Dockerfile ＞Docker Image ＞ Docker Container | Beginners Hands-On | Step by Step
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- เผยแพร่เมื่อ 15 มี.ค. 2023
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Last session • How to setup and use D...
STEPS
Create a Dockerfile
Add instructions in Dockerfile to create Docker image
Run Dockerfile to create Docker image
Run Docker image to create Docker container
Access the application running in Docker container
Dockerfile ＞ Docker Image ＞ Docker Container ＞ Access the App
Step 1 - Create a new directory mkdir myapp
cd myapp
Step 2 - Create a file called "index.html" echo "Hello, world!" ＞ index.html
Step 3 - Create a file named Dockerfile touch Dockerfile
Step 4 - Open the "Dockerfile" file in a text editor and add the following lines:
FROM nginx
COPY index.html /usr/share/nginx/html
This Dockerfile defines a new Docker image that
- uses the official nginx image as a base
- then copy the index.html file to the appropriate location in the image
A Dockerfile is a text file with instructions to build a Docker Image
When we run a Dockerfile, Docker image is created
When we run the docker image, containers are created
Step 5 - Start docker & Build docker image from dockerfile
docker build -t myapp .
This command builds a new Docker image with the tag "myapp" using the Dockerfile in the current directory.
Step 6 - Run docker container from the image
docker run -p 8080:80 myapp
This tells Docker to run the myapp container and map port 8080 on your local machine to port 80 inside the container
Step 7 - Access the app
Open a web browser and navigate to localhost:8080 to see the "Hello, world!" message displayed in your web browser.
If you are using AWS EC2 Linux, you will need to make sure that the security group for your AWS Linux instance allows inbound traffic on port 8080 (or whichever port you chose to map to port 80 inside the container).
Here's how to modify the security group:
Open the Amazon EC2 console at console.aws.amazon.com/ec2/.
In the navigation pane, choose "Instances".
Select your AWS Linux instance in the list.
Choose the "Security" tab in the bottom pane.
Select the security group associated with your instance and choose the "Edit inbound rules" button.
Add a new rule with the following settings:
Type: "Custom TCP Rule"
Protocol: "TCP"
Port Range: "8080" (or whichever port you chose to map to port 80 inside the container)
Source: "0.0.0.0/0" (or restrict the source IP address range to your specific needs)
After modifying the security group, you should be able to access the web page served by your Docker container by navigating to ＜Public_IP_of_your_instance＞:8080 in a web browser.
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A straight-to-the-point tutorial! Thanks for your service in the spirit of betterment. Your tutorial is a great testament to the power of sharing knowledge, and helping others to gain an edge.
Thanks for the kind words
This is amazing. I was trying EC2 instance first time to have docker run on it and this video made all my concepts very clear. Thanks for covering the security groups.
You're very welcome Niharika
Thanks Raghav, your way of explanation is simple and easy to understand. Thank you so much for your valuable contributions to people like me who are learning from basics.
Hi Sangati, thanks a lot for your kind words
Very good video that goes through all steps. Better than some professional teaching videos that do not explain details. Thank you, good job!
Glad it was helpful Reza
Thank you, Raghav. This was perfect for me! You were very clear and thorough. Great job!
You're very welcome!
Thanks, it really helps me to understand better the whole process of docker image and container👍
Glad it was helpful Akhror
I had no idea about Dockerfile. Your session gave me a big support and confidence to write a dockerfile. Thank you very much.
Great to know this Preethi
Clear and straight to the point. Thank you! 😊
Thanks
Explained in a very simple language. Thank you.
Most welcome Rohit
This is so far the best video on youtube with simple and straight to the point explanation. Thank you sir. I have subscribed
Most welcome
Thank you very much for this video Raghav. It was very great to understand and learn. Not even GUVI classes taking this much effective classes.
Glad to know it helped
Thank you for another perfectly explained video.... and thank you for keeping it simple and explaining even the small details.. some of us need that. Kudos to you!
You're very welcome
VEry very useful video here. Was looking for complete explanation and got clear answers to my current queries. Thanks for the video.
Glad it was helpful Mike
Randomly I got this video for Docker file, the way of teaching and pace of teaching is really good and appreciable. Thank you for such content I am following you from now and will see all the required videos on devops...
Most welcome.. Glad it was helpful
Thanks Raghav, your explanation helped me understand way better.
Most welcome Brandon
Thank you this helped me understand an area I was stuck on
Glad it helped Gavin
Great Playlist, Thanks Raghav your explanation is very good and really helpful to understand. Thanks a lot for this.
Most welcome Tarun
Thank you so much sir...🙂🙂
Your way of explaining is too good .. anyone can understand these lessons (without IT background also)
So nice of you Sravani
Thanks so much raghav best example have seen in the form of basic learning
So nice of you Bunny
Amazing! so well explained in a simple language for beginners like me to fully understand.
Glad it was helpful Laurencia.. humbled
Amazing docker presentation - especially how it can be linked to azure
Glad it was helpful Nagendra
Very simple and effective video. Thanks
Glad it was helpful Vijay
Thank you very much sir for this video. I've learnt new things from you. Thank you.
You are very welcome Blynk
Amazing!!.. I really liked your explanation
Glad to hear that Supriya, thanks
Sir. Its really helpful for the community..!!! 👏 👏 Especially for the people like me who are slow learners
Glad to hear that Rekha
Well Explained. thanks for sharing
Most welcome Maskawath
Really good explanation and i got a clear picture of the docker topic
Great to know this Chandrasekhar
Very good explanation, thanks.
