The Non-Sucking Service Manager

Iain Patterson dee49fc1a0 Try to build PDB files even for releases. 7 years ago
.gitattributes c9c68980f3 Help git figure out how to diff .mc and .rc files. 8 years ago
ChangeLog.txt 32a1d0fab4 Set the environment before querying the registry. 9 years ago
README.txt caeb3c4a6f Fix lockup on with 64 cores. 7 years ago
account.cpp b76766ed76 Handle virtual accounts when dumping service config. 8 years ago
account.h b76766ed76 Handle virtual accounts when dumping service config. 8 years ago
console.cpp 897c7ad10b Support starting processes with a console on Windows 10. 7 years ago
console.h 800ca0c4f1 Added UTF-8 functions. 8 years ago
env.cpp 6456709797 Some notes on the environment and registry. 8 years ago
env.h f56089cede Added append_to/remove_from_environment_block(). 8 years ago
event.cpp e19b4a0eed Enough with the small buffers already. 10 years ago
event.h 8754d6de6c Be more Windowsy. 10 years ago
gui.cpp 54731dd901 Fixed buffer overflow in GUI browse(). 7 years ago
gui.h 2c60e5334f Allow editing services. 10 years ago
hook.cpp 2d1226f847 Don't leak hook startup handles. 7 years ago
hook.h b6f7fe3b11 Use CRLF consistently. 8 years ago
imports.cpp 2f3ab42db3 Use UTF-8 functions when working with explicit encodings. 8 years ago
imports.h 94d25a5dcf Use QueryFullProcessImageName() if available. 8 years ago
io.cpp 897c7ad10b Support starting processes with a console on Windows 10. 7 years ago
io.h ee9a86c840 Ensure logging threads exit. 7 years ago 9c88bc137c Added dump and processess commands to usage message. 7 years ago
nssm.cpp caeb3c4a6f Fix lockup on with 64 cores. 7 years ago
nssm.h ee9a86c840 Ensure logging threads exit. 7 years ago
nssm.ico d6ce7c473f New URL and icon. 12 years ago
nssm.rc 62f28c55d4 Tidy up French GUI. 7 years ago
nssm.sln 7b62a11307 Tidy up build directories. 10 years ago
nssm.vcproj dee49fc1a0 Try to build PDB files even for releases. 7 years ago
process.cpp 94d25a5dcf Use QueryFullProcessImageName() if available. 8 years ago
process.h 586ea54f69 Command to show processes started by the service. 8 years ago
registry.cpp cc956aacde Alow prefixing log output with a timestamp. 7 years ago
registry.h cc956aacde Alow prefixing log output with a timestamp. 7 years ago
resource.h cc956aacde Alow prefixing log output with a timestamp. 7 years ago
service.cpp 897c7ad10b Support starting processes with a console on Windows 10. 7 years ago
service.h a2f02c89be Command to exit with state code. 7 years ago
settings.cpp cc956aacde Alow prefixing log output with a timestamp. 7 years ago
settings.h 3c9d8f85d3 Command to dump service configuration. 8 years ago
utf8.cpp 291dfc8499 Use WideCharToMultiByte() correctly. 8 years ago
utf8.h 72ffbfb8a4 CRLF for utf8.* files. 8 years ago
version.cmd b2e2a895d7 Fixed year marker in build information. 10 years ago


NSSM: The Non-Sucking Service Manager
Version 2.24, 2014-08-31

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

NSSM also has a graphical service installer and remover.

Full documentation can be found online at

Since version 2.0, the GUI can be bypassed by entering all appropriate
options on the command line.

Since version 2.1, NSSM can be compiled for x64 platforms.
Thanks Benjamin Mayrargue.

Since version 2.2, NSSM can be configured to take different actions
based on the exit code of the managed application.

Since version 2.3, NSSM logs to the Windows event log more elegantly.

Since version 2.5, NSSM respects environment variables in its parameters.

Since version 2.8, NSSM tries harder to shut down the managed application
gracefully and throttles restart attempts if the application doesn't run
for a minimum amount of time.

