kubectl exec for container access in Kubernetes - Commands & Configuration

Introduction

Sometimes you need to look inside a running container to check logs, files, or run commands. kubectl exec lets you open a terminal inside a container to do this directly.

When you want to debug a running application by checking its files or logs inside the container.

When you need to run a quick command inside a container without changing its image or restarting it.

When you want to inspect the environment variables or configuration inside a container.

When you want to test connectivity or run network commands inside a container.

When you want to manually fix a problem inside a container before automating a solution.

Commands

This command lists all running pods in the current namespace so you can find the pod name to access.

Terminal

kubectl get pods

Expected Output

NAME           READY   STATUS    RESTARTS   AGE

example-pod    1/1     Running   0          10m

This command opens an interactive shell inside the container of the pod named example-pod. The -it flags allow you to interact with the shell.

Terminal

kubectl exec -it example-pod -- /bin/sh

Expected Output

# 

→

-i - Keep stdin open so you can type commands

→

-t - Allocate a terminal so the shell works interactively

This command exits the shell inside the container and returns you to your local terminal.

Terminal

exit

Expected Output

No output (command runs silently)

Key Concept

If you remember nothing else from this pattern, remember: kubectl exec -it pod-name -- /bin/sh lets you open a live terminal inside a container to inspect or fix it.

Common Mistakes

Running kubectl exec without -it flags

Without -it, you cannot interact with the shell, so commands that need input or a terminal will fail or hang.

Always use both -i and -t flags together when opening a shell inside a container.

Using the wrong shell path like /bin/bash when the container only has /bin/sh

If the shell does not exist in the container, the command will fail with an error.

Check the container image documentation or try /bin/sh which is more common and lightweight.

Not specifying the command after --

kubectl exec needs a command to run inside the container; without it, the command will fail.

Always specify the command to run after --, for example /bin/sh or /bin/bash.

Summary

Use kubectl get pods to find the pod name you want to access.

Use kubectl exec -it pod-name -- /bin/sh to open an interactive shell inside the container.

Use exit to leave the container shell and return to your local terminal.

Practice

1. What does the kubectl exec command do in Kubernetes?

easy

A. Lists all running pods in the cluster

B. Deletes a pod from the cluster

C. Creates a new pod in the cluster

D. Runs a command inside a running container in a pod

Solution

1. Step 1: Understand the purpose of kubectl exec

   The kubectl exec command is used to run commands inside a container that is already running inside a pod.

2. Step 2: Compare with other kubectl commands

   Deleting pods uses kubectl delete pod, creating pods uses kubectl create, and listing pods uses kubectl get pods. These are different commands.

3. Final Answer:

   Runs a command inside a running container in a pod -> Option D

4. Quick Check:

   kubectl exec = run command inside container [OK]

Hint: kubectl exec runs commands inside containers [OK]

Common Mistakes:

• Confusing exec with pod creation or deletion
• Thinking exec lists pods
• Using exec without specifying pod

2. Which of the following is the correct syntax to start an interactive shell inside a container named web in pod frontend-pod?

easy

A. kubectl exec -it frontend-pod -c web -- /bin/bash

B. kubectl exec frontend-pod -c web -it /bin/bash

C. kubectl exec -c web frontend-pod /bin/bash -it

D. kubectl exec frontend-pod /bin/bash -c web -it

Solution

1. Step 1: Recall correct kubectl exec syntax

   The correct syntax for interactive shell is: kubectl exec -it POD_NAME -c CONTAINER_NAME -- /bin/bash. The -it flags come before the pod name, and -- separates command from options.

2. Step 2: Analyze each option

   kubectl exec -it frontend-pod -c web -- /bin/bash matches the correct syntax exactly. The other options have misplaced flags or arguments causing syntax errors.

3. Final Answer:

   kubectl exec -it frontend-pod -c web -- /bin/bash -> Option A

4. Quick Check:

   Correct flag order and -- separator = kubectl exec -it frontend-pod -c web -- /bin/bash [OK]

Hint: Use -it before pod name and -- before command [OK]

Common Mistakes:

• Placing -it after pod name
• Omitting -- before command
• Misordering container flag -c

3. What will be the output of this command if the pod db-pod has a container named mysql running and you execute:
kubectl exec db-pod -c mysql -- ls /var/lib/mysql?

medium

A. Lists files and directories inside /var/lib/mysql in the mysql container

B. Shows an error: container mysql not found

C. Lists files in the host machine's /var/lib/mysql directory

D. Starts an interactive shell inside the mysql container

Solution

1. Step 1: Understand the command

   The command runs ls /var/lib/mysql inside the mysql container of the db-pod pod. It lists files in that directory inside the container.

2. Step 2: Eliminate wrong options

   Shows an error: container mysql not found is wrong because the container exists. Lists files in the host machine's /var/lib/mysql directory is wrong because kubectl exec runs inside container, not host. Starts an interactive shell inside the mysql container is wrong because no shell is started; only ls runs.

3. Final Answer:

   Lists files and directories inside /var/lib/mysql in the mysql container -> Option A

4. Quick Check:

   kubectl exec runs command inside container = Lists files and directories inside /var/lib/mysql in the mysql container [OK]

Hint: kubectl exec runs command inside container, not host [OK]

Common Mistakes:

• Thinking command runs on host machine
• Confusing exec with shell start
• Assuming container does not exist

4. You run kubectl exec -it mypod -- /bin/sh but get the error: error: a container name must be specified for pod mypod, choose one of: [app backend]. What is the fix?

medium

A. Restart the pod before running exec

B. Add -c app or -c backend to specify the container

C. Remove -it flags to fix the error

D. Use kubectl exec mypod /bin/sh without flags

Solution

1. Step 1: Understand the error message

   The error says multiple containers exist in pod mypod, so you must specify which container to exec into using -c.

2. Step 2: Apply the fix

   Add -c app or -c backend to the command to specify the container name explicitly.

3. Final Answer:

   Add -c app or -c backend to specify the container -> Option B

4. Quick Check:

   Multiple containers need -c flag = Add -c app or -c backend to specify the container [OK]

Hint: Specify container with -c when pod has multiple containers [OK]

Common Mistakes:

• Ignoring container name when multiple containers exist
• Removing -it flags unnecessarily
• Restarting pod without reason

5. You want to run an interactive bash shell inside the container named worker in pod job-pod. The pod has two containers: worker and logger. Which command correctly achieves this?

hard

A. kubectl exec job-pod -c worker -it /bin/bash

B. kubectl exec -it job-pod /bin/bash -c worker

C. kubectl exec -it job-pod -c worker -- /bin/bash

D. kubectl exec job-pod -it -c worker /bin/bash

Solution

1. Step 1: Recall correct syntax for interactive exec with container

   The correct syntax is kubectl exec -it POD_NAME -c CONTAINER_NAME -- /bin/bash. The -it flags come before pod name, -c specifies container, and -- separates command.

2. Step 2: Check options for correct order and flags

   kubectl exec -it job-pod -c worker -- /bin/bash matches the correct syntax exactly. The other options have misplaced flags or missing --, causing errors.

3. Final Answer:

   kubectl exec -it job-pod -c worker -- /bin/bash -> Option C

4. Quick Check:

   Correct flag order and -- separator = kubectl exec -it job-pod -c worker -- /bin/bash [OK]

Hint: Use -it before pod, -c container, and -- before command [OK]

Common Mistakes:

• Misordering flags -it and -c
• Omitting -- before command
• Not specifying container when multiple exist