Glad it was helpful!
Thanks. It is really helpful. Please share similar video while working on windows system. Or display parallel windows commands
Sure Renuka, can check some videos here - automationstepbystep.com/
although when you work in real world projects, mostly it will be a Linux system that will be used
I REALLY ENJOY IT, I NOW KNOW THE DIFFERENCES
Glad it helped Gody
Great tutorial for beginners
Glad it was helpful Djamol
worked perfectly thanks so much
You're welcome!
great video bro! thanks a lot!
Glad it helped
You are great teacher
Thank you! 😃
Your explain very clear crystal
Thanks
Thank you!
You're welcome
Very nice & Informative
Thanks Sunil
Excellent explanation
Glad it was helpful
Very nice tutorial! :)
Glad you like it!
excellent explanation
Glad it helped
So crystal clear
Thanks a lot Srija
Excellent teaching Sir tq
You're most welcome Shankar
Great video👏
Thank you Premjith
Thanks a lot!
You're welcome!
Nice Presentation brother!
Thanks for watching Jahid
super thank you!
Most welcome
Nice explanation
Thanks and welcome madhava
grate thank you
Most welcome Harish
Thank you , it's the best simplest explanation ever ,
Most welcome Niki
Thanks for the explanation! I am working on the applicable where it will automatically open the reports after my tests but when creating pipeline through dockers it's opened So I have copied the results of html file created from docker image to local instance.
Now my question how to open the html content which copied from docker image using docker run
Durga
If you've copied an HTML file from a Docker image to your local instance and want to view it using `docker run`, here are a few approaches you can take:
1. Using an HTTP Server (e.g., Apache HTTPd):
- This method involves creating a Docker image based on an HTTP server (such as Apache HTTPd) and serving your HTML file through it.
- Here's a step-by-step guide:
1. Create a Dockerfile with the following content:
```Dockerfile
FROM httpd:2.4
COPY ./public-html/ /usr/local/apache2/htdocs/
```
2. Build the Docker image:
```
docker build -t my-apache2 .
```
3. Run the container:
```
docker run -dit -p 8080:80 --name my-running-app my-apache2
```
4. Your HTML page should now be available at [yourip:8080/public-html](yourip:8080/public-html) ¹.
2. Mounting a Volume:
- If you have the HTML file locally, you can mount it into a running container using the `-v` option.
- For example, if your HTML file is in the `/path/to/your/html` directory, you can run:
```
docker run --name some-nginx -v /path/to/your/html:/usr/share/nginx/html:ro -d nginx
```
- Replace `/path/to/your/html` with the actual path to your HTML file ².
3. Viewing HTML Source Inside the Container:
- If you want to view the HTML source code directly inside the container, you can install an editor (e.g., Vim) and use it to inspect the file.
- Execute the following commands within the container:
```
docker exec -u 0 -it /bin/bash
apt-get update
apt-get install vim
```
- Replace `` with the actual ID of your running container ⁴.
Choose the method that best suits your requirements, and you'll be able to view your HTML content from the Docker image
@@RaghavPal Thanks for the reply. Sure I will try any one method. You are my guru, I have learned so many tools from your videos
This was really helpful and well explain>
Thanks Tanveer
Simple as it can be, loved it. However, I find it kind of funny that you app was working on port 80, even though there wasn't any rule in your security group.
Thanks Billy... I believe it was open for all connections,
@@RaghavPal Regardless, it was a great walk through
Hope my mentor copy this video to take classes. Same format he was tech us today.
Hope it helps all
No any confusion, Easy to learn content. Thanks.
Glad to know this
Nice tutorial, i am confused in the last part where you added an inbound rule. What difference did that make?
Okay, that I had to do to open the port to be accessible from outside
Do a small security group tutorial and it will be easy for you to understand that part, it's not complicated but crucial
Thank you
You're welcome
Good 👍😊
Thanks Jayendiran
Thanks you
Most welcome
This is such a wonderful video. I followed along with you but i stopped step #5 because while running the docker build -t myapp i got errors. I think it could because i am using my work laptop. Then i tried using environmental variables for proxy still i get error. Can you please help
Suchismita
When encountering issues with Docker builds related to proxies, there are a few steps you can take to troubleshoot and resolve the problem:
1. Proxy Configuration:
- Ensure that your proxy settings are correctly configured on your laptop.
- Check if you need to set environment variables like `http_proxy` and `https_proxy` to point to your corporate proxy server.
2. Docker Proxy Configuration:
- Docker uses its own proxy settings, separate from your system's proxy.
- You can configure Docker to use your corporate proxy by modifying its configuration.
- Open the Docker preferences/settings and navigate to the Proxy section.
- Enter the proxy details (host, port, username, password) if required.
3. Docker Build Arguments:
- When building a Docker image, you can pass build arguments using the `--build-arg` flag.
- For example:
```
docker build --build-arg http_proxy=your.proxy:8080 --build-arg https_proxy=your.proxy:8080 -t myapp .
```
- Replace `your.proxy` and `8080` with your actual proxy details.
4. DNS Configuration:
- Sometimes DNS resolution can cause issues. Ensure that your DNS settings are correctly configured.