Since version 2.11, NSSM respects srvany's AppEnvironment parameter.

Since version 2.13, NSSM is translated into French.
Thanks François-Régis Tardy.

Since version 2.15, NSSM is translated into Italian.
Thanks Riccardo Gusmeroli.

Since version 2.17, NSSM can try to shut down console applications by
simulating a Control-C keypress. If they have installed a handler routine
they can clean up and shut down gracefully on receipt of the event.

Since version 2.17, NSSM can redirect the managed application's I/O streams
to an arbitrary path.

Since version 2.18, NSSM can be configured to wait a user-specified amount
of time for the application to exit when shutting down.

Since version 2.19, many more service options can be configured with the
GUI installer as well as via the registry.

Since version 2.19, NSSM can add to the service's environment by setting
AppEnvironmentExtra in place of or in addition to the srvany-compatible

Since version 2.22, NSSM can set the managed application's process priority
and CPU affinity.

Since version 2.22, NSSM can apply an unconditional delay before restarting
an application which has exited.

Since version 2.22, NSSM can rotate existing output files when redirecting I/O.

Since version 2.22, NSSM can set service display name, description, startup
type, log on details and dependencies.

Since version 2.22, NSSM can manage existing services.

Since version 2.25, NSSM can execute commands in response to service events.

Since version 2.25, NSSM can list services it manages.

Since version 2.25, NSSM can dump the configuration of services it manages.

Since version 2.25, NSSM can show the processes managed by a service.

In the usage notes below, arguments to the program may be written in angle
brackets and/or square brackets. means you must insert the
appropriate string and [] means the string is optional. See the
examples below...

Note that everywhere appears you may substitute the
service's display name.

Installation using the GUI
To install a service, run

nssm install

You will be prompted to enter the full path to the application you wish
to run and any command line options to pass to that application.

Use the system service manager (services.msc) to control advanced service
properties such as startup method and desktop interaction. NSSM may
support these options at a later time...

Installation using the command line
To install a service, run

nssm install []

NSSM will then attempt to install a service which runs the named application
with the given options (if you specified any).

Don't forget to enclose paths in "quotes" if they contain spaces!

If you want to include quotes in the options you will need to """quote""" the

Managing the service
NSSM will launch the application listed in the registry when you send it a
start signal and will terminate it when you send a stop signal. So far, so
much like srvany. But NSSM is the Non-Sucking service manager and can take
action if/when the application dies.

With no configuration from you, NSSM will try to restart itself if it notices
that the application died but you didn't send it a stop signal. NSSM will
keep trying, pausing between each attempt, until the service is successfully
started or you send it a stop signal.

NSSM will pause an increasingly longer time between subsequent restart attempts
if the service fails to start in a timely manner, up to a maximum of four
minutes. This is so it does not consume an excessive amount of CPU time trying
to start a failed application over and over again. If you identify the cause
of the failure and don't want to wait you can use the Windows service console
(where the service will be shown in Paused state) to send a continue signal to
NSSM and it will retry within a few seconds.

By default, NSSM defines "a timely manner" to be within 1500 milliseconds.
You can change the threshold for the service by setting the number of
milliseconds as a REG_DWORD value in the registry at

Alternatively, NSSM can pause for a configurable amount of time before
attempting to restart the application even if it successfully ran for the
amount of time specified by AppThrottle. NSSM will consult the REG_DWORD value
at HKLM\SYSTEM\CurrentControlSet\Services\\Parameters\AppRestartDelay
for the number of milliseconds to wait before attempting a restart. If
AppRestartDelay is set and the application is determined to be subject to
throttling, NSSM will pause the service for whichever is longer of the
configured restart delay and the calculated throttle period.

If AppRestartDelay is missing or invalid, only throttling will be applied.

