Debug School: Joy

Git assignment- Day 4

Joy — Fri, 18 Nov 2022 07:22:05 +0000

git config
Usage: git config -global user.name “[name]”
Usage: git config -global user.email “[email address]”
This command sets the author name and email address respectively to be used with commits.

git clone
Usage: git clone [url]
This command is used to obtain a repository from an existing URL.

git add
Usage: git add [file]
This command adds one or more files to the staging area.

git commit
Usage: git commit -m “message”
This command stores the file permanently in the version history.

git status
shows the current status of the repo. Tracked or untracked files.

git log
shows all the commit history.

git diff
git diff [branch/commit] [branch/commit]
This command shows the differences between the two branches/commits mentioned.

git rm
Usage: git rm [file]
This command deletes the file from your working directory and stages the deletion.

git revert
puts the commit id below the specified commit id on top.

git branch
Usage: git branch [branch name]
This command creates a new branch.

git checkout
goes to the specified branch.

git merge
Usage: git merge [branch name]
This command merges the specified branch’s history into the current branch. we can also pick the merge policy.

git pull
This command does fetch + merge.

git push
pushes the local repo commits to remote repo and to specified branch.

Docker Assignment 1-Day 3

Joy — Wed, 16 Nov 2022 05:12:13 +0000

How can we store container data in memory using docker volume?
We can use the tempfs as mount type.

docker run --mount type=tmpfs,dst=/tmp command creates a blank tmpfs device and attaches it to the new container’s /tmp file tree. Any files created under this file tree will be in memory storage rather than on disk. Using the --tmpfs flag is also doing the same thing but the destination is not configurable.

Docker Assignment 3- Day 2

Joy — Tue, 15 Nov 2022 06:34:00 +0000

What is a docker image?

Docker image is a collection of repositories.
There could be multiple layers in a docker image.
While pulling a docker image we pull the top layer and along with it all the layers linked to it are also pulled.
The layers are linked in a parent child fashion, where the second top layer is the parent of top layer and so on.
The last layer is the root file system. Each layer is its own file system.
When the container is running, all the layers are merged and mounted to the container.
When the container is stopped, the merged mount is gone.
The changes in the file system of each layer is maintained in a separate diff folder and when the container starts the changes are also merged in the mount.

Docker Assignment 1- Day 2

Joy — Tue, 15 Nov 2022 04:59:53 +0000

What is the use of docker update command?
docker update is used to update configs of one or more containers. We can set cpu resources, memory limitations, restart policy etc of containers using this command.

What is the use of Docker wait?
Docker wait container blocks until the container is exited and returns the exit code.

Docker Assignment 2- Day 1

Joy — Mon, 14 Nov 2022 10:06:00 +0000

what is the difference between docker pause and docker unpause?

Docker pause suspends the processes running inside the container and does that by freezer cgroup. In the traditional method of suspending a process in Linux, SIGSTOP is used but it is observable by the process that it is being suspended. But docker pause uses freezer cgroup, so the process is unable to capture that it is being suspended.

The docker unpause command unsuspends the processes inside the specified container. The freezer cgroup checkpoints the images of the tasks before suspending them, so while unsuspending they can resume. The checkpointed tasks can also be migrated before restarting.

What is the diff between docker stop and docker kill?

Docker Stop will send SIGTERM signal to the main process and after allowing sometime to gracefully stop the process, the will send SIGKILL. So the process gets some time to close gracefully.

Docker kill will send the SIGKILL immediately to the main process inside the container. The default signal can also be changed using --signal flag.

Docker Assignment

Joy — Mon, 14 Nov 2022 07:23:50 +0000

What is Docker?
It is a container management tool.

Why Docker?
To setup application faster, without OS cost.

What is Container?

Container is a software unit with its own network, process, root filesystem etc. resources, which can be used to set up applications.

Docker workflow and how container is created?

The docker cli from docker demon will talk to docker client and then docker client will pull the images from registry. Once the images are pulled we can run the images using the commands from docker client.