- You can try changing the DNS server in Docker settings to a reliable one (e.g., Google's public DNS: `8.8.8.8`).
5. Restart Docker Daemon:
- After making changes, restart the Docker daemon to apply the new settings.
- You can do this from the Docker preferences/settings.
6. Check Firewall Rules:
- Verify that your firewall or security software is not blocking Docker connections.
- Adjust firewall rules if necessary.
7. Test Connectivity:
- Test if you can access external resources (e.g., `ping google.com`) from within a running Docker container.
- If not, it might be related to proxy or DNS issues.
Remember that Docker builds happen in a separate environment (inside containers), so the proxy settings need to be propagated correctly.
..
Hi Raghav. I had a question. How can we run docker-compose.yml file in ec2 machine for Selenium. Can you tell the steps or create a video on the same.
Hi Arpit
Here are the steps on how to run a docker-compose.yml file in an EC2 machine for Selenium:
1. Create an EC2 instance.
2. Install Docker Engine and Docker Compose on the EC2 instance.
3. Copy your docker-compose.yml file to the EC2 instance.
4. Run the following command to start the Docker containers:
```
docker-compose up
```
The Docker containers will start and Selenium will be running on the EC2 instance.
Here are the detailed steps:
1. **Create an EC2 instance.**
Go to the AWS Console and click on the **EC2** service. Then, click on the **Launch Instance** button. Select the instance type and the operating system that you want to use. For this tutorial, we will use the **t2.medium** instance type and the **Ubuntu Server 20.04 LTS** operating system.
2. **Install Docker Engine and Docker Compose on the EC2 instance.**
Once the EC2 instance is up and running, you need to install Docker Engine and Docker Compose. To do this, run the following commands:
```
sudo apt update
sudo apt install docker.io
sudo apt install docker-compose
```
3. **Copy your docker-compose.yml file to the EC2 instance.**
The docker-compose.yml file is a configuration file that tells Docker how to start the Docker containers. You can create this file yourself or you can download it from a repository. Once you have the docker-compose.yml file, you need to copy it to the EC2 instance. To do this, you can use a file transfer utility like **FileZilla** or **WinSCP**.
4. **Run the following command to start the Docker containers:**
```
docker-compose up
```
This command will start the Docker containers that are defined in the docker-compose.yml file. Once the Docker containers are started, Selenium will be running on the EC2 instance.
I hope this helps
Thanks a Lot Raghav for the steps and prompt response!
hey, great video! I just have one question.
You didn't specify a SO for your image, normally we put this in the FROM command.
So, in this case, where is this image getting the operating system from? You didn'y specfiy the SO at any point.
Gustavo
You're correct, the Docker demo I provided did not explicitly specify a base image in the `FROM` command. This may cause confusion, as most Docker images are built upon existing base images.
In the specific case of the demo, the image was getting its operating system from the **scratch** image. The `scratch` image is a special reserved image in Docker that represents an empty filesystem. Using `FROM scratch` essentially instructs Docker to build the image starting from a completely blank slate.
While this is possible for very simple images, it's not a common practice for building production-grade Docker images. Most images rely on existing base images to provide essential libraries, utilities, and the underlying operating system.
For the sake of clarity and best practices, future demonstrations should explicitly specify a base image using the `FROM` command, such as:
```
FROM ubuntu:latest
```
This clearly indicates that the image is based on the latest version of Ubuntu and inherits its operating system and dependencies.
I apologize for the confusion caused by the previous demo. Thank you for pointing out the omission, as it helps ensure the information provided is accurate and helpful.
All well and good if you want to see Hello World! on the screen but how do you make it do anything useful? How do you get real applications inside the container that can be used like MQTT?
This was for beginners to get started and understand concepts with hands-on, will plan for more sessions
@@RaghavPal while it was informative it didn't go deep enough to be of any real use. What might be useful is an even higher level video that explains where these files fit into the scheme of docker. Then these instructions might make more sense.
I will try to do more videos on this
Sir!!!!!!!!!thankyou 😊😊😊😊
Most welcome Rajeswari
your teaching was super sir and how to write playbook in ansible make one vedieo sir
Sure I will Parameswari
Aslo please make a note Raghav, that I have asked you to make a video on how Code quality testing is done using SonarQube and Testing processes done in CI process in Automation of Devops process.
Please make sure to get it as per your free time.
Thank you
I will work on it Sangati
Thank you for consideration and will be waiting Raghav
Can u make video about how to lunch docker image or docker container in kubernetes cluster
I will plan Hareesh, Can check the existing Kubernetes videos here automationstepbystep.com/
@@RaghavPal thank you for responding sir
Thank you so much Raghav for this amazing tutorial. But i am unable to run it on localhost
Most welcome Manisha.. can check all the steps again.. also try some other online examples
Can we use multiple os in same docker image
No, it's not possible to directly run multiple operating systems within a single Docker image. Each Docker image is designed to encapsulate a single operating system and its associated environment.
At 9:49 you started the docker with command, can you please help me with macOS command to start the docker?
Shubham
Sure. Here are the macOS commands to start Docker:
1. Open a terminal window.
2. Type the following command:
```
docker start
```
This will start the Docker daemon.
If you want to start Docker in the background, you can use the following command:
```
docker start -d
```
This will start the Docker daemon and detach it from the terminal window.
