Forem: Bibhu Sunder

DOCKER SWARM

Bibhu Sunder — Fri, 08 Jul 2022 09:14:26 +0000

WHAT IS DOCKER?
Docker is a tool which is used to automate the deployment of applications in lightweight containers so that applications can work efficiently in different environments.
Point to be noted- Container is a software package that consists of all the dependencies required to run an application.

Advantages of docker-

Multiple containers run on the same hardware
Maintains isolated applications
High productivity
Quick and easy configuration

WHAT IS DOCKER SWARM?
Docker swarm is a service which allows user to create and manage a cluster of Docker nodes and schedule containers.

Each node of a Docker Swarm is a Docker daemon and all Docker daemons interact using the Docker API.

Here, services can be deployed and accessed by nodes of same cluster.

Now lets see how we can set-up Docker Swarm using AWS EC2 instances.

First of all create at least 4 EC2 instances. One of them will be used as master node and other three will be used as worker node.
Allow ssh, http and https in the inbound rules of the security group.

Then we need to install docker in all the 4 instances using the command "yum install docker* -y"

Once installation is completed we need to start docker by the following commands

systemctl start docker
systemctl enable docker

Now we need to configure the master node as the master node. the command for that is

docker swarm init

To convert all the other nodes into worker node we need to copy the highlighted area given in the above picture and past that command in all other nodes which we want to make as worker node.

To check all the available docker nodes we can write

docker node ls

Then we need to create a docker file where we will write the script to launch an image and provide the web page which we want to launch.
To create the docker file we need to write "vi Dockerfile"

Now we need to built an image.

We need to perform the above two steps in all the worker nodes too.

Then we need to create service.
-docker service create --name app-server -p 80:80 appimage:1

It will create a container in any one node but if we hit the public IP address of any of the instance we can see the web page is running regardless in which instance the container is.

It is very easy to increase or decrease the numbers of services in docker, we can simply do it by the command given below.

We can also view our containers using a docker visualizer, which is a graphical representation of all the containers and instances.
To set-up visualizer we need to run the given command.

docker service create --name=viz --publish=8080:8080/tcp --constraint=node.role==manager --mount=type=bind,src=/var/run/docker.sock,dst=/var/run/docker.sock dockersamples/visualizer

Now if you hit the public ip of the master node mapped with port 8080 you can see the Docker visualizer.

This was the whole process of how to set-up docker swarm.

APPLICATION MIGRATION IN AWS

Bibhu Sunder — Sun, 03 Apr 2022 11:37:51 +0000

Application migration is the process of moving software applications from one computing environment to another. This can include migrating applications from one data center to another, such as from a public to a private cloud, or from a company's on-premises server to a cloud provider's environment.

Here we will see how we can migrate our server form one AWS account in one region to another AWS account in some other region or in same region.

This is the server(source server) of Singapore region which we are going to migrate to Mumbai region of another AWS account.

This is the sample web site(downloaded from free-css.com) which is hosted form the source server.

Now in your destination AWS account and go to "AWS Application Migration Service" and click on "Get started".

Then click on "Add servers"

First we need to select our application server type(i.e. Linux)
Then click on create IAM user

Once you created an IAM user by the name "mgn-agent-installer" then copy and past the Access key ID and Secret access key
in their respective place.

Now copy the " Download the installer using this command:" by clicking on the copy button and past it in the Xshell (paste in the source server).

Repeat the same process for step 5( Copy and input the command below into the command line on your source server)

Then go back to the "Source servers" and click on your "Source server name"

Then go to "Launch settings and click on "modify"(EC2 Launch Template)

Now keep things same as shown in the pictures below

The instance type must be same as of your source server, then you need to give a key pair for your destination instance and you also need to specify the subnet inside which you want to deploy the server.

Now assign a security group(allow http, https, ssh)

Then click on "Create template version"

Go to "Launch templates" select the template click on "Action" and click on "Set default version".

Now again go to your source server and then click on launch setting and then click on edit (General launch settings) and make "Instance type right sizing" OFF

Now wait until the "lifecycle" becomes "ready for testing"

After it becomes ready for testing. Go to source servers and "launch test instances"

If you go to ec2 instances you can see that automatically some instances are created and terminated for testing purpose

wait until the instance(1.compute.internal) is created and status is checked(2/2 check pass)
Associate an elastic IP to it so that we can test weather the web page is successfully transferred to the server or not

Now if you past the elastic IP in the browser you can see webpage is up and running.

So, our testing process is completed.
The next step is to go to the source servers and make the server "ready for cutover"

Then launch cutover instance

Once this instance becomes ready associate the elastic IP to it.

The above server is the final migrated server.

Now go to Application migration and finalize cutover

Then mark as archived

This was the complete process of application migration.
Now you can delete and terminate all the other things except (compute.internal) this server and the allocated elastic IP to it.

Increase or Decrease the size of an EBS volume in AWS.

Bibhu Sunder — Thu, 20 Jan 2022 16:59:02 +0000

Suppose you have created an EC2 instance and attached an EBS volume to it.

Lets first check how can we increase the storage capacity of the EBS volume.

To do so go to the volume section, select the volume whose storage capacity you want to increase then click on action and then click on modify volume.

Now you can increase the storage size to your desired size.
(My present size is 15Gb I am going to convert it to 20 Gb)

PLEASE NOTE THAT YOU CAN ONLY INCREASE THE SIZE HERE,YOU CAN NOT DECREASE THE STORAGE SIZE FROM HERE.

Now after changing the size click on modify and then again click on modify.

Now wait until the volume to optimize 100%, you can check it by going to the volume section

Once its optimized 100% you can go to Xshell and type lsblk. You can see that the storage size have increased to your desired size.

But if you type df -h then you will see that the size of the external storage is still 15gb.

This is because we have not resized the size of volume in the instance end. So, we can resize by typing a command in the Xshell.
Just write resize2fs /dev/xvdf and then if you type df -h then you will find that the size of your volume is increased.

This is how you can increase the size of your EBS volume.

Procedure to decrease the size

The process to decrease the size of the EBS volume is totally different form that of increasing the size. But this is also quite easy.

Suppose your current volume size is 20Gb and you want to convert it to 10Gb then you just need to go to the volume section and create a EBS volume of 10Gb at the same Availability Zone as of your EC2 instance.

Now give it a name tag(its optional) then click on create volume.

Then select the newly created volume and click on action and then press on attach volume.

Then select the instance and then press attach volume.

Now do the same old process of formatting and mounting the new volume in the instance.

Now we just need to sync all the data from the previous external storage to the new reduced external storage. The command to do so is rsync -aHAXxSP /ext_vol /red_ext_vol/

Now all the data from the previous External storage is transferred to the new external storage, so now we need to unmount the previous external storage. The command to do so is** umount /dev/xvdf**.After doing that go the volume section and select external volume and click on detach volume.

Now once its status become available just select the volume again click on action and click on delete volume.

This is the whole process by which we can reduce the size of an EBS volume.