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PM2 accepts environment variables in two practical ways: assign them inline when you start or update an app, or define them in an ecosystem file. Your Node.js code reads either method through process.env. For a one-off launch, use NAME=value pm2 start app.js. For repeatable deployments and separate development, staging and production values, use env and named env_* blocks in an ecosystem file.
The important update rule is easy to miss: a changed inline shell value is not automatically copied into an already managed process. Restart or reload with --update-env. Values changed in an ecosystem file are applied when you restart or reload the app.
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PM2 starts your Node.js process with an environment inherited from the command that launches it or from the configuration in an ecosystem file. In application code, access a value by its exact name:
const endpoint = process.env.API_URL;Choose the method according to how often the value changes and whether more than one environment must be reproducible.
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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 the command is scripted |
Ecosystem env |
Shared defaults and checked-in app configuration | Use an env_<name> block with --env <name> |
Restart or reload after editing the file | High |
| External secret or platform injection | Secrets and infrastructure-managed configuration | Controlled outside the app file | Depends on how the host exports values; PM2 receives the resulting process environment | Medium to high |
The third row is an operational pattern rather than a separate PM2 configuration feature. A deployment system or host exports the variables, and PM2 starts the process with those values.
Pass variables on a one-off PM2 start
Start an app with an inline assignment
Put the assignment immediately before the PM2 command:
ENV_VAR=value pm2 start app.jsFor example:
API_URL=https://api.example.com pm2 start app.jsPM2 starts app.js with API_URL available to the Node.js process. Read it in the application as process.env.API_URL:
const apiUrl = process.env.API_URL;This style is useful for a temporary test, a manual launch, or a quick override when you do not need a checked-in configuration file. It is less suitable as the main deployment record because the values live in shell history, deployment scripts or operator notes rather than in one PM2 application definition.
Use more than one variable
Place each assignment before the command, separated by spaces:
NODE_ENV=production API_URL=https://api.example.com pm2 start app.jsThe application receives both names. Names are case-sensitive, so API_URL and api_url are different variables. Keep the spelling in the shell command, application code and any ecosystem file identical.
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PM2 deliberately treats environment inherited from the CLI conservatively. If an app is already managed and you run a new command with a different value, the process can continue using the old value. Apply the changed value during a restart or reload with --update-env:
ENV_VAR=somethingnew pm2 restart app --update-envUse the same pattern for a reload:
ENV_VAR=somethingnew pm2 reload app --update-envThe option matters because restarting without it may leave the managed process with the environment it already held. PM2 documentation describes this behavior as conservative: newly supplied CLI variables are not updated into the application during a normal restart, reload, stop or start unless you request the environment update.
Use an ecosystem file for repeatable configuration
Create the configuration
An ecosystem file gathers the PM2 options and environment variables for one or more applications. A minimal file named ecosystem.config.js can define a default environment and a production environment:
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 injected into the application. The env_production object is a named alternative. PM2 merges the selected configuration into the process environment when it starts the app.
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Start the default block
Run:
pm2 start ecosystem.config.jsThis starts the app using the values in env. In the example, the process receives NODE_ENV=development and the local API URL.
Select a named environment
Choose the production block with:
pm2 start ecosystem.config.js --env productionThe selector name must match the suffix exactly: --env production selects env_production. A staging setup follows the same convention:
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"
}
}]
};With this arrangement, the environment name is explicit in the command and the values remain reviewable in one file. Add a new block only when that environment has a distinct, intentional configuration.
Manage several applications in one file
The apps array can contain multiple application definitions. Give each a distinct name and the correct script. When a file declares several apps, select the intended one with PM2’s --only option from the ecosystem-file workflow. This prevents an environment change intended for one service from being applied to every service in the file.
How environment changes are applied
Changes made in an ecosystem file
Edit the relevant env or env_* object, then restart or reload the app managed from that ecosystem file. PM2 states that ecosystem-file environment values are updated on pm2 restart or pm2 reload.
For example, changing API_URL in env_production does not alter a process that is currently running until that process is restarted or reloaded. Make sure you edit the same ecosystem file and app definition that PM2 is using.
Changes supplied by the shell
For CLI assignments, include --update-env on the restart or reload command. The assignment and option belong on the same command so PM2 can import the new value:
API_URL=https://new-api.example.com pm2 restart my-node-app --update-envWithout the option, checking the shell variable alone does not prove that the already managed Node.js process changed.
