Wednesday, May 3, 2017

Attaching an EBS Disk to a Linux Instance

In the previous blog, we looked the sequence of steps to create a Linux instance and log into it. In this blog, we will create a new hard disk (actually an EBS) and attach it to the Linux instance. I am going with the assumption that the EC2 instance has already been created.

1. Goto the EC2 management console and click on the Volumes in the left pane. And then click on `Create Volume`. Change the volume size to 1GB and click on Create.

2. It takes a couple of seconds, but there will be two EBS volumes. An 8 GB volume (in-use) which was automatically created at the the time EC2 creation. Another 1 GB volume (attached) which was created in the above step.

3. Select the 1 GB volume. Click on Actions and then Attach Volume. We have created a Linux EC2 instance and an EBS volume, now we need to attach these two.

4. Move the cursor to the instance box and select the EC2 instance to which the EBS has to be attached and then click Attach. The state of the 1GB instance should change from available to in-use.

5. Get the ip address of the EC2 instance and login to it using Putty as mentioned here.

6. Change to root (sudo su) and get the list of the partition tables (fdisk -l). The commands are mentioned in the parentheses. Note that the device name is /dev/xvdf from the below commands. It may vary, so the previous mentioned commands have to be run.

7. Build the Linux filesystem (mkfs /dev/xvdf), create a folder (mkdir /mnt/disk100) and finally mount the file system (mount /dev/xvdf /mnt/disk100). The commands are mentioned in the parentheses. Note that, I have chosen to create disk100 folder, you can replace with any other folder name.

Now the device has been mounted to /mnt/disk100 folder, the data in this folder will be written to the 1 GB EBS volume which we have created in one of the previous step. Even after stopping the EC2 instance, the data will be still there in the EBS instance. This EBS can be attached to another EC2 instance also.

Note that in the case of AWS, an EBS volume cannot be attached to multiple EC2 instances. But, the same thing can be done in the Google Cloud Platform.

Don't forget to terminate the Linux EC2 instance and delete the EBS volume. In the next blog, we will attach an EBS volume to an Windows EC2 instance, which is a bit more easier.

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