Storage driver options in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to set the storage driver to overlay2 when starting the Docker daemon.

Docker

dockerd --storage-driver=[1]

Drag options to blanks, or click blank then click option'

Abtrfs

Baufs

Coverlay2

Ddevicemapper

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'aufs' which is deprecated on many systems.

Using 'devicemapper' without proper configuration.

The overlay2 driver is the recommended storage driver for modern Linux kernels. The command dockerd --storage-driver=overlay2 starts the Docker daemon using this driver.

2fill in blank

medium

Complete the Docker daemon configuration file snippet to specify the storage driver as btrfs.

Docker

{
  "storage-driver": "[1]"
}

Drag options to blanks, or click blank then click option'

Abtrfs

Boverlay

Caufs

Ddevicemapper

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'overlay' instead of 'overlay2' which is the newer version.

Forgetting to restart the Docker daemon after changing the config.

Setting "storage-driver": "btrfs" in the Docker daemon JSON config file tells Docker to use the Btrfs storage driver.

3fill in blank

hard

Fix the error in the command to start Docker with devicemapper storage driver.

Docker

dockerd --storage-driver=[1]

Drag options to blanks, or click blank then click option'

Aoverlay2

Baufs

Cbtrfs

Ddevicemapper

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'devicemapper' without proper kernel support.

Typing 'device-mapper' or other incorrect spellings.

The devicemapper driver requires specific setup but can be set by dockerd --storage-driver=devicemapper. This fixes errors caused by missing or wrong driver names.

4fill in blank

hard

Fill both blanks to create a Docker daemon config snippet that sets the storage driver to overlay2 and enables experimental features.

Docker

{
  "storage-driver": "[1]",
  "experimental": [2]
}

Drag options to blanks, or click blank then click option'

Aoverlay2

Btrue

Cfalse

Daufs

Attempts:

3 left

💡 Hint

Common Mistakes

Setting experimental to false when intending to enable it.

Using an unsupported storage driver.

The config sets "storage-driver": "overlay2" and enables experimental features with "experimental": true.

5fill in blank

hard

Fill all three blanks to create a Docker daemon config snippet that sets the storage driver to devicemapper, disables live-restore, and sets the log level to info.

Docker

{
  "storage-driver": "[1]",
  "live-restore": [2],
  "log-level": "[3]"
}

Drag options to blanks, or click blank then click option'

Aoverlay2

Bfalse

Cinfo

Ddevicemapper

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing live-restore true/false values.

Using incorrect log level strings.

This config sets the storage driver to devicemapper, disables live-restore by setting it to false, and sets the log level to info.

Practice

1. What is the main purpose of a Docker storage driver?

easy

A. To manage how Docker stores container data on disk

B. To control network settings for containers

C. To schedule container start times

D. To monitor container CPU usage

Solution

1. Step 1: Understand Docker storage drivers

   Storage drivers define how Docker saves and manages container data on the host disk.

2. Step 2: Identify the correct function

   Among the options, only managing container data storage matches the role of storage drivers.

3. Final Answer:

   To manage how Docker stores container data on disk -> Option A

4. Quick Check:

   Storage driver = manages container data storage [OK]

Hint: Storage drivers handle container data storage, not networking or CPU [OK]

Common Mistakes:

• Confusing storage drivers with network drivers
• Thinking storage drivers manage container resource limits
• Assuming storage drivers schedule container tasks

2. Which of the following is the correct syntax to specify the storage driver when starting the Docker daemon manually?

easy

A. docker run --storage-driver=overlay2

B. dockerd --storage-driver=overlay2

C. dockerd -storage driver overlay2

D. docker daemon --storage=overlay2

Solution

1. Step 1: Recall Docker daemon start syntax

   The Docker daemon is started with the command 'dockerd' and options use double dashes with hyphens.

2. Step 2: Match correct option format

   dockerd --storage-driver=overlay2 uses 'dockerd --storage-driver=overlay2' which is the correct syntax to set the storage driver.

3. Final Answer:

   dockerd --storage-driver=overlay2 -> Option B

4. Quick Check:

   Daemon start uses 'dockerd --storage-driver' [OK]

Hint: Use 'dockerd --storage-driver=drivername' to set storage driver [OK]

Common Mistakes:

• Using 'docker run' instead of 'dockerd' to set storage driver
• Incorrect flag syntax like '-storage driver'
• Using 'docker daemon' which is deprecated

3. Given the Docker daemon started with dockerd --storage-driver=aufs, what will be the output of docker info | grep 'Storage Driver'?

medium

A. Storage Driver: aufs

B. Storage Driver: btrfs

C. Storage Driver: devicemapper

D. Storage Driver: overlay2

Solution

1. Step 1: Understand the command effect

   The command 'docker info | grep "Storage Driver"' filters Docker info output to show the storage driver in use.

2. Step 2: Match the storage driver set at daemon start

   Since the daemon was started with '--storage-driver=aufs', the output will show 'Storage Driver: aufs'.

3. Final Answer:

   Storage Driver: aufs -> Option A

4. Quick Check:

   Set driver = output driver [OK]

Hint: Output matches the driver set at daemon start [OK]

Common Mistakes:

• Assuming default driver instead of the one set
• Confusing output with other storage drivers
• Not using correct grep syntax

4. You tried to start Docker with dockerd --storage-driver=overlay3 but it failed. What is the most likely reason?

medium

A. The storage driver option requires a space, not an equals sign

B. You need to use 'docker run' instead of 'dockerd'

C. Docker does not support storage drivers on Linux

D. overlay3 is not a valid Docker storage driver

Solution

1. Step 1: Verify valid storage drivers

   Docker supports drivers like overlay2, aufs, devicemapper, but 'overlay3' is not a valid driver.

2. Step 2: Check command usage

   The command 'dockerd --storage-driver=overlay3' is correct syntax, but the driver name is invalid, causing failure.

3. Final Answer:

   overlay3 is not a valid Docker storage driver -> Option D

4. Quick Check:

   Invalid driver name causes failure [OK]

Hint: Check driver name spelling and validity before starting daemon [OK]

Common Mistakes:

• Using invalid or unsupported driver names
• Confusing 'dockerd' with 'docker run'
• Incorrect flag syntax

5. You want to optimize Docker performance on a system with an ext4 filesystem. Which storage driver option should you choose in the Docker daemon configuration file for best compatibility and performance?

hard

A. aufs

B. devicemapper

C. overlay2

D. btrfs

Solution

1. Step 1: Identify filesystem compatibility

   Overlay2 is recommended for ext4 filesystems because it is stable and performs well on ext4.

2. Step 2: Compare other drivers

   Devicemapper is older and less efficient; aufs is deprecated on many systems; btrfs requires btrfs filesystem, not ext4.

3. Final Answer:

   overlay2 -> Option C

4. Quick Check:

   ext4 + overlay2 = best performance [OK]

Hint: Use overlay2 for ext4 filesystem for best Docker performance [OK]

Common Mistakes:

• Choosing btrfs on ext4 filesystem
• Using devicemapper despite better options
• Assuming aufs is always best