Limit Docker Single Container Disk Space Usage¶

Docker introduced overlay2.size in version 17.07.0-ce. This article introduces how to use overlay2.size to limit the disk space that a single Docker container can occupy.

Prerequisites¶

Before configuring docker overlay2.size, you need to adjust the file system type to xfs in the operating system and use pquota method for device mounting.

To format the device as XFS file system, you can execute the following command:

mkfs.xfs -f /dev/xxx

Set Single Container Disk Space¶

After meeting the above conditions, users can limit single container disk space by setting docker overlay2.size. Command line example:

sudo dockerd -s overlay2 --storage-opt overlay2.size=1G

Scenario Walkthrough¶

Next, let's walk through the overall implementation process of limiting Docker single container disk space usage with a practical example.

Target¶

Deploy a Kubernetes cluster and limit the disk space that a single Docker container can occupy to 1G. It cannot be used once it exceeds 1G.

Procedure¶

1. Log in to the target node and view the fstab file to obtain the current mounting status of the device.

   $ cat /etc/fstab
   
   # /etc/fstab
   # Created by anaconda on Thu Mar 19 11:32:59 2020
   #
   # Accessible filesystems, by reference, are maintained under '/dev/disk'
   # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
   #
   /dev/mapper/centos-root /                       xfs     defaults        0 0
   UUID=3ed01f0e-67a1-4083-943a-343b7fed1708 /boot                   xfs     defaults        0 0
   /dev/mapper/centos-swap swap                    swap    defaults        0 0
   

   Taking the node device in the figure as an example, you can see that the XFS format device /dev/mapper/centos-root is mounted to the / root directory in the default way (defaults).

2. Configure the xfs file system to be mounted using the pquota method.

   1. Modify the fstab file to update the mounting method from defaults to rw,pquota;

      # Modify the fstab configuration
      $ vi /etc/fstab
      - /dev/mapper/centos-root /                       xfs     defaults         0 0
      + /dev/mapper/centos-root /                       xfs     rw,pquota        0 0
      
      # Verify whether the configuration is correct
      $ mount -a
      

   2. Check whether pquota takes effect.

      xfs_quota -x -c print
      

      

   Note

   If pquota does not take effect, check whether the pquota option is enabled in the operating system. If it is not enabled, you need to add the rootflags=pquota parameter to the system boot configuration /etc/grub2.cfg. After the configuration is complete, you need to reboot the operating system.

   

3. Add the docker_storage_options parameter in Create Cluster -> Advanced Settings -> Custom Parameters to set the disk space that a single container can occupy.

   

   Note

   You can also operate based on the kubean manifest and add the docker_storage_options parameter in vars conf.

   apiVersion: v1
   kind: ConfigMap
   metadata:
     name: sample-vars-conf
     namespace: kubean-system
   data:
     group_vars.yml: |
       unsafe_show_logs: true
       container_manager: docker
   +   docker_storage_options: -s overlay2 --storage-opt overlay2.size=1G  # Add the docker_storage_options parameter
       kube_network_plugin: calico
       kube_network_plugin_multus: false
       kube_proxy_mode: iptables
       etcd_deployment_type: kubeadm
       override_system_hostname: true
       ...
   

4. View the running configuration of the dockerd service to check whether the disk limit is set successfully.

   

With the above steps, the overall implementation process of limiting the disk space that a single Docker container can occupy is complete.

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