DEV Community: Shashank Katte

Docker Cheatsheet for Web Devs

Shashank Katte — Thu, 01 Jul 2021 16:06:43 +0000

As a web-dev in the microservices era you will encounter Docker sooner than later. It's always good to have the essential commands at arm's reach. Following is a list of Essential Docker commands that have helped me on a daily basis, hope this helps yo too. Happy Hacking!

Docker Commands

Docker run command

docker run <image-name>

example
docker run hello-world

To add a override command

docker run <image-name> <default command override>

example

docker run busybox ls

List all the running containers

Docker ps command specifically shows running containers

docker ps

Show all container ever run on machine

docker ps --all

Docker ps is also used to get the ID of coantainer

docker run = docker create + docker start

when we create container we just prep it with say file sysytem etc
When we run the container then we provide the default command that runs the program

docker create hello-world

now we use the id to start

docker start -a 3c8a5bb0fe7153955d1261054e5b4c99f757920f7760fa7c07803cdbee4b36c1

-a argument watches for any output and prints it on terminal

To re-run an exitied container

first we get the conatiner of ID with ps command

docker ps --all

Then use the id with start command

docker start -a 1285b5630516

When we re-run / restart a container we cannot replace the default command, it automatically takes the default command on re-run with commond it was created with.

Removing stopped containers

docker system prune

Docker logs command

Docker logs command shows all the output of con tainer when it had been running

docker logs 73e564097bd5e6689c2bc5687c038dca99ec77d8716f7ff9eeab9434d422bb8d

Stopping a running container

docker stop <container-id>

This sends a SIGTERM signal allowing container to shut down in some time usually 10s, after that it issues Docker kill anyway

docker kill <container-id>

This command issues a SIGKILL that immediately stops the container

Docker stop is better way to stop*

Executing commands in running containers

docker exec -it <container-id> <command>

exec command allows us to type extra commands
it flag helps us to enter text and send it to container

The it flag

its a -i and -t
i attaches our terminal to STDIN
t flag makes sure that it shows the output formatted on terminal, like auto complete you see with redis-cli

How to get shell access in docker container

sh is command processor like bash, zsh etc

docker exec -it <container-id> sh

if ctrl + c doesnt help you exit use ctrl+d or just type exit

starting container with a shell

docker run -it <container-name> sh

Creating a Docker image

Flow to Creating a DockerFile

specify base image
Run some commands to install additional programs
specify command to run on container startup

Sample docker file to create redis image

Create a file named Dockerfile no extension just Dockerfile

# Use an existing docker image as base 
FROM alpine


# Download and install a dependency
RUN apk add --update redis

# Tell the image what to do when it starts as a container
CMD ["redis-server"]

use the docker build command to build image

docker build .

Run the image as usual

Writing a docker file == say, given a computer with no OS and being asked to install chrome

Tagging an image

docker build -t <docker-hub -id>/<project>:<version> . Dont forget the dot at the end.

to run the image

docker run <docker-hub -id>/<project>

this automatically takes the latest version.

Technically, the version number at the end is the actual tag here

Manual image generation with docker commit

docker commit -c 'CMD ["<command>"]' <container id>

Copy build files

COPY <relative local file system> <relative dest>

Port forwarding

docker run -p <portno> : <container-port-no> <image-id>

Specifying a working directory

WORKDIR /usr/app

Any following commands will be executed relative to working dir

Open source MERN survey APP for you to Learn and contribute

Shashank Katte — Fri, 09 Apr 2021 21:02:18 +0000

Github link here

Feedbackr is an Opensource and free survey app. 📝. Use it as a starter app to build your own custom feedback collection App or use it as your reference to explore a production ready MERN App.

If you are exploring MERN stack, this app will show you:

how to use React and Redux
Routing with React routing
Using reusable Redux Forms
Payments with Stripe
Google OAuth Authentication with Passport.js
Persisting data into MongoDB and using Mongoose
Using webhooks
Sending Automated Emails
API key handling techniques and Deployment strategy with configs to Heroku

This is a very good App for you to practice your MERN Skills and contribute to opensource. See you there!

Github link here

The App is based off of learnings from great teachers like Stephen Grider, Brad traversy, Max - Academind, Freecodecamp and many more.

Open-source TypeScript Tutorial

Shashank Katte — Mon, 15 Mar 2021 19:30:37 +0000

Here's a simple, Open-source repo to learn and practice TypeScript.