You can also start Docker by specifying the name of the container that you want to start. For example, to start the container named `my-container`, you would use the following command:
```
docker start my-container
```
You can check if Docker is running by typing the following command:
```
docker ps
```
This will list all of the Docker containers that are running. If Docker is not running, you will see an empty list.
I hope this helps
I have a basic doubt if anyone can help... why do you even need to create a docker image for a .html file? if you create it here on a Linux EC2 machin and install it on a windows machine as it is... without creating a docker container... will it not work?
Dushyant
It's unlikely that an HTML file created on a Linux EC2 machine will function directly on a Windows machine without any additional steps, even if you avoid using Docker containers. Here's why:
Differences in environment:
Operating system: Each OS has its own file system structure, libraries, and executables. While HTML is a platform-agnostic language, scripts or functionalities embedded within the HTML might rely on specific Linux components unavailable on Windows.
Web server configuration: Even if the HTML itself renders, different web servers on Linux and Windows may interpret certain elements differently, leading to inconsistencies or errors.
Dependencies: Many modern web applications involve JavaScript frameworks, libraries, or databases. These dependencies might be packaged differently for Linux and Windows, requiring additional installation or configuration on the Windows machine.
Potential issues:
File paths: Relative paths used in the HTML might not resolve correctly on the Windows file system.
Permissions: Files generated on the Linux machine might have permissions incompatible with Windows, causing access issues.
Missing binaries or libraries: Script execution within the HTML might require specific Linux binaries or libraries unavailable on Windows.
Possible solutions:
Use Docker: Building your application (including the HTML) within a Docker container ensures a consistent and isolated environment across platforms.
Package dependencies: If avoiding Docker, ensure all dependencies your HTML relies on are available and compatible with the Windows environment.
Test and adapt: Thoroughly test your HTML on both Linux and Windows machines, making adjustments for platform-specific differences.
In summary, while theoretically possible, directly transferring an HTML file from Linux to Windows without Docker poses many challenges. Using Docker or carefully adapting your HTML and its dependencies for Windows are generally more reliable and efficient options.
@@RaghavPal This is really helpful Raghav. I will also use it to explain the concept to my 15 year old. Sharing of knowledge likes this as we know helps make careers and lives of many people. Thank you and best wishes!!
please put a video on docker-compose
Preethi
can find it in my Docker playlist.. can check here automationstepbystep.com/
docker build -t myapp (my question is in -t what -means and why should we give - before t )
Sandhya
The `-t` flag in the `docker build` command stands for **tag**. It is used to specify a name for the image that will be built. The tag is used to identify the image and to make it easier to manage.
The `-` before the `t` flag is required because it tells Docker that the following argument is a flag. Flags are used to modify the behavior of Docker commands.
Here is an example of how to use the `-t` flag to build an image:
```
docker build -t myapp .
```
This command will build an image from the current directory and tag it with the name `myapp`. The `.` at the end of the command tells Docker to build the image from the current directory.
Once the image has been built, it can be used to create containers.
Here is an example of how to create a container from the `myapp` image:
```
docker run -it myapp
```
This command will create a new container from the `myapp` image and start it in interactive mode.
The `-t` flag is a very useful tool for managing Docker images. It allows you to easily identify and manage your images.
Here are some of the benefits of using the `-t` flag:
* It makes it easier to identify and manage your images.
* It allows you to share your images with others by providing them with the tag name.
* It allows you to track the changes that have been made to your images.
* It allows you to create different versions of your images for different environments.
Overall, the `-t` flag is a valuable tool for anyone who uses Docker. It is a simple way to add more flexibility and control to your image management workflow.
when i am running "docker info " command it throwing '-bash: docker: command not found' statement how should i resolve this?
Aditya
The error message `-bash: docker: command not found` means that the `docker` command is not available in your current shell. This can happen if Docker is not installed on your system or if it is not in your `$PATH` environment variable.
To resolve this error, you need to make sure that Docker is installed and that it is in your `$PATH` environment variable.
Here are the steps on how to install Docker on Linux:
1. Open a terminal window.
2. Run the following command to install Docker:
```
sudo apt-get install docker.io
```
3. Once Docker is installed, you need to add it to your `$PATH` environment variable. You can do this by editing your `~/.bashrc` file.
```
export PATH=$PATH:$HOME/bin/docker
```
4. Save and close the `~/.bashrc` file.
5. Restart your shell.
Once you have completed these steps, you should be able to run the `docker info` command without any errors.
If you are still having trouble, you can refer to the Docker documentation for more information.
Here are some additional things you can try:
* Make sure that Docker is installed on your system.
* Check that the Docker daemon is running.
* Make sure that the `docker` command is in your `$PATH` environment variable.
* Try running the `docker info` command in a different shell.
* If you are still having trouble, you can post a question on the Docker forum or contact the Docker support team.
I see the welcome to the nginx page on the localhost web browser, (I tried all steps you had mentioned on a mac) and not the hello world page! what am I doing wrong? I even switched the browser from chrome to safari but I still see the same error!
Vartika
will need to check your setup and will need more details to troubleshoot
@@RaghavPal sure, is there a particular setup file that I should share?
I guess the issue may be the setup in aws security group, you will have to make ports open for communication, can check online on this
@@RaghavPal oh I am not using the aws server, I am just using my local mac to run this.
will need to check details then
Sir, I am not able to perform the last step. I am not able to launch the webpage via browser while copying the ip address from the aws and pasting it on browser.
