PM2 accepts environment variables in two documented ways: assign them inline when starting or restarting an app, or define them in an ecosystem configuration file. Your Node.js code reads either form through process.env. For a changed inline value to reach an existing PM2 process, restart or reload with --update-env. For an ecosystem file, restart or reload after editing the file; PM2 applies the updated values then.
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- One-off start:
ENV_VAR=value pm2 start app.js - Repeatable configuration: an ecosystem file with
envand optionalenv_production,env_staging, or other named blocks - Environment selection:
pm2 start ecosystem.config.js --env production
How PM2 environment variables reach your Node.js app
When PM2 launches a Node.js process, it gives that process an environment inherited from the command that started it and from the PM2 configuration. Node exposes those values as strings on the global process.env object. A variable named API_URL is therefore read in application code as process.env.API_URL.
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PM2’s two supported configuration patterns solve different operational problems. An inline assignment is convenient for a quick start or a temporary override. An ecosystem file makes the intended environment explicit, repeatable, and easier to use when several applications or deployment stages are involved.
Read the value in application code
const apiUrl = process.env.API_URL;
console.log('API URL:', apiUrl);Environment values arrive as text. If your code needs a number or a boolean, convert and validate it deliberately instead of relying on JavaScript truthiness:
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const port = Number.parseInt(process.env.PORT ?? '', 10);
const debug = process.env.DEBUG === 'true';
if (!Number.isInteger(port)) {
throw new Error('PORT must be an integer');
}For required settings, fail during startup with a useful message. A process that starts with an undefined database URL can produce a much less actionable error later, after handling traffic.
function required(name) {
const value = process.env[name];
if (!value) {
throw new Error(`Missing required environment variable: ${name}`);
}
return value;
}
const databaseUrl = required('DATABASE_URL');Method 1: pass a variable on the PM2 command line
Prefix the PM2 command with a shell assignment:
ENV_VAR=value pm2 start app.jsFor example:
API_URL=https://api.example.com NODE_ENV=production pm2 start app.js --name my-node-appPM2 starts the application with both values, and the code can access them as process.env.API_URL and process.env.NODE_ENV. This approach is useful when you are testing a value, performing a one-off launch, or wrapping PM2 in a deployment script that already exports the deployment context.
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Quoting values safely
Use shell quoting when a value contains spaces or characters interpreted by the shell:
GREETING='Hello from production' pm2 start app.jsDo not put an unquoted value containing spaces after the equals sign; the shell will treat the remaining words as separate arguments. Values containing shell metacharacters require particularly careful quoting, and secrets should not be exposed in command history or process listings when your host’s operational policy prohibits that.
Update an existing process after an inline change
PM2 keeps the environment associated with a managed process. If you run a new command with a different assignment, an already-running application does not automatically receive the changed value. Include --update-env when restarting or reloading:
ENV_VAR=somethingnew pm2 restart my-node-app --update-envThe same flag applies to a reload:
API_URL=https://new-api.example.com pm2 reload my-node-app --update-envWithout the flag, the process can continue using the older value even though the shell command contains the new one. This conservative behavior is documented by PM2 for CLI-provided environment variables.
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- Starting a local test with a temporary setting.
- Applying a deployment value supplied by a shell script or host-level service.
- Overriding one setting for a controlled restart without changing a shared configuration file.
Inline assignments are less suitable as the only record of a production configuration: they are easy to mistype, hard to review, and inconvenient when you maintain development, staging, and production variants.
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Method 2: define variables in an ecosystem file
An ecosystem file gathers PM2 options and environment variables for one or more applications. Create a file such as ecosystem.config.js beside the project:
module.exports = {
apps: [{
name: "my-node-app",
script: "./app.js",
env: {
NODE_ENV: "development",
API_URL: "http://localhost:3000"
},
env_production: {
NODE_ENV: "production",
API_URL: "https://api.example.com"
}
}]
};The env object is the default set of variables injected into the application. Named objects whose keys begin with env_ provide alternatives. In the example, env_production is selected with the name production.
Start the default environment
pm2 start ecosystem.config.jsThis starts the application using the values in the env block.
Start a named environment
pm2 start ecosystem.config.js --env productionThe selector after --env must match the suffix exactly. Therefore --env production selects env_production, while --env staging would select env_staging if that block exists.
