User namespace remapping in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to enable user namespace remapping in Docker daemon.

Docker

dockerd --userns-[1]

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

Auser

Benable

Cmap

Dremap

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'enable' or 'map' instead of 'remap' causes the command to fail.

Omitting the flag entirely disables user namespace remapping.

The correct flag to enable user namespace remapping is --userns-remap.

2fill in blank

medium

Complete the daemon.json snippet to set user namespace remapping to the default user.

Docker

{
  "userns-remap": "[1]"
}

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

Aroot

Bdefault

Cnobody

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'root' disables remapping.

Using 'nobody' is not a valid remapping user.

Setting "userns-remap": "default" enables remapping to the default user created by Docker.

3fill in blank

hard

Fix the error in this Docker run command to use user namespace remapping correctly.

Docker

docker run --userns [1] alpine id

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

Aremap

Bmap

Cdefault

Duserns-remap

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'remap' causes an unknown mode error.

Using 'userns-remap' is invalid for this flag.

The correct option for the --userns flag is default to enable remapping.

4fill in blank

hard

Fill both blanks to create a user namespace remapping entry in /etc/subuid and /etc/subgid.

Docker

dockremap:[1]:[2]

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

A100000

B65536

C65535

D100001

Attempts:

3 left

💡 Hint

Common Mistakes

Using 65535 instead of 65536 causes off-by-one errors.

Using 100001 as start UID is incorrect for default remapping.

The user namespace remapping uses UID 100000 and a range of 65536 IDs by default.

5fill in blank

hard

Fill all three blanks to complete the Docker daemon configuration for user namespace remapping with a custom user.

Docker

{
  "userns-remap": "[1]",
  "subuid": "[2]",
  "subgid": "[3]"
}

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

Acustomuser

B100000-165535

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'default' as user disables custom remapping.

Mismatching UID and GID ranges causes errors.

To use a custom user for remapping, set userns-remap to the username, and specify the UID and GID ranges in subuid and subgid respectively.