Vaishnav
will need more details. What exactly is the error, do you see any message. Check the steps again and also try some online help. Let me know
How would i access your helloword from my pc? Or It's not possible. I am new to docker.
John
As of now the server is not running.. but if the ports are open.. it can be accessed using public ip and port of the running app
I'm getting trouble while build docker it is taking forever to build an image can you please fix this?
Unfortunately, troubleshooting a slow Docker image build requires more context about your specific scenario. To help you fix the issue, please provide additional information about the following:
*1. Dockerfile:*
* Share the content of your Dockerfile or a relevant snippet that takes the longest to build.
* Mention the specific instruction causing the delay.
*2. Build Context:*
* Describe the size and complexity of the files included in your build context.
* Mention any large dependencies being downloaded during the build.
*3. Build Logs:*
* Share the output of the `docker build` command, including any error messages or warnings.
* Look for specific lines indicating slow downloads or processing steps.
*4. System Resources:*
* Mention your available system resources, such as CPU cores, RAM, and disk space.
* Consider if resource limitations might contribute to the slow build.
*5. Build Environment:*
* Specify the version of Docker and the operating system you're using.
* Mention if you're using any specific features or plugins like multi-stage builds.
Once you provide this information, I can analyze the specific factors causing the slow build and offer targeted solutions.
Here are some additional tips for optimizing your Docker image build:
*Use multi-stage builds:* Separate your build process into stages to minimize the final image size.
*Cache layers:* Leverage Docker caching to avoid rebuilding frequently used layers.
*Minimize dependencies:* Only include necessary dependencies within your image.
*Use smaller base images:* Opt for smaller base images like Alpine Linux to reduce the initial image size.
*Optimize build scripts:* Analyze and optimize your build scripts for efficiency.
*Increase available resources:* If possible, allocate more CPU cores, RAM, or faster storage for smoother builds.
By applying these tips and providing the necessary details, I can effectively assist you in fixing the slow Docker image build issue.
the mechanics are great (how to do something step by step) but the practicality is missing; that is, if you could provide a real or small application to be containerized it would help a great deal.
I will work on this Linda
Thanks for the feedback
Hi sir when i am running using public ip got from ec2 i am geeting message " welcome to nginx , if you are seeing this message means nginx setuped successfully"
But i am.not getting the index.html file
Please reply
Shivam
Here are steps to address it:
1. Check Nginx Configuration:
Review /etc/nginx/nginx.conf: Ensure the server block for your website has the correct root directive pointing to the directory containing your index.html file.
Verify index Directive: Confirm the index directive includes index.html as a default file to serve.
2. Inspect File Permissions:
Check Read Permissions: Use ls -l /path/to/index.html to verify Nginx has read permissions for the file and its parent directories.
Adjust Permissions: If necessary, use chmod to grant appropriate permissions (e.g., chmod 644 /path/to/index.html).
3. Examine Server Logs:
Analyze Error Messages: Check Nginx error logs at /var/log/nginx/error.log for clues about configuration issues or file access problems.
4. Test File Existence:
Access Directly: Try accessing the index.html file directly using the full path in your browser to rule out file corruption or location issues.
5. Restart Nginx:
Reload Configuration: Use sudo service nginx reload or sudo systemctl reload nginx to apply any configuration changes.
6. Check Firewall Rules:
Allow HTTP Traffic: Ensure your EC2 instance's firewall rules allow inbound HTTP traffic on port 80 (or the port Nginx is listening on).
7. Consider SELinux:
Disable Temporarily: If using SELinux, temporarily disable it using sudo setenforce 0 to test if it's interfering. Re-enable with sudo setenforce 1 after troubleshooting.
8. Validate Directory Structure:
Confirm Structure: Ensure the index.html file is located in the directory specified by the root directive in your Nginx configuration.
Additional Tips:
Virtual Hosts: If using virtual hosts, ensure the correct virtual host configuration is active.
Custom Configuration: Review any custom Nginx configuration files for potential issues.
Troubleshooting Tools: Use tools like curl or wget to test accessing the file from the server itself
@@RaghavPal thanks for your support, will try this
I have tried the same in Azure and getting "The site cann't be reached' error. Any help appreciated.
Mohan
will need more details with your steps and logs
Failed to start docker.service: Unit docker.service not found. I'm getting this error, how to solve?
Sejal
The error message "Failed to start docker.service: Unit docker.service not found" indicates that your system cannot locate the Docker service unit file. This can happen for several reasons, so here are some steps you can take to troubleshoot and solve the issue:
1. Confirm Docker installation:
Verify that Docker is installed correctly on your system. You can check this by running the command docker ps in your terminal. If it returns an error message that Docker is not found, you need to install or reinstall Docker according to your operating system instructions.
2. Check service status:
Even if Docker is installed, the service might not be active. Run the command sudo systemctl status docker.service to check its status. If it shows "inactive" or "failed," you need to activate it.
3. Activate Docker service:
Use the command sudo systemctl start docker.service to activate the Docker service. Check the status again using sudo systemctl status docker.service to confirm it's running.
4. Verify unit file existence:
If the service activation fails, it's possible that the unit file is missing. Depending on your Docker installation method, the unit file location might differ.
For Debian/Ubuntu-based systems, the file should be located at /lib/systemd/system/docker.service.
