How to extend AWS EBS volumes with no downtime

This can be applied whenever you need to extend your EBS volume size avoiding to stop the instance and detach the volume. 

In order to extend the volume size, follow these simple steps: 

1. Login to your AWS console 
2. Choose “EC2” from the services list 
3. Click on “Volumes” under ELASTIC BLOCK STORE menu (on the left) 
4. Choose the volume that you want to resize, right click on “Modify Volume” 
5. You’ll see an option window like this one: If your filesystem is an ext2, ext3, or ext4, type: 
6. Set the new size for your EBS volume (in this case i extended an 8GB volume to 20GB) 
7. Click on modify. 

Now, we need to extend the partition itself. 

SSH to the EC2 instance where the EBS we’ve just extended is attached to. 

Type the following command to list our block devices: 

 lsblk 

You should be able to see a similar output:

NAME    MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
xvda    202:0    0  20G  0 disk
└─xvda1 202:1    0  8G   0 part /

As you can see size of the root volume reflects the new size, 20GB, the size of the partition reflects the original size, 8 GB, and must be extended before you can extend the file system. 

To do so, type the following command: 

sudo growpart /dev/xvda 0

Be careful, there is a space between device name and partition number! 

Now we can check that the partition reflects the increased volume size (we can check it with the lsblk command we already used): 

NAME    MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
xvda    202:0    0  20G  0 disk
└─xvda1 202:1    0  20G  0 part /

Last but not least, we need to extend the filesystem itself. 

sudo resize2fs /dev/xvda1

If your filesystem is an XFS, then type: 

sudo xfs_growfs /dev/xvda1

Finally we can check our extended filesystem by typing: 

df -h

If everything went right, we should be able to see our effective filesystem extended size: 

Filesystem      Size     Used     Avail    Use%    Mounted on
devtmpfs      980M      0         980M    0%       /dev
tmpfs           997M      0         997M    0%       /dev/shm
tmpfs           997M      440K   997M    1%       /run
tmpfs           997M      0        997M     0%      /sys/fs/cgroup
/dev/xvda1   20G        1,4G   9G         7%     /

You have just extended your EBS volume size with 0 downtime.

Source: Hackernoon