux’s control group (cgroup) technology to manage the resource usage of containers. By using cgroups, Docker can control the CPU, memory, disk and other resources used by containers and limit their usage. This ensures that resources between containers do not conflict with each other and prevents the entire system from crashing due to a container taking up too many resources.

For example, you can limit the CPU time and memory size used by a container to avoid a container taking up too much CPU and memory, causing applications in other containers to respond slowly or crash.

3. File system

Docker also provides an independent file system for each container and uses Union File System (UnionFS) technology to combine the file system of the host system and the container file systems are merged. This ensures that each container has its own independent file system and does not affect the file systems of other containers and the host system.

For example, different system libraries can be used in a container without affecting the libraries of other containers and the host system. This ensures that applications between containers do not have any dependencies, preventing containers from running properly due to dependencies.

To sum up, Docker can successfully achieve isolation mainly by utilizing the namespace, control group and file system technologies provided by Linux. These technologies enable each container to have independent processes, file systems and resource restrictions, avoiding interference between containers and host systems, ensuring that applications can run efficiently.

The above is the detailed content of Why can docker achieve isolation?. For more information, please follow other related articles on the PHP Chinese website!