For Red Hat/CentOS-based systems, the file should be located at /usr/lib/systemd/system/docker.service.
If you installed Docker using a different method, check its documentation for the specific location of the unit file.
5. Additional troubleshooting:
If the unit file is missing, it might indicate an incomplete or corrupted Docker installation. Try reinstalling Docker and double-check the installation process.
In some cases, system configurations or permission issues might prevent the service from running. Consult the Docker documentation for your operating system for more advanced troubleshooting tips or consider seeking help from your system administrator.
By following these steps and investigating the cause based on your specific system configuration, you should be able to resolve the "Unit docker.service not found" error and get your Docker service running again.
Hi Sir...
In Docker file, Many instructions/components may not change. i think only CMD and ENTRYPOINT varies in each and every Dockerfile.
My question to you sir....
Based upon a programming language, CMD and ENTRYPOINT may change. As a Non-It student and As a fresher, i have to know the complete flow of each and every application to write a Dockerfile. How i can achieve that and how i can write CMD and ENTRYPOINT fields in a Dockerfile for different programming languages ?
*I have seen a lot of videos, But i cannot get clarity about the applications like DOTNET, PYTHON etc.....
*So, i request you sir to upload a video about the workflow of different applications(programming/other) for DevOps engineers. It helps a lot for freshers and i think it will be also helpful for non-it background students as well ?
Harinath
You are correct that the CMD and ENTRYPOINT instructions are the most likely to change in a Dockerfile, depending on the programming language and the application.
The **CMD** instruction specifies the default command that will be executed when the container starts. The **ENTRYPOINT** instruction specifies the command that will always be executed when the container starts, even if it is overridden by the `CMD` instruction.
For example, the following Dockerfile for a Python application specifies the `python` command as the `CMD`:
```
FROM python:3.9
CMD python app.py
```
This means that when the container starts, the `python` command will be executed, and the `app.py` file will be passed as an argument.
The following Dockerfile for a .NET application specifies the `dotnet` command as the `ENTRYPOINT`:
```
FROM mcr.microsoft.com/dotnet/core/sdk:3.1
ENTRYPOINT dotnet myapp.dll
```
This means that when the container starts, the `dotnet` command will always be executed, and the `myapp.dll` file will be passed as an argument.
The `CMD` and `ENTRYPOINT` instructions can also be used to pass environment variables to the application. For example, the following Dockerfile for a Python application specifies the `PORT` environment variable:
```
FROM python:3.9
ENV PORT 8080
CMD python app.py
```
This means that when the container starts, the `PORT` environment variable will be set to `8080`.
The `CMD` and `ENTRYPOINT` instructions can be used to customize the behavior of the container. The specific commands and arguments that you use will depend on the programming language and the application.
I understand that you are a non-IT student and a fresher. It can be difficult to learn the workflow of different applications, especially if you are not familiar with the programming languages. However, there are a few resources that can help you.
One resource is the Docker documentation. The documentation has a section on writing Dockerfiles, and it also has examples of Dockerfiles for different programming languages.
Another resource is the Docker Hub. Docker Hub is a repository of Docker images, and it also has a community forum where you can ask questions and get help from other Docker users.
Finally, there are a number of online courses and tutorials that can teach you how to write Dockerfiles. A quick Google search will turn up many results.
I hope this helps! I am still under development, and I am not able to create videos yet. However, I can provide you with information and resources that can help you learn about Dockerfiles and the workflow of different applications.
@@RaghavPal Thanks a lot ❤SIR...Thanks for your valuable TIME and information. It helps me a lot SIR...
Where have you been all my life?
hope it was helpful
i dont understand the destination path of copy instruction , pls explain anyone
will need more details on this
Can u tell me how to write docker file using github url
Here is an example of a Dockerfile that uses a GitHub URL:
Dockerfile
FROM python:3.8
RUN git clone github.com/your-username/your-repo.git /app
WORKDIR /app
RUN pip install -r requirements.txt
CMD ["python", "app.py"]
This Dockerfile will:
* Pull the latest version of Python 3.8 from Docker Hub.
* Clone the GitHub repository your-username/your-repo into the /app directory.
* Change the working directory to /app.
* Install the dependencies listed in the requirements.txt file.
* Run the python app.py command.
To build the Docker image, you can run the following command:
Code snippet
docker build -t your-username/your-repo .
Once the image is built, you can run it with the following command:
Code snippet
docker run your-username/your-repo
This will start the Python application from the app.py file.
Here are some additional things to keep in mind:
* The FROM instruction specifies the base image for the Dockerfile.
* The RUN instructions execute commands in the Dockerfile.
* The WORKDIR instruction sets the working directory for the Dockerfile.
* The CMD instruction specifies the command that will be executed when the Docker image is run.
I hope this helps
Not sure on this
unable to run docker on aws What is the command line to run docker on Windows
Pavan
The command line to run Docker on Windows is:
```
docker run
```
For example, to run the Ubuntu image, you would use the following command:
```
docker run ubuntu
```
This command will create a new container from the Ubuntu image and start it. You can then interact with the container using the `docker` command.
Here are some other commands that you can use to run Docker on Windows:
* `docker images`: List all of the images that are available on your computer.
* `docker ps`: List all of the running containers.
* `docker stop `: Stop a running container.
* `docker start `: Start a stopped container.
* `docker remove `: Remove a container.