Configure production and staging safely
Keep selectors and block names aligned
PM2 uses the text after --env to find a block named env_ plus that text. These pairs align:
env_productionwith--env productionenv_stagingwith--env staging
A spelling or capitalization mismatch means PM2 cannot select the intended block. Treat the suffix as an exact identifier, not a descriptive label.
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Separate defaults from deployable environments
Use env for the default developers should receive when no selector is supplied. Put staging and production endpoints in their named blocks so a plain start does not silently point at a remote service. Give each block a complete, deliberate set of values rather than relying on an operator to remember an additional shell assignment.
Switch deliberately
Before starting or restarting for a deployment, verify three things:
- The ecosystem file path is the intended one.
- The application name and script identify the intended service.
- The selector exactly matches the desired
env_*block.
Then use the PM2 start or restart/reload workflow for that app. If several applications share a file, use --only when the operation should affect just one of them.
Read and validate variables in Node.js
Access the injected value
Read a variable through process.env at the point where your application needs it:
const apiUrl = process.env.API_URL;
console.log(`Using API endpoint: ${apiUrl}`);The variable name must match the PM2 configuration exactly. A typo in either place results in a missing value from the application’s perspective.
Remember that environment values arrive as strings
Environment variables are represented as text. If application logic needs a number or a boolean, convert and validate it in your startup configuration rather than assuming JavaScript has already performed the conversion. Keep the original key name in the PM2 command or ecosystem object, and make the conversion decision in one clearly documented place in the application.
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Fail clearly when a required value is absent
For values the app cannot operate without, validate them during startup instead of allowing an obscure downstream error:
function requireEnv(name) {
const value = process.env[name];
if (!value) {
throw new Error(`Missing required environment variable: ${name}`);
}
return value;
}
const apiUrl = requireEnv("API_URL");This validation is an application-level safeguard. PM2 injects the environment; it does not decide which variables are mandatory for your business logic. A clear startup error also tells you whether the issue is configuration rather than an API connection or routing failure.
Verify the selected configuration without exposing secrets
When diagnosing a deployment, log the names of non-sensitive settings or a deliberately safe value such as the selected environment and endpoint host. Do not print passwords, tokens or complete credential values into application logs. A startup check that reports a missing key, while redacting its value, is more useful than dumping the entire environment.
Do not assume PM2 loads a .env file
PM2’s documented mechanisms here are inline CLI assignments and ecosystem-file blocks. Do not assume that placing a file named .env beside your application automatically populates process.env under PM2. If your project uses a separate environment-file loader or a Node.js runtime option, configure that mechanism explicitly and verify it independently. Otherwise, define the values in the ecosystem file or inject them from the host before PM2 starts the process.
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Keep secrets out of committed configuration
An ecosystem file is convenient for repeatable non-secret settings such as NODE_ENV and an endpoint. Plaintext production credentials in a public repository create a separate operational risk. Use the deployment platform or host’s secret-management process to export sensitive values at runtime, then start PM2 with that environment.
This pattern does not mean PM2 encrypts ecosystem files. PM2 receives whatever the launching environment provides. Protect the source of the variables, access to the host and any deployment logs or scripts that might expose them. Keep only safe defaults and non-sensitive routing information in a file that is intended to be reviewed or committed.
A deployment sequence that avoids stale configuration
For a repeatable release, first identify the exact ecosystem file and app name that represent the service. Review the intended env_* block, confirm its selector, and check that secrets will be exported by the host or deployment system rather than copied into source control. Start with pm2 start ecosystem.config.js --env production for a new process, or restart/reload the named app after an edit. If the value came from a shell assignment instead of the file, include --update-env on that same restart or reload command.
After the operation, let the application perform its startup validation. A missing-key error points to injection, naming or block selection; an application-level connection error means the value was present but may point to the wrong service. This separation makes rollback and incident diagnosis more predictable without requiring the application to print sensitive values.
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process.env is undefined
- Confirm the variable name in application code exactly matches the CLI assignment or ecosystem key.
- Confirm PM2 started the intended script, not a different entry point.
- If using an ecosystem file, verify that you started that file and selected the expected block.
- Restart or reload after changing the configuration.
For a required setting, startup validation should produce the missing variable’s name, making a spelling or selection error easier to locate.
