How to increase devmapper: Thin Pool or loop-lvm Size in Docker

Sometimes while we do any docker operation or build docker images, we might encounter devmapper: Thin Pool space issue.

daemon: devmapper: Thin Pool has 132480 free data blocks which is less than minimum required 163840 free data blocks. Create more free space in thin pool or use dm.min_free_space option to change behavior

We can resize a loop-lvm thin pool manually without any device-tool utility.

1. First grep the location of Data loop file.

$ sudo docker info | grep loop WARNING: Usage of loopback devices is strongly discouraged for production use. Use `--storage-opt dm.thinpooldev` to specify a custom block storage device. Data file: /dev/loop0 Metadata file: /dev/loop1 Data loop file: /var/lib/docker/devicemapper/devicemapper/data Metadata loop file: /var/lib/docker/devicemapper/devicemapper/metadata

2. Check the total size of loop0 device.

$ echo $[ $(sudo blockdev --getsize64 /dev/loop0) / 1024 / 1024 / 1024 ] 100

3. We will add 100GB in Data file: /dev/loop0, file path as per the above output:- /var/lib/docker/devicemapper/devicemapper/data

$ sudo truncate -s +100G /var/lib/docker/devicemapper/devicemapper/data

4. set up and control loop devices and force loop driver to reread size of the file associated with the specified loop device

$ sudo losetup -c /dev/loop0

5. Check the size of Data file.

$ ls -lhtr /var/lib/docker/devicemapper/devicemapper/data -rw-rw-rw- 1 root root 200G Jan 27 05:06 /var/lib/docker/devicemapper/devicemapper/data

6. Now check the total size of loop0 device.

$ echo $[ $(sudo blockdev --getsize64 /dev/loop0) / 1024 / 1024 / 1024 ] 200

7. Get the pool name first which we will used to update its table.

$ sudo dmsetup status |grep 'thin-pool' |awk -F ': ' {'print $1'} docker-202:81-14418666-pool

8. use low level logical volume management to outputs the current table for the device in a format that can be fed back in using  the  create  or  load  commands.

$ sudo dmsetup table docker-202:81-14418666-pool 0 209715200 thin-pool 7:1 7:0 128 32768 1 skip_block_zeroing

The second number (209715200) is the size of the device, which will need next to calculate the actual size of volume. 

9. Let’s compute how many sectors we need for a 100 GB volume. Per sector 512-bytes in a volume or Disk drive hence we will use first three 1024 for Giga bytes (GB) and divided by 512 bytes.

$ echo $((100*1024*1024*1024/512)) 209715200

10. Now add both the value of step 8 and step 9.

209715200

+209715200 = 419430400

11# The old table was 0 209715200 thin-pool 7:1 7:0 128 32768 1 skip_block_zeroing. We will change the second number, and be extremely careful about leaving everything else exactly as it is.

$ echo 0 419430400 thin-pool 7:1 7:0 128 32768 1 skip_block_zeroing | sudo dmsetup load docker-202:81-14418666-pool

If you face any permission error with above command then please execute it with root user.

12. Run the following command to activate new table.

$ sudo dmsetup resume docker-202:81-14418666-pool

13# Run the below command to check the table output.

$ sudo dmsetup table docker-202:81-14418666-pool 0 419430400 thin-pool 7:1 7:0 128 32768 1 skip_block_zeroing

14. Run command docker info to see the actual Data size.

$ sudo docker info | grep Data Data file: /dev/loop0 Data Space Used: 102.9GB Data Space Total: 204.8GB Data Space Available: 101.9GB Data loop file: /var/lib/docker/devicemapper/devicemapper/data