Instead of creating a long article on all the basics of TypeScript, I have created a GitHub Repo with the combination of README and source files to help us learn and refresh our TypeScript skills right in our code editor.

It's a growing open-source repo, where you can collaborate and enhance it with your knowledge, practice code snippets, sample apps and best practices.

Beginners, experts and curious minds all are welcome.

21 Lessons from Building Clones On youtube

Shashank Katte — Mon, 01 Mar 2021 21:42:12 +0000

Learning a new skill online is fun and free, but how do you make that learning permanent? Here are the lessons I have learned taking the journey myself.

I am eager to know yours :)

Part 1: Introduction to Cloud Computing with AWS

Shashank Katte — Mon, 22 Feb 2021 14:23:22 +0000

Cloud computing is an ocean and finding the right learning resources in a single place is a challenge.

I'm creating a series of Human understandable short articles on AWS from my own learnings over the years. - Cloud Fundamentals with AWS.

I hope this saves you time and helps you get from beginner to expert on AWS.

Here is Part 1: Introduction to Cloud Computing

Next posts on Cloud servers and Storage coming soon.

21 Lessons Learned from Building Clones On youtube

Shashank Katte — Thu, 11 Feb 2021 14:22:50 +0000

Learning to code Online is fun, free and exciting. But just binging on Videos building Tinder clones won't cut it. How do you solidify your learning? It takes strategy and focus.

Here are 21 lessons I learned my self going through online learning.

Getting along with Git & Github

Shashank Katte — Mon, 08 Feb 2021 19:07:53 +0000

A no non-sense reference for developers by a developer. Read here

How agile principles of ‘done’ can help you as a Software Developer

Shashank Katte — Sun, 07 Feb 2021 14:28:56 +0000

Learn how having a definition of done can protect you from unwanted distractions. Read more on how I've used it myself

7 Javascript Concepts to Master Before Any Framework / Library

Shashank Katte — Fri, 05 Feb 2021 16:37:35 +0000

These are the 7 concepts I feel are most important to understand and learn any new JS framework or library.Read the full article here

Shell Commands You Should Have Memorized Yesterday

Shashank Katte — Thu, 04 Feb 2021 14:11:54 +0000

Master the Terminal to be a productive developer

Photo by Louis Hansel @shotsoflouis on Unsplash

Being a developer means spending an awful lot of time in the terminal, especially Linux based terminal. You may fear this minimal dark text window, but it is your most potent ally to be a productive developer.

Terminals (a.k.a Console a.k.a command prompt) can be found everywhere. You find them integrated into your code editors like Visual Studio code or as a CLI (command line interface) to services like GitHub or AWS.

Being able to fire commands at will in the terminal saves you more time and energy than dragging your mouse pointer around clicking away at the GUI. Interestingly it’s not all that daunting to get started.

Let's look at the must-know commands…

1. Get to know where you are with “pwd”

The pwd command stands for the present working directory. *It tells you exactly which folder/directory you are in the file system. Think of this as your — *find my location service on google maps. Here’s how to use it: just type pwd at the cursor in the terminal, hit return and it outputs the path to your current directory.

$ pwd

2. Listing files and directories with “ls”

ls is a very powerful command that lists all the contents of a directory. You can use different flags along with it to choose what information is shown.

When you use it without any options, it displays the names of all the unhidden files and directories in the current directory you are in.

$ ls

Adding the -l flag along with ls will list all the unhidden contents of your current directory in a tabular format with more details

$ ls -l

Now, if we want to display all the hidden files and directories we use the -a flag. If we use it along with -l flag it lists all the contents including hidden ones in a nice tabular format

I highly recommend that you use this format of the ls command, to list out all the contents of directories.

$ls -al

In Linux/mac hidden files and directory names start with . , for example .my-secret-directory is a hidden directory.

3. Change directories with “cd”

cd stands for change directory. As you might have already guessed it helps us move around directories. Hitch a ride!

When you use cd without any flags, it takes you to your home directory/root directory. For example, if I try this command on my mac it will take me to my home directory /Users/shashank

$ cd

To get into a particular directory you use cd followed by the name of the directory

$ cd my-directory

you can also do multiple jumps per se and get into a directory nested into another directory (subdirectory) using the path. For example, if I want to jump into my projects folder I would do this

$ cd shashank/projects

4. Understand the dot “.” and double dots “..”

The single dot . is an alias for the current directory and the double dots .. is an alias for the parent directory.