NSSM will look in the registry under
HKLM\SYSTEM\CurrentControlSet\Services\\Parameters\AppExit for
string (REG_EXPAND_SZ) values corresponding to the exit code of the application.
If the application exited with code 1, for instance, NSSM will look for a
string value under AppExit called "1" or, if it does not find it, will
fall back to the AppExit (Default) value. You can find out the exit code
for the application by consulting the system event log. NSSM will log the
exit code when the application exits.

Based on the data found in the registry, NSSM will take one of three actions:

If the value data is "Restart" NSSM will try to restart the application as
described above. This is its default behaviour.

If the value data is "Ignore" NSSM will not try to restart the application
but will continue running itself. This emulates the (usually undesirable)
behaviour of srvany. The Windows Services console would show the service
as still running even though the application has exited.

If the value data is "Exit" NSSM will exit gracefully. The Windows Services
console would show the service as stopped. If you wish to provide
finer-grained control over service recovery you should use this code and
edit the failure action manually. Please note that Windows versions prior
to Vista will not consider such an exit to be a failure. On older versions
of Windows you should use "Suicide" instead.

If the value data is "Suicide" NSSM will simulate a crash and exit without
informing the service manager. This option should only be used for
pre-Vista systems where you wish to apply a service recovery action. Note
that if the monitored application exits with code 0, NSSM will only honour a
request to suicide if you explicitly configure a registry key for exit code 0.
If only the default action is set to Suicide NSSM will instead exit gracefully.

Application priority
NSSM can set the priority class of the managed application. NSSM will look in
the registry under HKLM\SYSTEM\CurrentControlSet\Services\\Parameters
for the REG_DWORD entry AppPriority. Valid values correspond to arguments to
SetPriorityClass(). If AppPriority() is missing or invalid the
application will be launched with normal priority.

Processor affinity
NSSM can set the CPU affinity of the managed application. NSSM will look in
the registry under HKLM\SYSTEM\CurrentControlSet\Services\\Parameters
for the REG_SZ entry AppAffinity. It should specify a comma-separated listed
of zero-indexed processor IDs. A range of processors may optionally be
specified with a dash. No other characters are allowed in the string.

For example, to specify the first; second; third and fifth CPUs, an appropriate
AppAffinity would be 0-2,4.

If AppAffinity is missing or invalid, NSSM will not attempt to restrict the
application to specific CPUs.

Note that the 64-bit version of NSSM can configure a maximum of 64 CPUs in this
way and that the 32-bit version can configure a maxium of 32 CPUs even when
running on 64-bit Windows.

Stopping the service
When stopping a service NSSM will attempt several different methods of killing
the monitored application, each of which can be disabled if necessary.

First NSSM will attempt to generate a Control-C event and send it to the
application's console. Batch scripts or console applications may intercept
the event and shut themselves down gracefully. GUI applications do not have
consoles and will not respond to this method.

Secondly NSSM will enumerate all windows created by the application and send
them a WM_CLOSE message, requesting a graceful exit.

Thirdly NSSM will enumerate all threads created by the application and send
them a WM_QUIT message, requesting a graceful exit. Not all applications'
threads have message queues; those which do not will not respond to this

Finally NSSM will call TerminateProcess() to request that the operating
system forcibly terminate the application. TerminateProcess() cannot be
trapped or ignored, so in most circumstances the application will be killed.
However, there is no guarantee that it will have a chance to perform any
tidyup operations before it exits.

Any or all of the methods above may be disabled. NSSM will look for the
registry value which should be of type REG_DWORD set to a bit field describing
which methods should not be applied.

If AppStopMethodSkip includes 1, Control-C events will not be generated.
If AppStopMethodSkip includes 2, WM_CLOSE messages will not be posted.
If AppStopMethodSkip includes 4, WM_QUIT messages will not be posted.
If AppStopMethodSkip includes 8, TerminateProcess() will not be called.

If, for example, you knew that an application did not respond to Control-C
events and did not have a thread message queue, you could set AppStopMethodSkip
to 5 and NSSM would not attempt to use those methods to stop the application.

Take great care when including 8 in the value of AppStopMethodSkip. If NSSM
does not call TerminateProcess() it is possible that the application will not
exit when the service stops.

