Hello everyone! After I created my VM template (250+ lines!), I had a problem. Every time I wanted to deploy a VM with SQL Database, I copied the same code many times. This was bad:<\/p>
Then I learned about Linked Templates. This solved all my problems!<\/p>
Linked templates help you split one big template into small pieces. Each piece is a separate file. You can use the same piece many times.<\/p>
Simple example:<\/p>
Before (one big file):<\/p>
my-big-template.json (500 lines)\n- Network code\n- Storage code\n- SQL code\n- VM code\n- Web App code<\/code><\/pre>After (many small files):<\/p>
main.json (50 lines)\n- Links to sql.json (80 lines)\n- Links to network.json (100 lines)\n- Links to storage.json (30 lines)<\/code><\/pre>It’s like Lego blocks! Each block is separate, but you connect them together.<\/p>
My First Linked Template<\/h3>
I want to create:<\/p>
- Web App – In main template<\/li>
- SQL Database – In linked template (separate file)<\/li><\/ol>
Why? Because I can use the SQL template again in other projects!<\/p>
Step 1: Create SQL Template File<\/h3>
This is my SQL template. It will be the “linked” file:<\/p>
File name: 03-sqldatabase.json<\/p>
{\n \"$schema\": \"https:\/\/schema.management.azure.com\/schemas\/2019-04-01\/deploymentTemplate.json#\",\n \"contentVersion\": \"1.0.0.0\",\n \"parameters\": {\n \"SQLLogin\": {\n \"type\": \"string\",\n \"metadata\": {\n \"description\": \"The administrator user name for the Azure SQL Server\"\n }\n },\n \"SQLPassword\": {\n \"type\": \"secureString\",\n \"metadata\": {\n \"description\": \"The administrator password for the Azure SQL Server\"\n }\n }\n },\n \"functions\": [],\n \"variables\": { },\n \"resources\": [\n {\n \"name\": \"sqlserver500505\",\n \"type\": \"Microsoft.Sql\/servers\",\n \"apiVersion\": \"2021-08-01-preview\",\n \"location\": \"[resourceGroup().location]\",\n \"properties\": {\n \"administratorLogin\": \"[parameters('SQLLogin')]\",\n \"administratorLoginPassword\": \"[parameters('SQLPassword')]\"\n }\n },\n {\n \"name\": \"[format('{0}\/{1}', 'sqlserver500505', 'appdb')]\",\n \"type\": \"Microsoft.Sql\/servers\/databases\",\n \"apiVersion\": \"2021-08-01-preview\",\n \"location\": \"[resourceGroup().location]\",\n \"dependsOn\": [\n \"[resourceId('Microsoft.Sql\/servers', 'sqlserver500505')]\"\n ],\n \"sku\": {\n \"name\": \"Basic\",\n \"tier\": \"Basic\"\n },\n \"properties\": {}\n }\n ],\n \"outputs\": {}\n}<\/code><\/pre>This is just a normal ARM template for SQL Server and Database. Nothing special yet!<\/p>
Important: It uses parameters, not hardcoded values. This makes it reusable.<\/p>
Step 2: Create Parameter File<\/h3>
I create a separate file for the parameter values:<\/p>
File name: 02-sqldatabase-parameters.json<\/p>
{\n \"$schema\": \"https:\/\/schema.management.azure.com\/schemas\/2019-04-01\/deploymentParameters.json#\",\n \"contentVersion\": \"1.0.0.0\",\n \"parameters\": {\n \"SQLLogin\": {\n \"value\": \"sqlusr\"\n },\n \"SQLPassword\": {\n \"value\": \"Azure@123\"\n }\n }\n}<\/code><\/pre>This file has the actual username and password.<\/p>
Why separate files?<\/p>
- Template = What to create<\/li>
- Parameters = The values to use<\/li><\/ul>
I can have different parameter files for dev, test, and production!<\/p>
Step 3: Upload Files to Azure Blob Storage<\/h3>
Linked templates must be on the internet. Azure needs to download them. I use Azure Blob Storage.<\/p>