Add a staging block
module.exports = {
apps: [{
name: "my-node-app",
script: "./app.js",
env: {
NODE_ENV: "development",
API_URL: "http://localhost:3000"
},
env_staging: {
NODE_ENV: "staging",
API_URL: "https://staging-api.example.com"
},
env_production: {
NODE_ENV: "production",
API_URL: "https://api.example.com"
}
}]
};Launch staging with:
pm2 start ecosystem.config.js --env stagingKeep the block names and command selectors consistent. A typo such as env_stage paired with --env staging will not select the block you intended.
Select one application from a multi-app file
An ecosystem file can declare several applications. When you need to operate on only one declaration, use PM2’s --only option with the application name:
pm2 start ecosystem.config.js --only my-node-app --env productionThis avoids accidentally starting or restarting every application described in the file.
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Applying edits to an ecosystem file
After changing an ecosystem file, restart or reload the application so PM2 launches workers with the new values:
pm2 restart ecosystem.config.js --env productionpm2 reload ecosystem.config.js --env productionPM2 documents that ecosystem-file environment changes are applied on pm2 restart or pm2 reload. Editing the JavaScript file alone does not mutate the environment of a process that is already running.
If the file contains multiple applications, target the intended one:
pm2 restart ecosystem.config.js --only my-node-app --env productionUse the same file path and application name that you used when starting the process. Running a command from another directory, or pointing at a second ecosystem file with a similar name, can make a correct edit appear ineffective.
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| Method | Best for | Environment switching | Updating a running app | Repeatability |
|---|---|---|---|---|
Inline CLI (NAME=value pm2 start) |
One-off starts or quick overrides | Controlled by the shell command | Restart or reload with --update-env |
Low unless scripted |
Ecosystem env and env_* |
Shared defaults and checked-in app configuration | env_<name> with --env <name> |
Restart or reload after editing the file | High |
| External secret or platform injection | Secrets and infrastructure-managed configuration | Controlled outside the application file | Depends on how the host exports values; PM2 receives the resulting process environment | Medium to high |
The first two rows are PM2 configuration mechanisms. External injection is an operational pattern: a deployment system or host secret store supplies variables before PM2 starts or reloads the process. PM2 does not turn that pattern into encrypted storage.
Using production and staging safely
Separate environment blocks make it harder to point a staging build at a production service by accident. Give each block complete, explicit values for settings that differ between environments:
module.exports = {
apps: [{
name: "orders-api",
script: "./server.js",
env_staging: {
NODE_ENV: "staging",
API_URL: "https://staging-api.example.com",
LOG_LEVEL: "debug"
},
env_production: {
NODE_ENV: "production",
API_URL: "https://api.example.com",
LOG_LEVEL: "info"
}
}]
};- Verify the ecosystem file path and the application name.
- Choose the block with
--env stagingor--env production. - Restart or reload after every configuration edit.
- Check application startup logs for the environment-specific behavior you expect.
Do not log full credentials or tokens while diagnosing an environment problem. If you need proof that a value is present, log a non-sensitive property such as whether it is defined, or log a redacted endpoint without query parameters and credentials.
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Secrets, source control, and runtime injection
Plaintext production secrets in a repository can be copied by anyone who can read the repository, its history, backups, or build artifacts. Treat passwords, private keys, API tokens, and connection strings as secrets rather than ordinary application settings.
- Keep secret values in the deployment platform or host’s secret-management process.
- Inject them into the environment at runtime, then start or reload PM2.
- Commit non-sensitive defaults and documented variable names, not production credentials.
- Review shell history, CI logs, and startup output for accidental secret disclosure.
An ecosystem file can still describe non-secret values such as NODE_ENV or a public API endpoint. If a secret must be referenced by that file, arrange for the host or deployment process to provide it without committing the secret itself. The exact injection mechanism depends on your infrastructure; PM2 simply receives the environment that exists when it launches the process.
Why process.env is undefined under PM2
“Undefined” can mean either that the variable was never supplied or that the application is reading a different name than the one you configured. Work through these checks in order.
Check the spelling and case
Environment names are case-sensitive on common Unix-like systems. API_URL, Api_Url, and api_url are different names. Compare the exact key in the command or ecosystem block with the key in process.env.
Confirm the command actually supplied the value
For an inline start, the assignment must appear before the PM2 command:
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API_URL=https://api.example.com pm2 start app.jsWriting pm2 start app.js API_URL=... does not create the same shell environment assignment. If a wrapper script is involved, make sure it exports the variable before invoking PM2.