The old value remains after a CLI change
Use the changed assignment together with --update-env:
NEW_VALUE=updated pm2 restart my-node-app --update-envA normal restart without the option can preserve the environment already held by PM2’s managed process.
The production value is not being selected
Check that the file contains env_production and that the command uses --env production. The suffix must match exactly. If you intended staging, use env_staging and --env staging instead.
An ecosystem edit has no effect
Restart or reload the app after saving the file. Then verify that the command references the edited ecosystem file and the correct app. When multiple apps are declared, use --only to target the service you changed.
A secret appears in source control
Remove the plaintext value from the committed configuration, rotate the exposed credential through the relevant service, and move injection to the host or deployment platform’s secret process. Keep the PM2 file limited to values that are safe for the repository’s audience.
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Practical choices and common pitfalls
Inline assignments are fast but easy to lose: a later operator may not know which shell command originally supplied the value, and shell history or deployment logs can retain sensitive text. Ecosystem files make the selected environment and endpoint visible for review, but they must be protected when they contain anything confidential. Host-managed injection keeps secrets outside the application definition, yet the deployment process must reliably export those values before PM2 starts or updates the app.
Do not mix methods accidentally. For example, an operator may edit env_production while a running process was originally started with a CLI override. Decide which source is authoritative, then restart or reload using that source. Similarly, changing a file on disk is not the same as changing a running process; the process receives its environment at startup or update time.
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When several services share one ecosystem file, confirm both the app selector and the environment selector. A correct production block applied to the wrong script is still an outage. Keep names distinct, use --only for a single service, and make startup validation part of every service so configuration mistakes fail early.
A practical operating checklist
- Choose inline CLI assignment for a temporary or one-off launch; choose an ecosystem file for repeatable operation.
- Use the exact variable name your Node.js code reads through
process.env. - For multiple environments, create blocks such as
env_stagingandenv_production. - Select a block with
--env <name>, matching the suffix exactly. - After a CLI value changes, restart or reload with
--update-env. - After an ecosystem value changes, restart or reload the affected app.
- Check the ecosystem path, script, app name and, when needed,
--only. - Validate required variables during application startup.
- Inject production secrets through the host or deployment platform rather than committing plaintext credentials.
- Do not rely on automatic
.envparsing unless you have separately configured a loader or Node.js runtime option.
What to remember
For a quick start, write NAME=value pm2 start app.js and read the result as process.env.NAME. For a durable setup, put defaults in env and environment-specific values in blocks such as env_production, then select one with --env production. The update behavior determines whether your change is visible: CLI assignments require --update-env on restart or reload, while ecosystem-file edits take effect when the app is restarted or reloaded. Explicit validation and deliberate secret injection turn those mechanics into a reliable deployment process.
Frequently Asked Questions
How do I pass an environment variable when starting a Node.js app with PM2?
Put the assignment before the command, for example API_URL=https://api.example.com pm2 start app.js. Read it in Node.js as process.env.API_URL.
Why did PM2 keep my old value after I changed the shell variable?
CLI-provided environment is conservative. Restart or reload with the new assignment and --update-env, such as API_URL=https://new-api.example.com pm2 restart my-node-app --update-env.
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesHow do I configure production and staging values?
Define env_staging and env_production objects in an ecosystem file, then run with --env staging or --env production. The suffix must match exactly.
Do ecosystem-file changes apply immediately?
No. Save the edited file, then restart or reload the affected PM2 app. PM2 applies the updated environment during that operation.
Why is process.env.MY_VARIABLE undefined?
Check spelling and capitalization, the script PM2 started, the ecosystem-file path, and the selected environment block. Restart or reload after correcting the configuration.
Does PM2 automatically load a .env file?
Do not assume so. Use an explicitly configured environment-file loader or Node runtime option, or define the values in the ecosystem file or host environment.
Where should production secrets be stored?
Keep plaintext credentials out of committed ecosystem files. Have the deployment platform or host’s secret process export them at runtime before PM2 starts or updates the app.
How can I update only one app in a shared ecosystem file?
Give each app a distinct name and use PM2’s --only option to target the intended service.
The Bottom Line
Use NAME=value pm2 start app.js for a one-off launch, and use an ecosystem file with env plus env_* blocks for repeatable staging and production configuration. Apply changed CLI values with --update-env; restart or reload after ecosystem edits. Validate required keys in Node.js and inject secrets from the host or deployment platform instead of committing them.
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