Create Storage Account<\/h3># Create storage account\naz storage account create \\\n --name rezatemplate9473 \\\n --resource-group template-grp \\\n --location \"North Europe\" \\\n --sku Standard_LRS\n\n# Get the key\nSTORAGE_KEY=$(az storage account keys list \\\n --resource-group template-grp \\\n --account-name rezatemplate9473 \\\n --query '[0].value' \\\n --output tsv)\n\n# Create container (like a folder)\naz storage container create \\\n --name template \\\n --account-name rezatemplate9473 \\\n --account-key $STORAGE_KEY \\\n --public-access blob<\/code><\/pre>Important: –public-access blob means anyone can read the files. This is OK for learning. For production, use better security!<\/p>
Upload Files<\/h3># Upload SQL template\naz storage blob upload \\\n --account-name rezatemplate9473 \\\n --account-key $STORAGE_KEY \\\n --container-name template \\\n --name 03-sqldatabase.json \\\n --file 03-sqldatabase.json\n\n# Upload parameter file\naz storage blob upload \\\n --account-name rezatemplate9473 \\\n --account-key $STORAGE_KEY \\\n --container-name template \\\n --name 02-sqldatabase-parameters.json \\\n --file 02-sqldatabase-parameters.json<\/code><\/pre>Now my files are on the internet!<\/p>
Get the URL<\/h3>az storage blob url \\\n --account-name rezatemplate9473 \\\n --container-name template \\\n --name 03-sqldatabase.json \\\n --output tsv<\/code><\/pre>This gives me:<\/p>
https:\/\/rezatemplate9473.blob.core.windows.net\/template\/03-sqldatabase.json<\/code><\/pre>I will use this URL in my main template!<\/p>
Step 4: Create Main Template<\/h3>
Now I create the main template. This template will “call” the SQL template:<\/p>
File name: 01-main.json<\/p>
{\n \"$schema\": \"https:\/\/schema.management.azure.com\/schemas\/2019-04-01\/deploymentTemplate.json#\",\n \"contentVersion\": \"1.0.0.0\",\n \"parameters\": {},\n \"functions\": [],\n \"variables\": {},\n \"resources\": [\n {\n \"name\": \"plan787878\",\n \"type\": \"Microsoft.Web\/serverfarms\",\n \"apiVersion\": \"2020-12-01\",\n \"location\": \"[resourceGroup().location]\",\n \"sku\": {\n \"name\": \"S1\",\n \"capacity\": 1\n },\n \"properties\": {\n \"name\": \"plan787878\"\n }\n },\n {\n \"name\": \"newapp994848\",\n \"type\": \"Microsoft.Web\/sites\",\n \"apiVersion\": \"2020-12-01\",\n \"location\": \"[resourceGroup().location]\",\n \"dependsOn\": [\n \"[resourceId('Microsoft.Web\/serverfarms', 'plan787878')]\"\n ],\n \"properties\": {\n \"name\": \"newapp994848\",\n \"serverFarmId\": \"[resourceId('Microsoft.Web\/serverfarms', 'plan787878')]\"\n }\n },\n {\n \"type\": \"Microsoft.Resources\/deployments\",\n \"apiVersion\": \"2021-04-01\",\n \"name\": \"LinkedTemplate\",\n \"properties\": {\n \"mode\": \"Incremental\",\n \"templateLink\": {\n \"uri\": \"https:\/\/rezatemplate9473.blob.core.windows.net\/template\/03-sqldatabase.json\",\n \"contentVersion\": \"1.0.0.0\"\n },\n \"parametersLink\": {\n \"uri\": \"https:\/\/rezatemplate9473.blob.core.windows.net\/template\/02-sqldatabase-parameters.json\",\n \"contentVersion\": \"1.0.0.0\"\n }\n }\n }\n ],\n \"outputs\": {}\n}<\/code><\/pre>The Important Part – Linked Deployment<\/h3>
Look at this section:<\/p>
{\n \"type\": \"Microsoft.Resources\/deployments\",\n \"apiVersion\": \"2021-04-01\",\n \"name\": \"LinkedTemplate\",\n \"properties\": {\n \"mode\": \"Incremental\",\n \"templateLink\": {\n \"uri\": \"https:\/\/rezatemplate9473.blob.core.windows.net\/template\/03-sqldatabase.json\",\n \"contentVersion\": \"1.0.0.0\"\n },\n \"parametersLink\": {\n \"uri\": \"https:\/\/rezatemplate9473.blob.core.windows.net\/template\/02-sqldatabase-parameters.json\",\n \"contentVersion\": \"1.0.0.0\"\n }\n }\n}<\/code><\/pre>What does this do?<\/p>
- type: Microsoft.Resources\/deployments – This is a special resource. It calls another template.<\/li>
- name: LinkedTemplate – Just a name. I can use any name.<\/li>
- mode: Incremental – This means “only create new resources, don’t delete existing ones”. Always use this!<\/li>
- templateLink: uri – URL to my SQL template<\/li>
- parametersLink: uri – URL to my parameter file<\/li><\/ol>
