NSSM

What NSSM does

NSSM is a service helper program similar to srvany and cygrunsrv, but with the features a real service manager needs. It can start any application as an NT service and will restart the service if it fails for any reason.

About this fork

NSSM was originally written by Iain Patterson and released into the public domain; the original site is nssm.cc. Its last release (2.24) dates from 2017. This is a maintained continuation with the following changes, and it remains 100% compatible with the original command syntax and registry layout.

Quick start

All commands require an administrator command prompt. In the examples below we install a Node.js application as a service named myapp — substitute your own paths.

1. Install the service

   The quickest way — pass everything on the command line:

   nssm install myapp "C:\apps\node\node.exe" "C:\apps\myapp\server.js"

   Or run nssm install myapp without an application path to open the GUI installer. Paths containing spaces must be quoted.

2. Tune the essentials

   rem Where the application starts
   nssm set myapp AppDirectory C:\apps\myapp
   
   rem Log stdout and stderr to files
   nssm set myapp AppStdout C:\logs\myapp.out.log
   nssm set myapp AppStderr C:\logs\myapp.err.log
   
   rem Rotate logs at 10 MB and prefix each line with a timestamp
   nssm set myapp AppRotateFiles 1
   nssm set myapp AppRotateBytes 10485760
   nssm set myapp AppTimestampLog 1
   
   rem Show the service as "My Application" with a description
   nssm set myapp DisplayName "My Application"
   nssm set myapp Description "My web application server"

3. Start it

   nssm start myapp

   Check that it is running:

   nssm status myapp
   nssm processes myapp

4. Manage it day to day

   nssm restart myapp
   nssm stop myapp
   nssm list

   You can also control the service with services.msc or sc.exe — NSSM services are ordinary Windows services.

5. Back it up or move it

   nssm dump myapp

   Prints a batch script which recreates the service. Run the output on another machine (after copying nssm.exe there) to clone the service. nssm dump myapp myapp2 shows myapp's configuration but writes commands for a service named myapp2.

6. Remove it

   nssm remove myapp confirm

   NSSM stops the service first, then deletes it. No reboot needed even if the service was running.

Command reference

Everywhere <servicename> appears you may substitute the service's display name as well as its key name. Run nssm with no arguments to see built-in usage.

Configuration reference

All settings live in the registry under HKLM\SYSTEM\CurrentControlSet\Services\<service>\Parameters and are managed with nssm get / nssm set / nssm reset. Parameter names on the command line are the same as the registry value names below.

Application

Process control

I/O redirection

Log rotation

Exit actions

NSSM reads AppExit values named after the application's exit code, falling back to the default value. Check the Windows event log to find the exit code. Configure per code with nssm set <svc> AppExit <code> <action> or the default with nssm set <svc> AppExit Default <action>.

Stopping the application

When a service stops, NSSM tries four methods in order, each with a default 1500 ms timeout, applying them to the whole process tree:

1. Generate a Control-C event on the application's console.
2. Post WM_CLOSE to the application's windows.
3. Post WM_QUIT to the application's threads.
4. Call TerminateProcess().

Environment variables

Entries are KEY=VALUE pairs; variables are expanded in order, so PATH=C:\bin;%PATH% works in AppEnvironmentExtra. On the command line each pair is a separate argument, and +KEY=VALUE / -KEY add/remove single variables:

nssm set myapp AppEnvironmentExtra JAVA_HOME=C:\jdk-17
nssm set myapp AppEnvironmentExtra +PATH=C:\apps\myapp\bin
nssm set myapp AppEnvironmentExtra -JAVA_HOME

System service settings

These correspond to standard service registry values and can also be read or written for non-NSSM services:

Event hooks

NSSM can run your own commands in response to service events. Configure a hook with nssm set <servicename> AppEvents <event>/<action> <command> or set the registry string value Parameters\AppEvents\<event>\<action> directly.

Hooks run with the service's environment plus context variables such as %NSSM_EXE%, %NSSM_SERVICE_NAME%, %NSSM_EVENT%, %NSSM_EXITCODE% and many more; check %NSSM_HOOK_VERSION% before using them. Example — restart the service when the system resumes:

nssm set myapp AppEvents Power/Resume "%NSSM_EXE% restart %NSSM_SERVICE_NAME%"

FAQ & troubleshooting