By default NSSM will allow processes 1500ms to respond to each of the methods
described above before proceeding to the next one. The timeout can be
configured on a per-method basis by creating REG_DWORD entries in the
registry under HKLM\SYSTEM\CurrentControlSet\Services\\Parameters.


Each value should be set to the number of milliseconds to wait. Please note
that the timeout applies to each process in the application's process tree,
so the actual time to shutdown may be longer than the sum of all configured
timeouts if the application spawns multiple subprocesses.

To skip applying the above stop methods to all processes in the application's
process tree, applying them only to the original application process, set the
registry value, which should be of type REG_DWORD, to 0.

Console window
By default, NSSM will create a console window so that applications which
are capable of reading user input can do so - subject to the service being
allowed to interact with the desktop.

Creation of the console can be suppressed by setting the integer (REG_DWORD)
registry value to 1.

I/O redirection
NSSM can redirect the managed application's I/O to any path capable of being
opened by CreateFile(). This enables, for example, capturing the log output
of an application which would otherwise only write to the console or accepting
input from a serial port.

NSSM will look in the registry under
HKLM\SYSTEM\CurrentControlSet\Services\\Parameters for the keys
corresponding to arguments to CreateFile(). All are optional. If no path is
given for a particular stream it will not be redirected. If a path is given
but any of the other values are omitted they will be receive sensible defaults.

AppStdin: Path to receive input.
AppStdout: Path to receive output.
AppStderr: Path to receive error output.

Parameters for CreateFile() are providing with the "AppStdinShareMode",
"AppStdinCreationDisposition" and "AppStdinFlagsAndAttributes" values (and
analogously for stdout and stderr).

In general, if you want the service to log its output, set AppStdout and
AppStderr to the same path, eg C:\Users\Public\service.log, and it should
work. Remember, however, that the path must be accessible to the user
running the service.

File rotation
When using I/O redirection, NSSM can rotate existing output files prior to
opening stdout and/or stderr. An existing file will be renamed with a
suffix based on the file's last write time, to millisecond precision. For
example, the file nssm.log might be rotated to nssm-20131221T113939.457.log.

NSSM will look in the registry under
HKLM\SYSTEM\CurrentControlSet\Services\\Parameters for REG_DWORD
entries which control how rotation happens.

If AppRotateFiles is missing or set to 0, rotation is disabled. Any non-zero
value enables rotation.

If AppRotateSeconds is non-zero, a file will not be rotated if its last write
time is less than the given number of seconds in the past.

If AppRotateBytes is non-zero, a file will not be rotated if it is smaller
than the given number of bytes. 64-bit file sizes can be handled by setting
a non-zero value of AppRotateBytesHigh.

If AppRotateDelay is non-zero, NSSM will pause for the given number of
milliseconds after rotation.

If AppStdoutCopyAndTruncate or AppStderrCopyAndTruncate are non-zero, the
stdout (or stderr respectively) file will be rotated by first taking a copy
of the file then truncating the original file to zero size. This allows
NSSM to rotate files which are held open by other processes, preventing the
usual MoveFile() from succeeding. Note that the copy process may take some
time if the file is large, and will temporarily consume twice as much disk
space as the original file. Note also that applications reading the log file
may not notice that the file size changed. Using this option in conjunction
with AppRotateDelay may help in that case.

Rotation is independent of the CreateFile() parameters used to open the files.
They will be rotated regardless of whether NSSM would otherwise have appended
or replaced them.

NSSM can also rotate files which hit the configured size threshold while the
service is running. Additionally, you can trigger an on-demand rotation by
running the command

nssm rotate

On-demand rotations will happen after the next line of data is read from
the managed application, regardless of the value of AppRotateBytes. Be aware
that if the application is not particularly verbose the rotation may not
happen for some time.

To enable online and on-demand rotation, set AppRotateOnline to a non-zero

Note that online rotation requires NSSM to intercept the application's I/O
and create the output files on its behalf. This is more complex and
error-prone than simply redirecting the I/O streams before launching the
application. Therefore online rotation is not enabled by default.

