Storage driver options in Docker - Step-by-Step Execution

Process Flow - Storage driver options

Docker daemon starts

↓

Reads storage driver config

↓

Select storage driver

↓

Initialize driver

↓

Manage container layers

↓

Store container data

↓

Containers run with storage

↓

Docker daemon stops

Docker reads the configured storage driver when it starts, initializes it, and uses it to manage container file layers and data storage.

Execution Sample

Docker

docker info --format '{{.Driver}}'
docker run --rm alpine ls /
docker info --format '{{.DriverStatus}}'

Shows the current storage driver, runs a container, then shows detailed driver status.

Process Table

Step	Command	Action	Output / Result
1	docker info --format '{{.Driver}}'	Check current storage driver	overlay2
2	docker run --rm alpine ls /	Run container and list root directory	bin etc lib proc root sys tmp usr var
3	docker info --format '{{.DriverStatus}}'	Show detailed storage driver status	["Backing Filesystem", "ext4"], ["Supports d_type", "true"], ["Native Overlay Diff", "true"]

💡 Commands complete showing storage driver in use and container filesystem accessed.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3
Storage Driver	unknown	overlay2	overlay2	overlay2
Container Filesystem	none	none	mounted and listed	mounted and listed

Key Moments - 3 Insights

Why does Docker need to know the storage driver before running containers?

Docker uses the storage driver to manage how container files and layers are stored and accessed. Without it, containers cannot read or write files properly. See execution_table step 1 and 2.

What does the 'overlay2' driver mean in the output?

'overlay2' is a modern storage driver that uses overlay filesystem technology to efficiently manage container layers. It is shown in execution_table step 1 output.

Why do we run 'docker info --format '{{.DriverStatus}}'' after running a container?

This command shows detailed info about the storage driver capabilities and status, confirming it is working correctly with the container filesystem. See execution_table step 3.

Visual Quiz - 3 Questions

Look at the execution_table step 1, what storage driver is Docker using?

A aufs

B overlay2

C devicemapper

D btrfs

💡 Hint

Check the output column in execution_table step 1.

At which step do we see the container filesystem contents listed?

A Step 1

B Step 3

C Step 2

D None

💡 Hint

Look for the 'ls /' command output in execution_table.

If Docker used 'aufs' instead of 'overlay2', which step output would change?

A Step 1 and Step 3

B Step 2 only

C Step 1 only

D All steps

💡 Hint

Storage driver name appears in step 1 and detailed driver info in step 3.

Concept Snapshot

Docker Storage Driver Options:
- Docker selects a storage driver at daemon start.
- Storage driver manages container file layers.
- Common drivers: overlay2 (modern), aufs, devicemapper.
- Check current driver: docker info --format '{{.Driver}}'
- Detailed status: docker info --format '{{.DriverStatus}}'
- Driver affects container filesystem performance and features.

Full Transcript

When Docker starts, it reads the configured storage driver option. This driver controls how Docker stores and manages container files and layers. For example, the 'overlay2' driver uses overlay filesystem technology to efficiently handle container data. Running 'docker info --format '{{.Driver}}'' shows which driver is active. Running a container like 'docker run --rm alpine ls /' mounts the container filesystem using that driver. Finally, 'docker info --format '{{.DriverStatus}}'' shows detailed info about the driver's capabilities and status. Understanding storage drivers helps troubleshoot container storage and performance issues.