Simple explanation:<\/p>
“Hey Azure, please download the SQL template from this URL, download the parameters from this URL, and deploy them!”<\/p>
Step 5: Deploy Everything<\/h3>
Now I deploy the main template:<\/p>
# Create resource group\naz group create \\\n --name linked-template-grp \\\n --location \"North Europe\"\n\n# Deploy main template\naz deployment group create \\\n --resource-group linked-template-grp \\\n --template-file 01-main.json<\/code><\/pre>What happens:<\/p>
- Azure starts deploying main template<\/li>
- Azure creates App Service Plan<\/li>
- Azure creates Web App<\/li>
- Azure sees the linked deployment resource<\/li>
- Azure downloads SQL template from blob storage<\/li>
- Azure downloads parameter file from blob storage<\/li>
- Azure deploys SQL Server and Database<\/li>
- Done!<\/li><\/ol>
Total time: about 8 minutes.<\/p>
My Mistakes and Fixes<\/h3>Mistake 1: Forgot to Make Container Public<\/h3>
I created the container but forgot –public-access blob.<\/p>
Error:<\/p>
Failed to download template\nStatus code: 404<\/code><\/pre>Azure couldn’t download my template because it was private!<\/p>
Fix:<\/p>
az storage container set-permission \\\n --name template \\\n --account-name rezatemplate9473 \\\n --public-access blob<\/code><\/pre>Mistake 2: Wrong URL<\/h3>
I typed the URL wrong in my main template:<\/p>
\"uri\": \"https:\/\/rezatemplate9473.blob.core.windows.net\/template\/sqldatabase.json\"\n\/\/ I forgot the \"03-\" at the start!<\/code><\/pre>Fix: Copy the exact URL from Azure CLI:<\/p>
az storage blob url \\\n --account-name rezatemplate9473 \\\n --container-name template \\\n --name 03-sqldatabase.json<\/code><\/pre>Then paste it carefully!<\/p>
Mistake 3: Used “Complete” Mode<\/h3>
First time I wrote:<\/p>
\"mode\": \"Complete\"<\/code><\/pre>This is dangerous! “Complete” mode deletes resources that are NOT in the template.<\/p>
I had a storage account in my resource group. When I deployed with “Complete” mode, Azure deleted my storage account!<\/p>
Fix: Always use “Incremental” mode:<\/p>
\"mode\": \"Incremental\"<\/code><\/pre>Mistake 4: Parameter Names Don’t Match<\/h3>
In my template:<\/p>
\"parameters\": {\n \"SQLLogin\": { \/\/ Capital L<\/code><\/pre>In my parameter file:<\/p>
\"parameters\": {\n \"sqlLogin\": { \/\/ lowercase l<\/code><\/pre>Error:<\/p>
Template parameter 'SQLLogin' is not provided<\/code><\/pre>Parameter names are case-sensitive! They must match exactly.<\/p>
Fix: Use the same name everywhere.<\/p>
Why Linked Templates Are Good<\/h3>
After I started using linked templates, I learned these benefits:<\/p>
1. I Can Reuse Code<\/h3>
I created one SQL template. Now I use it in 5 projects:<\/p>
- Project A: Web App + SQL<\/li>
- Project B: VM + SQL<\/li>
- Project C: Function App + SQL<\/li><\/ul>
Same SQL code everywhere! I don’t copy-paste anymore.<\/p>
2. Easy to Fix Bugs<\/h3>
I found a bug in my SQL template. I only need to fix it once:<\/p>
# Fix the template\nvim 03-sqldatabase.json\n\n# Upload new version\naz storage blob upload \\\n --account-name rezatemplate9473 \\\n --container-name template \\\n --name 03-sqldatabase.json \\\n --file 03-sqldatabase.json \\\n --overwrite<\/code><\/pre>Done! All 5 projects get the fix on next deployment.<\/p>
3. Smaller Files<\/h3>
Before: One file with 500 lines – hard to read!<\/p>
After:<\/p>
- Main file: 50 lines<\/li>
- SQL file: 80 lines<\/li>
- Network file: 100 lines<\/li><\/ul>
Each file is small and easy to understand.<\/p>
4. Team Can Share<\/h3>
My team has different people:<\/p>
- Network expert makes network templates<\/li>
- Database expert makes SQL templates<\/li>
- I make Web App templates<\/li><\/ul>
We share templates! I use their templates in my projects.<\/p>