Timestamping output
When redirecting output, NSSM can prefix each line of output with a
millisecond-precision timestamp, for example:

2016-09-06 10:17:09.451 Pipeline main started

To enable timestamp prefixing, set AppTimestampLog to a non-zero value.

The prefix applies to both stdout and stderr. Prefixing requires
intercepting the application's I/O in the same way that online rotation
does. If log rotation and timestamp prefixing are both enabled, the
rotation will be online.

Environment variables
NSSM can replace or append to the managed application's environment. Two
multi-valued string (REG_MULTI_SZ) registry values are recognised under

AppEnvironment defines a list of environment variables which will override
the service's environment. AppEnvironmentExtra defines a list of
environment variables which will be added to the service's environment.

Each entry in the list should be of the form KEY=VALUE. It is possible to
omit the VALUE but the = symbol is mandatory.

Environment variables listed in both AppEnvironment and AppEnvironmentExtra
are subject to normal expansion, so it is possible, for example, to update the
system path by setting "PATH=C:\bin;%PATH%" in AppEnvironmentExtra. Variables
are expanded in the order in which they appear, so if you want to include the
value of one variable in another variable you should declare the dependency

Because variables defined in AppEnvironment override the existing
environment it is not possible to refer to any variables which were previously

For example, the following AppEnvironment block:


Would result in a PATH of "C:\bin;C:\Windows\System32;C:\Windows" as expected.

Whereas the following AppEnvironment block:


Would result in a path containing only C:\bin and probably cause the
application to fail to start.

Most people will want to use AppEnvironmentExtra exclusively. srvany only
supports AppEnvironment.

As of version 2.25, NSSM parses AppEnvironment and AppEnvironmentExtra
itself, before reading any other registry values. As a result it is now
possible to refer to custom environment variables in Application,
AppDirectory and other parameters.

Merged service environment
All Windows services can be passed additional environment variables by
creating a multi-valued string (REG_MULTI_SZ) registry value named

The contents of this environment block will be merged into the system
environment before the service starts.

Note, however, that the merged environment will be sorted alphabetically
before being processed. This means that in practice you cannot set,
for example, DIR=%PROGRAMFILES% in the Environment block because the
environment passed to the service will not have defined %PROGRAMFILES%
by the time it comes to define %DIR%. Environment variables defined in
AppEnvironmentExtra do not suffer from this limitation.

As of version 2.25, NSSM can get and set the Environment block using
commands similar to:

nssm get Environment

It is worth reiterating that the Environment block is available to all
Windows services, not just NSSM services.

Service startup environment
The environment NSSM passes to the application depends on how various
registry values are configured. The following flow describes how the
environment is modified.

By default:
The service inherits the system environment.

If \Environment is defined:
The contents of Environment are MERGED into the environment.

If \Parameters\AppEnvironment is defined:
The service inherits the environment specified in AppEnvironment.

If \Parameters\AppEnvironmentExtra is defined:
The contents of AppEnvironmentExtra are APPENDED to the environment.

Note that AppEnvironment overrides the system environment and the
merged Environment block. Note also that AppEnvironmentExtra is
guaranteed to be appended to the startup environment if it is defined.

Event hooks
NSSM can run user-configurable commands in response to application events.
These commands are referred to as "hooks" below.

All hooks are optional. Any hooks which are run will be launched with the
environment configured for the service. NSSM will place additional
variables into the environment which hooks can query to learn how and why
they were called.

Hooks are categorised by Event and Action. Some hooks are run synchronously
and some are run asynchronously. Hooks prefixed with an *asterisk are run
synchronously. NSSM will wait for these hooks to complete before continuing
its work. Note, however, that ALL hooks are subject to a deadline after which
they will be killed, regardless of whether they are run asynchronously
or not.

Event: Start - Triggered when the service is requested to start.
*Action: Pre - Called before NSSM attempts to launch the application.
Action: Post - Called after the application successfully starts.