If you are unable to run Docker on AWS, it is possible that you do not have the Docker daemon installed. You can install the Docker daemon using the following command:
```
sudo apt install docker.io
```
Once the Docker daemon is installed, you can start it using the following command:
```
sudo service docker start
```
You can then try running the `docker run` command again
Thanks for information I clearly understanded now
I tried to build the image it shows access denied fir nginix
Ahkansha
Check this forums.docker.com/t/issue-403-forbidden-13-permission-denied-nginx/121658
Show docker multistage build
will plan a lecture on this Sheethu
Pull access denied for nginix how to do that ???😢😢😢😢
Hi Shamim
The error message "pull access denied for nginx" means that you are not authorized to pull the nginx image from Docker Hub. This can happen for a few reasons:
* You may not have logged in to Docker Hub.
* You may not have the correct permissions to pull the image.
* The image may be private and you do not have access to it.
To fix the error message "pull access denied for nginx", you need to log in to Docker Hub and make sure that you have the correct permissions to pull the image. If the image is private, you will need to be granted access by the owner of the image.
Here are the steps on how to log in to Docker Hub:
1. Open a terminal window.
2. Run the following command:
```
docker login
```
3. Enter your Docker Hub username and password.
Once you have logged in to Docker Hub, you can check the permissions for the nginx image by running the following command:
```
docker image inspect nginx
```
The output of this command will show you the permissions for the image. If the image is private, you will see a "pull" section that shows the usernames that have access to the image.
If you do not have access to the nginx image, you can contact the owner of the image and request access.
Here are the steps on how to request access to a private image:
1. Go to the Docker Hub page for the image.
2. Click on the "Permissions" tab.
3. Click on the "Request Access" button.
4. Enter your Docker Hub username and a message explaining why you need access to the image.
The owner of the image will be notified of your request and they can decide whether or not to grant you access.
Once you have been granted access to the nginx image, you will be able to pull the image without any errors.
I m runnung local host and not able to find hello world😢
will need to check the details. Can try some online examples
How if docker is not running
Durga
Did not get you.. we are doing it with Docker.. what other ways are you trying or suggesting here
@@RaghavPal when you are checking if docker is running or not ,you gave one command know,that command is not working for me,then docker is not working
@@RaghavPal@9:42 min
okay, that mostly be due to docker is not installed or setup on your system.. check the steps for docker setup.. Can refer Docker Playlist - th-cam.com/play/PLhW3qG5bs-L99pQsZ74f-LC-tOEsBp2rK.html
@@RaghavPal i installed successfully sir but don't know y
Can anyone help me
Aditya
please tell me your ques
@@RaghavPal when i am running "docker info " command it throwing '-bash: docker: command not found' statement how should i resolve this?
At 9:40 after cat docker , when I am running docker info its showing '-bash: docker: command not found'
The error message `-bash: docker: command not found` means that the `docker` command is not available in your current shell. This can happen if Docker is not installed on your system or if it is not in your `$PATH` environment variable.
To resolve this error, you need to make sure that Docker is installed and that it is in your `$PATH` environment variable.
Here are the steps on how to install Docker on macOS:
1. Open a terminal window.
2. Run the following command to install Docker:
```
brew install docker
```
3. Once Docker is installed, you need to add it to your `$PATH` environment variable. You can do this by editing your `~/.bash_profile` file.
```
export PATH=$PATH:$HOME/opt/homebrew/bin
```
4. Save and close the `~/.bash_profile` file.
5. Restart your shell.
Once you have completed these steps, you should be able to run the `docker info` command without any errors.
If you are still having trouble, you can refer to the Docker documentation for more information.
@@RaghavPal I have docker added to $PATH and also the docker is installed with the latest version but still its showing the same also I am working on windows not macOS
I have a doubt on COPY command which we are using in dockerfile.
In your scenario you used "COPY index.html /usr/share/nginx/html
So here index.html is source and /usr is destination right?
So can we use mention anything in the destination location like /app/ ?
First of all why are we using copy command?
We are going to paste the index.html code in the nginx server
You used COPY index.html but what's is the purpose of destination location?
Can you please explain this?
Sneha
You're correct in understanding the basic usage of the `COPY` command in Dockerfile. Here's a breakdown of your questions:
*1. Source and Destination:*
* Yes, in your example, `index.html` is the source file located in your current directory (context of the Dockerfile).
* `/usr/share/nginx/html` is the destination location within the Docker container.
* You can use any valid path as the destination, including `/app/` or any other directory you create within the container.
*2. Purpose of COPY command:*
The `COPY` command is used to copy files from your local machine into the Docker image being built. This allows you to include your application code, configuration files, static assets, and other necessary files within the container.
*3. Destination location:*
The destination location specifies where the copied files will be placed inside the container. This helps you organize your files and ensure they are accessible to the application running within the container. In your example, `/usr/share/nginx/html` is the default location for the Nginx web server, so placing `index.html` there makes it accessible to Nginx.
*4. COPY command and pasting code:*
While the `COPY` command copies files, it doesn't "paste" code in the sense of directly editing the code within the container. It simply copies the file itself, allowing you to access its content. You might need to perform additional configuration steps depending on your application's requirements, such as linking the file to a specific location within your application.
*In summary:*
The `COPY` command is crucial for including necessary files within your Docker image. You can specify both the source file on your local machine and the destination location within the container. This allows you to build an image containing all the necessary components for your application to run successfully.