Confirm the selected ecosystem block
pm2 start ecosystem.config.js uses the default env block. It does not select env_production automatically. Use --env production, and ensure the object is named exactly env_production.
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Restart after changing configuration
A running process keeps the environment with which it was launched. Use pm2 restart or pm2 reload after an ecosystem edit. For an inline change, include --update-env on that restart or reload.
Verify the file and app entry point
When several projects or ecosystem files are present, you may be editing one declaration while PM2 is running another. Confirm the script path, current working directory, ecosystem filename, and application name. Use --only when a file defines multiple apps.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchRemember that PM2 does not automatically parse every .env file
Putting API_URL=... in a file named .env does not, by itself, make PM2 load it. A separate environment-file loader or a Node runtime option must be configured for that behavior. Without such a setup, use the PM2 CLI assignment, an ecosystem env block, or your host’s runtime injection process.
A repeatable deployment workflow
The following workflow keeps configuration changes understandable and minimizes stale-process mistakes.
- Declare the variable contract. List required names such as
DATABASE_URL,API_URL, andPORT. Decide which are public configuration and which are secrets. - Validate at startup. Read required values through
process.envand throw a clear error when one is absent or malformed. - Choose the source. Use an inline assignment for a one-off operation, an ecosystem file for repeatable environment blocks, or host-managed injection for secrets.
- Start the intended app. Use the exact ecosystem path, script path, and application name. Add
--env productionor another selector when needed. - Change values deliberately. Edit the ecosystem block or update the host’s exported environment. Do not assume a changed shell value alters an already-running process.
- Restart or reload. Add
--update-envwhen the new value comes from a CLI assignment. A changed ecosystem file is applied on restart or reload. - Inspect startup behavior. Check logs for the validation message or expected environment-specific configuration, while keeping secrets out of output.
Common failure modes and fixes
| Symptom | Likely cause | Fix |
|---|---|---|
process.env.MY_VARIABLE is undefined |
The name is misspelled, the variable was not supplied, or the wrong environment block was selected. | Compare names exactly, select the matching env_* block, and validate at startup. |
| A new CLI value is ignored | PM2 retained the environment of the existing process. | Restart or reload with the assignment and --update-env. |
| An ecosystem edit is ignored | The app was not restarted or the command targeted another file or app. | Restart or reload the edited file, verify its path, and use --only for a specific app. |
| Production settings are not active | --env production was omitted or the block suffix does not match. |
Use env_production with --env production. |
A .env file has no effect |
PM2 is not an automatic parser for arbitrary .env files. |
Configure a separate loader or Node runtime option, or provide values through PM2 or the host environment. |
| The app starts, then fails while handling requests | A required variable was missing or had an invalid type. | Parse and validate values during startup, with an error naming the missing variable. |
Practical command reference
# One-off start
API_URL=https://api.example.com pm2 start app.js --name my-node-app
# Update an existing process from the CLI
API_URL=https://new-api.example.com pm2 restart my-node-app --update-env
# Start the default ecosystem environment
pm2 start ecosystem.config.js
# Start a named environment
pm2 start ecosystem.config.js --env production
# Restart one app from a multi-app ecosystem file
pm2 restart ecosystem.config.js --only my-node-app --env production
# Reload after an ecosystem-file change
pm2 reload ecosystem.config.js --env productionWhat to remember
Use NAME=value pm2 start app.js for a quick, shell-controlled launch. Use an ecosystem file when configuration must be reviewable and when you need explicit development, staging, and production blocks. Read values with process.env.NAME, validate required settings before the server accepts traffic, and restart or reload after changes. Inline changes specifically require --update-env; ecosystem-file changes take effect on restart or reload. Keep production secrets in the host or deployment system and inject them at runtime rather than committing them to source control.
Frequently Asked Questions
Does PM2 automatically load a .env file?
No. A .env file has no effect merely because it exists. Configure a separate loader or Node runtime option, or provide the variables through PM2’s CLI, ecosystem configuration, or the host environment.
Why does my changed inline variable not appear after pm2 restart?
PM2 uses conservative handling for CLI-provided environment values. Put the new assignment on the restart or reload command and add –update-env.
How do I choose staging instead of production?
Define an env_staging block and run pm2 start ecosystem.config.js –env staging. The selector must match the suffix after env_.
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