Event: Stop - Triggered when the service is requested to stop.
*Action: Pre - Called before NSSM attempts to kill the application.

Event: Exit - Triggered when the application exits.
*Action: Post - Called after NSSM has cleaned up the application.

Event: Rotate - Triggered when online log rotation is requested.
*Action: Pre - Called before NSSM rotates logs.
Action: Post - Called after NSSM rotates logs.

Event: Power
Action: Change - Called when the system power status has changed.
Action: Resume - Called when the system has resumed from standby.

Note that there is no Stop/Post hook. This is because Exit/Post is called
when the application exits, regardless of whether it did so in response to
a service shutdown request. Stop/Pre is only called before a graceful
shutdown attempt.

NSSM sets the environment variable NSSM_HOOK_VERSION to a positive number.
Hooks can check the value of the number to determine which other environment
variables are available to them.

If NSSM_HOOK_VERSION is 1 or greater, these variables are provided:

NSSM_EXE - Path to NSSM itself.
NSSM_CONFIGURATION - Build information for the NSSM executable,
eg 64-bit debug.
NSSM_VERSION - Version of the NSSM executable.
NSSM_BUILD_DATE - Build date of NSSM.
NSSM_PID - Process ID of the running NSSM executable.
NSSM_DEADLINE - Deadline number of milliseconds after which NSSM will
kill the hook if it is still running.
NSSM_SERVICE_NAME - Name of the service controlled by NSSM.
NSSM_SERVICE_DISPLAYNAME - Display name of the service.
NSSM_COMMAND_LINE - Command line used to launch the application.
NSSM_APPLICATION_PID - Process ID of the primary application process.
May be blank if the process is not running.
NSSM_EVENT - Event class triggering the hook.
NSSM_ACTION - Event action triggering the hook.
NSSM_TRIGGER - Service control triggering the hook. May be blank if
the hook was not triggered by a service control, eg Exit/Post.
NSSM_LAST_CONTROL - Last service control handled by NSSM.
NSSM_START_REQUESTED_COUNT - Number of times the application was
requested to start.
NSSM_START_COUNT - Number of times the application successfully started.
NSSM_THROTTLE_COUNT - Number of times the application ran for less than
the throttle period. Reset to zero on successful start or when the
service is explicitly unpaused.
NSSM_EXIT_COUNT - Number of times the application exited.
NSSM_EXITCODE - Exit code of the application. May be blank if the
application is still running or has not started yet.
NSSM_RUNTIME - Number of milliseconds for which the NSSM executable has
been running.
NSSM_APPLICATION_RUNTIME - Number of milliseconds for which the
application has been running since it was last started. May be blank
if the application has not been started yet.

Future versions of NSSM may provide more environment variables, in which
case NSSM_HOOK_VERSION will be set to a higher number.

Hooks are configured by creating string (REG_EXPAND_SZ) values in the
registry named after the hook action and placed under

For example the service could be configured to restart when the system
resumes from standby by setting AppEvents\Power\Resume to:


To set a hook on the command line, use

nssm set AppEvents /

Note that NSSM will abort the startup of the application if a Start/Pre hook
returns exit code of 99.

A service will normally run hooks in the following order:


If the application crashes and is restarted by NSSM, the order might be:


If NSSM is redirecting stdout or stderr it can be configured to redirect
the output of any hooks it runs. Set AppRedirectHooks to 1 to enable
that functionality. A hook can of course redirect its own I/O independently
of NSSM.

Managing services using the GUI
NSSM can edit the settings of existing services with the same GUI that is
used to install them. Run

nssm edit

to bring up the GUI.

NSSM offers limited editing capabilities for services other than those which
run NSSM itself. When NSSM is asked to edit a service which does not have
the App* registry settings described above, the GUI will allow editing only
system settings such as the service display name and description.

Managing services using the command line
NSSM can retrieve or set individual service parameters from the command line.
In general the syntax is as follows, though see below for exceptions.

nssm get

nssm set

Parameters can also be reset to their default values.

nssm reset

The parameter names recognised by NSSM are the same as the registry entry
names described above, eg AppDirectory.

