How Do You Pause and Resume Docker Containers?

Pausing and resuming Docker containers is very important for managing containers. This lets us stop a container for a while without fully stopping it. This is helpful to save system resources or for debugging. When we pause a container, the state of the application and its processes stay the same. This way, we can free up CPU cycles.

In this article, we will learn how to pause and resume Docker containers. We will also look at the commands we need to use. We will explain what happens to running processes when we pause a Docker container. We will see the differences between stopping and pausing containers. We will also learn how to monitor paused containers. Finally, we will answer some common questions about managing Docker containers. Here are the topics we will cover:

How Can You Effectively Pause and Resume Docker Containers?
What Are the Commands to Pause Docker Containers?
How Do You Resume Paused Docker Containers?
What Happens to Running Processes When You Pause a Docker Container?
Can You Stop and Start Docker Containers Instead of Pausing?
How to Monitor Paused Docker Containers?
Frequently Asked Questions

For more information on Docker and what it can do, we can check these related articles: What Is Docker and Why Should You Use It? and How to Stop and Start Docker Containers.

What Are the Commands to Pause Docker Containers?

We can pause a running Docker container by using the docker pause command. This command sends a SIGSTOP signal to the processes in the container. This will pause them. Here is how the command looks:

docker pause <container_name_or_id>

Example

If we want to pause a container called my_container, we can run:

docker pause my_container

We can also pause many containers at the same time. We just need to list their names or IDs with spaces in between:

docker pause container1 container2

Verifying the Pause State

To check if a container is paused, we can use the docker ps command. We add the -f filter to look for the status:

docker ps -f "status=paused"

This command will show us all containers that are paused right now.

For more information on managing containers, we can look at How to Stop and Start Docker Containers.

How Do You Resume Paused Docker Containers?

We can resume a paused Docker container using the docker unpause command. This command helps to start the processes in a container that we paused before with the docker pause command.

Syntax

docker unpause <container_id_or_name>

Example

If we have a paused container called my_container, we can resume it by typing:

docker unpause my_container

Verification

After we run the unpause command, we can check if the container is running again. We do this by checking the status with:

docker ps

This command lists all active containers. We can see if my_container is now running.

What Happens to Running Processes When You Pause a Docker Container?

When we pause a Docker container, all processes inside that container stop. This means the container’s work is put on hold for a bit. It does not use any CPU resources during this time. The processes save their state, so we can start them again later without losing any data.

Key Points:

Process Suspension: The pause command tells the container’s processes to stop working. They stay in memory but do not use CPU cycles.
Memory State: The memory and resources for the paused container stay the same. This helps us to start it quickly later.
I/O Operations: Any I/O work that was happening will also pause. We cannot read or write anything until we resume the container.
Network Connections: Current network connections will stay, but they will not send or receive data while the container is paused.
Resource Management: Pausing containers helps us manage system resources. This is especially helpful on servers that run many containers.

Example Command:

To pause a running Docker container, we can use this command:

docker pause <container_id_or_name>

To start the container again, we use:

docker unpause <container_id_or_name>

This way, we can manage running processes well without stopping or restarting the entire container. For more details on managing Docker containers, we can check out How to Stop and Start Docker Containers.

Can You Stop and Start Docker Containers Instead of Pausing?

Yes, we can stop and start Docker containers instead of pausing them. When we stop a Docker container, it stops all the running tasks. This frees up system resources. The container saves its state. Later, we can restart it and continue from where it was.

To stop a Docker container, we use this command:

docker stop <container_id>

We need to replace <container_id> with the ID or name of the container we want to stop.

To start a stopped Docker container, we use:

docker start <container_id>

This command will continue the container’s tasks from the point it was stopped.

Difference Between Pausing and Stopping

Pausing: It stops all tasks in a container for a while. We can resume later without losing the current state.
Stopping: It ends the container’s tasks completely. We need to restart it to continue working.

Using docker stop and docker start is good when we want to stop everything. On the other hand, docker pause and docker unpause are better for short breaks without losing the state.

For more info about managing Docker containers, we can check the article on how to stop and start Docker containers.

How to Monitor Paused Docker Containers?

We can monitor paused Docker containers using a few simple Docker commands and tools. This helps us check the status, resource use, and logs of our containers. Here are some easy methods:

Check Container Status: We can use this command to see all containers and their statuses. This includes containers that are paused.
```
docker ps -a
```
This command shows the status as Paused for any containers that are paused right now.
Inspect a Specific Container: If we want to get more details about a paused container, we can use:
```
docker inspect <container_id>
```
We just need to replace <container_id> with the real ID or name of the paused container.
Resource Usage Monitoring: When a container is paused, it does not use CPU. But it still uses memory. We can check memory use by using:
```
docker stats --no-stream
```
This command gives us a quick look at resource use for all containers, including those that are paused.
View Logs: To see the logs of a paused container, we can run:
```
docker logs <container_id>
```
This command shows the logs that were made before the container was paused. We should note that logs will not change while the container is paused.
Using Third-Party Tools: We can also think about using tools like Prometheus, Grafana, or cAdvisor. These tools help us see a full view of our Docker containers, even those that are paused.

By using these methods, we can monitor paused Docker containers well and make sure they work as they should. For more info on managing Docker containers, we can check out how to stop and start Docker containers.

Frequently Asked Questions

1. How do we pause a running Docker container?

We can pause a running Docker container easily. We just use the docker pause command and then add the container ID or name. This command will pause all processes in the container. It lets us stop its work for a while without shutting it down completely. For example, we can run:

docker pause <container_id_or_name>

This command helps us manage resources better while keeping the container’s state.

2. What is the difference between pausing and stopping a Docker container?

Pausing a Docker container means we stop all its processes for a short time. We can resume them later without losing their state. But when we stop a container with the docker stop command, it shuts down completely. All processes end, and resources free up. When we resume a paused container, it goes back to how it was. A stopped container needs to start fresh.

3. Can we monitor the status of paused Docker containers?

Yes, we can check the status of paused Docker containers using the docker ps command. This command shows all containers and their status, including paused ones. We can find paused containers in the list. If we want more details about a specific container, we can use:

docker inspect <container_id_or_name>

4. What happens to data while a Docker container is paused?

When we pause a Docker container, all the processes inside it stop, but the container’s data and filesystem stay safe. This means any data in memory or transactions are paused, but nothing gets lost. Pausing is a good way to manage resources without losing what the application inside the container is doing.

5. Is it better to pause or stop a Docker container?

Choosing to pause or stop a Docker container depends on what we need. Pausing is good for a short break while keeping the container’s state. This is helpful during maintenance or when fixing issues. Stopping a container is better when we do not need it anymore because it frees up system resources. We should think about our needs to pick the best way to manage our Docker containers.