Preload the source image before creating a Docker image mount

Bottom line: Make source-image availability an explicit deployment prerequisite for an image mount. Record which daemon must hold it before attempting container creation, rather than treating the mounted asset as an automatic download.

Source fact: documented behavior

The Image mounts documentation is the primary reference.

Docker documents image mounts as requiring the containerd image store. The mount’s source image must already exist in the daemon’s image store; mount creation does not pull it automatically and fails when it is absent. The mounted image content is read-only and is not modified through the mount.

What the source does not establish

This article concerns availability of the mounted source image. It does not approve that image’s contents, establish binary compatibility with the application or prescribe a registry trust policy. Keep ordinary bind-mount host access and application-image selection under their own reviews. Confirm the installed Engine and store support before adopting the mechanism.

Applicability questions

• Which daemon and image store will create the container?
• What approved source image reference should supply the mounted files?
• How will that image be made available before deployment?
• What harmless file can demonstrate that the expected asset was mounted?

DSE recommendation: treat the mounted asset as a separate input

DSE recommends listing the application image and mounted source image as separate deployment inputs. Give the source asset its own owner, approved reference and intended destination. Require an explicit preload step in the managed workflow instead of assuming an application-image pull accounts for every input.

Check the selected daemon before investigating a missing-source failure. Compare the operator’s approved context with the deployment’s target and use supported inventory tooling to review the source image there. Do not pull an unreviewed substitute merely because its tag resembles the expected one.

Keep asset availability distinct from asset acceptance. Have the application owner identify the file or directory it expects and the approved evidence for that content. If the mounted input contains executable material, require the separate runtime-compatibility and provenance review before execution. A successful mount should not close those questions.

Include replacement and recovery in the input record. Preserve the previous approved source reference and describe which controlled deployment should consume a changed asset. Keep any cleanup procedure from removing a required input simply because it is not the application’s own image.

Verification and evidence

Proposed verification: use a disposable daemon with the documented store prerequisite and a harmless asset image. Prepare one approved case where the source is absent and another where that exact source has been preloaded. Write the expected creation result for each case before running it.

Record the selected daemon, source reference, actual creation outcome and the application’s view of a harmless marker file. Keep the application image unchanged so the source-availability difference is isolated. Inspect the actual mount through approved tooling and retain sanitized output. Do not interpret a successful marker read as evidence that unrelated files or executable dependencies were accepted.

Official references

• Image mounts — Docker Docs.

Source review completed October 30, 2026. Recheck the official documentation and deployment-specific applicability before a production change.