Cis Docker V160 2.11

Ensure base device size is not changed until needed

Profile Applicability: Level 2 - Docker - Linux

Assessment Status: Manual

Description

Under certain circumstances, you might need containers larger than 10G. Where this applies you should carefully choose the base device size.

Rationale

The base device size can be increased on daemon restart. Increasing the base device size allows all future images and containers to be of the new base device size. A user can use this option to expand the base device size however shrinking is not permitted. This value affects the system wide "base" empty filesystem that may already be initialized and therefore inherited by pulled images.

Although the file system does not allocate the increased size as long as it is empty, more space will be allocated for extra images. This may cause a denial of service condition if the allocated partition becomes full.

Impact

None.

Audit Procedure

To confirm this setting the dockerd start-up options and any settings in /etc/docker/daemon.json should be reviewed. To review the dockerd startup options, use:

ps -ef | grep dockerd

Execute the above command and it should not show any --storage-opt dm.basesize parameters. The contents of /etc/docker/daemon.json should also be reviewed

Remediation

Do not set --storage-opt dm.basesize until needed.

Default Value

The default base device size is 10G.

References

1. https://docs.docker.com/engine/reference/commandline/dockerd/#storage-driver-options

CIS Controls

Profile/Assessment Status

Profile: Level 2 - Docker - Linux Assessment Status: Manual