So if you do a $ cd . You will still stay in the current directory. However, the single dot alias is much useful with other commands like open

$ open .

This launches your default file explorer at the current directory. If you are on mac this launces the finder displaying contents of the current directory.

now if you use

$ cd ..

This will take you one level higher or to the parent directory of your current directory.

Yes the alias for current and parent directory . and .. are also hidden. You will see them listed when you use ls with -a flag

5. Create Directories with “mkdir”

mkdir stands for make directory. To create a directory use mkdir with the directory name

$ mkdir my-new-directory

You can also use the long path to create directories provided the path until the new directory exists. For example, you can create my-new directroy like so:

$ mkdir /users/shashank/my-new-directory

This will work provided the directory structure /users/shashank already exists.

6. Crete a new file with “touch”

touch lets you quickly create an empty file or multiple files. This command is very useful when you need to create files without any content to test out logs etc. to use it you use touch followed by the filename(s) with extension.

$ touch log.txt dump.csv

7. Add content to file with “>” and “>>”

lets you overwrite and push content into a file. For example, you can push the contents from file1 to file2. The contents of file2 will be overwritten if it already has any content

$ file1 > file2

However, if you want to append content to an existing file without overwriting use >>

$ file1 >> file2

8. View the file contents with “cat”

The quickest way to display file contents on the terminal is to use the cat command. Similar to touch you can provide multiple file names.

$ cat file1 file2

9. Rename or move with “mv”

mv is used to rename files/directories or move files/directories from one place to another

To move a file

$ mv file1 my-directory

To rename a directory or file, provide the existing file/directory name followed by a new file name/directory name.

$ file1 newfile

If the second parameter is a new folder, the mv command moves the file/directory in the first parameter into the folder in the second parameter. Otherwise, it will rename the file.

10. Delete files and folders with “rm” and “rmdir”

You can delete a file using rm command.

$ rm filename

If the file is write-protected, you will be prompted for confirmation before deleting it. If it's not protected the command goes ahead to delete the file

To delete an empty folder use the rmdir command

$ rmdir my-directory

*Danger zone: *To delete a folder that contains files without any prompt use the rm command with flags r and f

$ rm -rf my-directory

11. Use the power of wildcards

Wildcards (also referred to as meta characters) are symbols or special characters that represent other characters. You can use them with any command like ls or rm to list or remove files matching given criteria.

An asterisk (*) – matches one or more occurrences of any character, including no character.
Question mark (?) – represents or matches a single occurrence of any character.
Bracketed characters ([ ]) – matches any occurrence of character enclosed in the square brackets. It is possible to use different types of characters (alphanumeric characters): numbers, letters, other special characters, etc.

Here we list all files with a .txt extension

$ ls -al *.txt

The following example matches all files with names beginning with l followed by any single character and ending with st.sh (which is the suffix).

$ ls l?st.sh

and below we match all files with names starting with l followed by any of the characters in the square bracket but ending with st.sh.

$ ls l[abdcio]st.sh

Caution: Be extra careful while using wildcards with rm or rmdir. It can prove disastrous

10. Clean up the terminal window with “clear”

With all the commands and inputs the terminal gets cluttered pretty fast. clear does what it says; it clears up the screen and takes your cursor right to the top so that you have a fresh clean area to fire more commands!

$ clear

All is not lost when you use the clear command, If you want to look back at the previous commands and outputs, just scroll up and it’s right there.

11. Use the “man” command to list a manual for any command

Use man the command to print the complete manual of any command that you can run in the terminal. It gives details on usage options, flags, error codes, etc. When in doubt man it!

Here man command will print the entire manual for ls command

$ man ls

Bonus: Understand the power of TAB autocomplete and Arrow keys history

These are not commands but short-cuts to reduce your typing in the terminal.

Use the TAB key for autocompletion when you are typing file or directory names. You can type a single character and hit TAB. You can cycle through all the options that start with the character

Also, you can cycle through the history of recently used commands using the up-Arrow and/or Down- arrow keys.

Where to go from here

We have covered the bare minimum commands here, however, they are enough to get you going. As you start using the terminal more often and dip your hands into various CLIs you will pick up the commands essential in your context. I encourage you to explore the linux.org documentation for more commands.

Thanks for reading and Happy hacking.

This post was first published on my Medium profile