WORKDIR instruction for directory in Docker - Step-by-Step Execution

Process Flow - WORKDIR instruction for directory

Start Dockerfile

↓

Read WORKDIR instruction

↓

Check if directory exists

Yes No↓

Set as current

↓

Use directory for next commands

↓

Continue build

Docker reads the WORKDIR line, checks if the directory exists, creates it if needed, then sets it as the working directory for following commands.

Execution Sample

Docker

FROM alpine
WORKDIR /app
RUN touch file.txt

Sets /app as working directory, creates it if missing, then runs command inside /app.

Process Table

Step	Instruction	Action	Directory State	Current Working Directory
1	FROM alpine	Start from alpine base image	/	/
2	WORKDIR /app	Check /app exists? No, create /app	/app created	/app
3	RUN touch file.txt	Run command inside /app	/app exists with file.txt	/app
4	End	Build continues with /app as working dir	/app exists with file.txt	/app

💡 WORKDIR sets /app as current directory; created if missing; subsequent commands run there.

Status Tracker

Variable	Start	After Step 2	After Step 3	Final
Current Directory	/	/app	/app	/app
Directory /app Exists	No	Yes	Yes	Yes
Files in /app	None	None	file.txt	file.txt

Key Moments - 2 Insights

Why does Docker create the directory if it does not exist when using WORKDIR?

Docker ensures the directory exists so commands run inside it without errors, as shown in execution_table step 2 where /app is created.

Does WORKDIR change the directory for the whole build or just the next command?

WORKDIR sets the directory for all following commands, not just the next one, as seen in steps 3 and 4 where current directory remains /app.

Visual Quiz - 3 Questions

Look at the execution table, what is the current working directory after the WORKDIR instruction?

A /app

B /

C /root

D /home

💡 Hint

Check the 'Current Working Directory' column at step 2 in the execution_table.

At which step does Docker create the /app directory?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Directory State' column in execution_table for when /app is created.

If the WORKDIR was set to an existing directory, what would change in the execution table?

A Docker would create a new directory anyway

B Docker would delete the directory first

C Docker would skip creating the directory

D Docker would fail the build

💡 Hint

Refer to the decision in concept_flow where directory existence affects creation.

Concept Snapshot

WORKDIR /path
- Sets working directory for following commands
- Creates directory if missing
- Affects all subsequent RUN, CMD, ENTRYPOINT
- Simplifies file paths in Dockerfile
- Helps organize container filesystem

Full Transcript

The WORKDIR instruction in Dockerfile sets the working directory for all following commands. When Docker reads WORKDIR, it checks if the directory exists inside the image. If it does not exist, Docker creates it automatically. Then Docker uses this directory as the current working directory for subsequent commands like RUN or CMD. This means commands run inside that directory without needing full paths. For example, WORKDIR /app creates /app if missing and sets it as current directory. Then RUN touch file.txt creates file.txt inside /app. This behavior helps organize files and commands inside containers cleanly.