5. Easy to Test<\/h3>
I can test each template separately:<\/p>
# Test only SQL template\naz deployment group create \\\n --resource-group test-rg \\\n --template-uri \"https:\/\/rezatemplate9473.blob.core.windows.net\/template\/03-sqldatabase.json\" \\\n --parameters SQLLogin=test SQLPassword='Test@123'<\/code><\/pre>If SQL template works alone, then it will work in my main template too!<\/p>
Two Ways to Pass Parameters<\/h3>
I showed you parametersLink (parameter file URL). But there’s another way!<\/p>
Way 1: Use Parameter File (What I Showed)<\/h3>{\n \"type\": \"Microsoft.Resources\/deployments\",\n \"name\": \"LinkedTemplate\",\n \"properties\": {\n \"mode\": \"Incremental\",\n \"templateLink\": {\n \"uri\": \"https:\/\/...\/template.json\"\n },\n \"parametersLink\": {\n \"uri\": \"https:\/\/...\/parameters.json\"\n }\n }\n}<\/code><\/pre>Good for: Many parameters, reusing parameters<\/p>
Way 2: Write Parameters Inline<\/h3>{\n \"type\": \"Microsoft.Resources\/deployments\",\n \"name\": \"LinkedTemplate\",\n \"properties\": {\n \"mode\": \"Incremental\",\n \"templateLink\": {\n \"uri\": \"https:\/\/...\/template.json\"\n },\n \"parameters\": {\n \"SQLLogin\": {\n \"value\": \"sqlusr\"\n },\n \"SQLPassword\": {\n \"value\": \"Azure@123\"\n }\n }\n }\n}<\/code><\/pre>Good for: Few parameters, passing values from main template<\/p>
Both ways work! Choose what you like.<\/p>
Linked vs Nested Templates<\/h3>
Some people talk about “nested templates”. What’s the difference?<\/p>
Linked Template (what I use):<\/p>
- Template file is at a URL (like blob storage)<\/li>
- You can use it many times<\/li>
- Easy to share with team<\/li><\/ul>
\"templateLink\": {\n \"uri\": \"https:\/\/...\/template.json\" \/\/ External file\n}<\/code><\/pre>Nested Template:<\/p>
- Template code is inside the main template<\/li>
- All code in one file<\/li>
- Cannot reuse easily<\/li><\/ul>
\"template\": { \/\/ Code directly here\n \"$schema\": \"...\",\n \"resources\": [...]\n}<\/code><\/pre>I prefer Linked Templates because:<\/p>
- Easier to read<\/li>
- Can test separately<\/li>
- Can reuse in many projects<\/li>
- Team can share templates<\/li><\/ul>
Simple Security Tips<\/h3>
My setup uses public blob access. This is OK for learning. But for production (real work), do this:<\/p>
1. Use SAS Token<\/h3>
SAS token = Special URL that expires after some time.<\/p>
# Create token that works for 1 year\nEXPIRY=$(date -u -d \"1 year\" '+%Y-%m-%dT%H:%MZ')\n\nSAS_TOKEN=$(az storage container generate-sas \\\n --account-name rezatemplate9473 \\\n --name template \\\n --permissions r \\\n --expiry $EXPIRY \\\n --output tsv)<\/code><\/pre>Then use URL with token:<\/p>
https:\/\/rezatemplate9473.blob.core.windows.net\/template\/03-sqldatabase.json?sp=r&st=...<\/code><\/pre>2. Don’t Put Passwords in Git<\/h3>
Bad:<\/p>
\/\/ parameters.json in Git\n{\n \"SQLPassword\": {\n \"value\": \"Azure@123\" \/\/ Everyone can see this!\n }\n}<\/code><\/pre>Good: Pass password when deploying:<\/p>
az deployment group create \\\n --template-file main.json \\\n --parameters SQLPassword='SecretPassword123!'<\/code><\/pre>Or use Azure Key Vault for secrets.<\/p>
What I Learned<\/h3>- Linked templates help reuse code – Write once, use many times<\/li>
- Blob storage is easy – Just upload files and use URL<\/li>
- Always use Incremental mode – Complete mode is dangerous<\/li>
- Public access is OK for learning – But use SAS tokens for production<\/li>
- Parameter files are separate – Template has logic, parameters have values<\/li>
- Test templates separately – Makes debugging easier<\/li>
- Team can share templates – Everyone benefits<\/li><\/ol>","protected":false},"excerpt":{"rendered":"
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