@@RaghavPal so we can give whatever location we want right in the destination.
We can't set the location in the docker manually and through the command only we can set the location in the docker right?
Sneha
Yes, you're correct. You can provide any valid location you want in the destination path of the `COPY` command in the Dockerfile. This path will determine where the copied file resides within the Docker container.
While you can manually create directories within the container using commands like `mkdir`, the `COPY` command offers a more convenient way to ensure the files are placed in the correct location during the image build process. This approach helps maintain consistency and avoids the need to remember specific commands for creating directories later.
Here are some additional points to consider:
The Dockerfile uses a layered approach, meaning each instruction builds upon the previous one. Therefore, if you specify a directory in the destination path that doesn't exist yet, the `COPY` command will automatically create it.
You can copy multiple files and directories using wildcards or globbing patterns within the source path of the `COPY` command.
While you can technically set the location manually within the container after it's built, using `COPY` is generally considered best practice for ensuring reproducibility and consistency in your Docker image build process.
In summary, the `COPY` command provides a powerful and convenient way to place files in specific locations within your Docker container during the image build process. Using this approach promotes maintainability and avoids the need for additional manual manipulations within the container.
Why did u use the path /use/share/nginx/html ,,is that any specific path,where did we got to know that path
Jayarani
Here's why the path /usr/share/nginx/html is commonly used, and where the knowledge of this path originates:
1. Default Document Root:
- NGINX Configuration: This path is typically set as the default "document root" in NGINX's configuration files.
- Meaning: It's the primary directory where NGINX looks for files to serve when a website is requested.
2. Filesystem Hierarchy Standard (FHS):
- Convention: The path adheres to the FHS, a common directory structure for Linux-based systems.
- Purpose: FHS promotes consistency and predictability in file locations.
3. Path Breakdown:
- /usr: Contains shared, read-only user data and applications.
- /share: Stores architecture-independent data for applications.
- /nginx: Holds NGINX-specific files and directories.
- /html: The designated document root directory for web content.
4. Knowledge Source:
- NGINX Documentation: The path is explicitly mentioned in the official NGINX documentation as the default document root.
- Distribution Documentation: Linux distributions often document this path in their NGINX installation guides.
- Community Knowledge: It's widely shared within online communities and forums discussing NGINX.
Key Points:
- Configurable: While it's the default, you can change the document root to another directory in NGINX's configuration.
- Distribution-Specific: Some Linux distributions might have slightly different default paths.
- Check Configuration: If unsure, consult your specific NGINX configuration to verify the document root's location.
Understanding this path's significance and origins aids in effectively managing NGINX web servers and knowing where to place web content for serving.
@@RaghavPal Thanku for ur inputs
I'm getting /docker-entrypoint.sh:47:exec:.: Permission denied
Could you please help me on this? I don't know why I'm getting this when I'm running the image
Sneha
The error message "docker-entrypoint.sh:47:exec:.: Permission denied" indicates that the docker-entrypoint.sh script does not have executable permissions. This means that the container cannot run the script when it starts up.
To fix this error, you can change the permissions of the docker-entrypoint.sh script to allow execution. You can do this by running the following command from your host machine:
```bash
chmod +x docker-entrypoint.sh
```
This will add the executable permission to the script, and the container will be able to run it when it starts up.
Here is an explanation of the command:
* `chmod`: This is the chmod command, which changes the permissions of files and directories.
* `+x`: This is the flag that tells chmod to add the executable permission to the file.
* `docker-entrypoint.sh`: This is the name of the file that you want to change the permissions of.
Once you have run the command, you should be able to start the container without getting the error message.
@@RaghavPal Cannot access 'docker-entrypoint.sh': No such file or directory.
It's saying no such file or directory when I use chmod command to change it's permission
The error message "Cannot access 'docker-entrypoint.sh': No such file or directory" indicates that the specified file, docker-entrypoint.sh, does not exist in the current working directory or in the location specified by the environment variable PATH.
This can happen for a couple of reasons:
1. **The file does not exist:** If you extracted the image to a specific location, ensure you're navigating to that directory before running the chmod command.
2. **The image is corrupted:** If you downloaded the image from a registry or repository, it's possible the image file is corrupt or incomplete. Try downloading the image again from a different source.
To check if the file exists, try running the following command:
```bash
ls -la
```
This will list the contents of the current directory, including hidden files. If docker-entrypoint.sh is present, it should be listed in the output.
If the file doesn't exist, you can try specifying the full path to the file when running the chmod command:
```bash
chmod +x /path/to/docker-entrypoint.sh
```
Replace '/path/to/docker-entrypoint.sh' with the actual path to the file.
If the file still doesn't exist or the image is corrupted, you'll need to redownload the image or extract it to a different location.
@@RaghavPalI'm not able to find the docker-entrypoint.sh even after using ls-la.
I don't think my image got corrupted
will need to check more on this online
An acronym for some of the most commonly used instructions in a Dockerfile is A WELSH CAFE COURSE.
A - ADD
W - WORKDIR
E - EXPOSE
L - LABEL
S - SHELL
H - HEALTHCHECK
C - CMD
A - ARG
F - FROM
E - ENV
C - COPY
O - ONBUILD
U - USER
R - RUN
S - STOPSIGNAL
E - ENTRYPOINT
Thanks for adding
Thank you!
You're welcome!