Plan output reading in Terraform - Step-by-Step Execution

Process Flow - Plan output reading

Run terraform plan

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Terraform analyzes config

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Detect changes: add, modify, delete

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Generate plan output

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User reads plan output

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Decide to apply or not

Terraform plan reads your config, compares with current state, and shows what will change before applying.

Execution Sample

Terraform

terraform plan

# Sample output snippet:
# + aws_instance.example
# - aws_s3_bucket.old_bucket
# ~ aws_security_group.sg

Shows what resources will be added (+), removed (-), or changed (~) before applying.

Process Table

Step	Action	Resource	Change Type	Details
1	Detect new resource	aws_instance.example	Add (+)	Will create new EC2 instance
2	Detect resource to remove	aws_s3_bucket.old_bucket	Delete (-)	Will delete old S3 bucket
3	Detect resource to update	aws_security_group.sg	Modify (~)	Will update security group rules
4	Show plan summary			Plan: 1 to add, 1 to change, 1 to destroy
5	Wait for user decision			User decides to apply or not

💡 Plan output complete, user can review changes before apply

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
Resources to Add	0	1	1	1	1
Resources to Change	0	0	0	1	1
Resources to Delete	0	0	1	1	1

Key Moments - 3 Insights

Why do some resources have a '+' sign and others '-' or '~' in the plan output?

The '+' means a resource will be created, '-' means it will be deleted, and '~' means it will be modified. See execution_table rows 1-3 for examples.

Does terraform apply changes automatically after plan?

No, terraform plan only shows what will happen. The user must run 'terraform apply' to make changes. See execution_table row 5.

What if the plan shows no changes?

If no resources are added, changed, or deleted, terraform will show 'No changes. Infrastructure is up-to-date.' This means your config matches the current state.

Visual Quiz - 3 Questions

Look at the execution_table, what change type is assigned to 'aws_security_group.sg' at step 3?

A Add (+)

B Delete (-)

C Modify (~)

D No change

💡 Hint

Check the 'Change Type' column in execution_table row 3.

At which step does terraform detect a resource to delete?

A Step 2

B Step 3

C Step 1

D Step 4

💡 Hint

Look for 'Delete (-)' in the 'Change Type' column in execution_table.

If no resources need to be added, changed, or deleted, how would the variable 'Resources to Add' look after step 3?

A 1

B 0

C Depends on user input

D Undefined

💡 Hint

Refer to variable_tracker row 'Resources to Add' values after step 3.

Concept Snapshot

terraform plan shows what changes will happen without applying them
+ means add, - means delete, ~ means modify
Review plan output carefully before running terraform apply
Plan output helps avoid surprises in your cloud infrastructure
Always read plan output to confirm changes

Full Transcript

Terraform plan reads your configuration and compares it to the current cloud state. It detects which resources will be added, changed, or deleted. The plan output uses symbols: plus (+) for new resources, minus (-) for deletions, and tilde (~) for modifications. This output helps you understand what terraform will do before you apply changes. You must run 'terraform apply' to make the changes happen. If no changes are needed, terraform will say the infrastructure is up-to-date. Reading the plan output carefully helps avoid mistakes and surprises in your cloud setup.