Resize your persist disk on Google Cloud on the fly

How many time do you have to stop your VM and attach a new disk because you ran out of space when downloading a huge dataset or training a model.

Well, you don’t have to do so. Cloud computing has been evolving for many years and resize disk on the fly is now a trivial task for users to do. I believe Cloud provider has developed pretty advanced virtual disk technology, but I’ll skip that since I’m not an expert.

This post is a pretty short step-by-step guide on how to do so on Google Cloud Compute Engine. It only applies for arguably the most common case — The entire disk is reserved for a single partition /.

Step 0.1: Check remaining disks available

$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 77G 0 77G 0% /dev
tmpfs 16G 9.1M 16G 1% /run
/dev/sda1 970G 552G 418G 57% /
tmpfs 77G 228K 77G 1% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 77G 0 77G 0% /sys/fs/cgroup

Line starting with /dev/sda1 is the one you’re looking for. From the example above, you notice that you have used more than half of the disk mounted as /

If you see the use rate is over 80%, that’s probably a dangerous sign.

Step 0.2: Check partition

$ sudo lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 1000G 0 disk 
└─sda1 8:1 0 1000G 0 part /

You noticed that device sda only contains one partition sda1, which made things much simpler.

Step 1: Increase disk size

In your VM . instance setting, click on the disk (either boot disk or additional disk), then increase the capacity by the amount you need.

Step 2: Grow the partition

Go to your VM console

$ sudo growpart /dev/sda 1
CHANGED: partition=1 start=2048 old: size=419428319 end=419430367 new: size=2097149919
,end=2097151967

Step 3: Resize file system

$ sudo resize2fs /dev/sda1
resize2fs 1.42.13 (17-May-2015)
Filesystem at /dev/sda1 is mounted on /; on-line resizing required
old_desc_blocks = 13, new_desc_blocks = 63
The filesystem on /dev/sda1 is now 262143739 (4k) blocks long.

Step 4: Verify

$ df -h

All done. Enjoy!