NSSM offers limited editing capabilities for Services other than those which
run NSSM itself. The parameters recognised are as follows:

Description: Service description.
DisplayName: Service display name.
Environment: Service merged environment.
ImagePath: Path to the service executable.
ObjectName: User account which runs the service.
Name: Service key name.
Start: Service startup type.
Type: Service type.

These correspond to the registry values under the service's key

Note that NSSM will concatenate all arguments passed on the command line
with spaces to form the value to set. Thus the following two invocations
would have the same effect.

nssm set Description "NSSM managed service"

nssm set Description NSSM managed service

Non-standard parameters
The AppEnvironment, AppEnvironmentExtra and Environment parameters
recognise an additional argument when querying the environment. The
following syntax will print all extra environment variables configured
for a service

nssm get AppEnvironmentExtra

whereas the syntax below will print only the value of the CLASSPATH
variable if it is configured in the environment block, or the empty string
if it is not configured.

nssm get AppEnvironmentExtra CLASSPATH

When setting an environment block, each variable should be specified as a
KEY=VALUE pair in separate command line arguments. For example:

nssm set AppEnvironment CLASSPATH=C:\Classes TEMP=C:\Temp

Alternatively the KEY can be prefixed with a + or - symbol to respectively
add or remove a pair from the block.

The following two lines set CLASSPATH and TEMP:

nssm set AppEnvironment CLASSPATH=C:\Classes
nssm set AppEnvironment +TEMP=C:\Temp

If the key is already present, specifying +KEY will override the value
while preserving the order of keys:

nssm set AppEnvironment +CLASSPATH=C:\NewClasses

The following syntax removes a single variable from the block while
leaving any other variables in place.

nssm set AppEnvironment -TEMP

Specifying -KEY=VALUE will remove the variable only if the existing
value matches.

The following syntax would not remove TEMP=C:\Temp

nssm set AppEnvironment -TEMP=C:\Work\Temporary

The + and - symbols are valid characters in environment variables.
The syntax :KEY=VALUE is equivalent to KEY=VALUE and can be used to
set variables which start with +/- or to explicitly reset the block in
a script:

nssm set AppEnvironment :CLASSPATH=C:\Classes
nssm set AppEnvironment +TEMP=C:\Temp

The AppExit parameter requires an additional argument specifying the exit
code to get or set. The default action can be specified with the string

For example, to get the default exit action for a service you should run

nssm get AppExit Default

To get the exit action when the application exits with exit code 2, run

nssm get AppExit 2

Note that if no explicit action is configured for a specified exit code,
NSSM will print the default exit action.

To set configure the service to stop when the application exits with an
exit code of 2, run

nssm set AppExit 2 Exit

The AppPriority parameter is used to set the priority class of the
managed application. Valid priorities are as follows:


The DependOnGroup and DependOnService parameters are used to query or set
the dependencies for the service. When setting dependencies, each service
or service group (preceded with the + symbol) should be specified in
separate command line arguments. For example:

nssm set DependOnService RpcSs LanmanWorkstation

Alternatively the dependency name can be prefixed with a + or - symbol to
respectively add or remove a dependency.

The following two lines set dependencies on RpcSs and LanmanWorkstation:

nssm set DependOnService RpcSs
nssm set DependOnService +LanmanWorkstation

The follwing syntax removes the dependency on RpcSs:

nssm set DependOnService -RpcSs

Service groups should, strictly speaking, be prefixed with the + symbol.
To specify a single dependency on a group, the + symbol can be prefixed
with the : symbol.

The following lines are equivalent, and each set a dependency ONLY on

nssm set DependOnGroup NetBIOSGroup
nssm set DependOnGroup :NetBIOSGroup
nssm set DependOnGroup :+NetBIOSGroup

Whereas these lines add to any existing dependencies:

nssm set DependOnGroup +NetBIOSGroup
nssm set DependOnGroup ++NetBIOSGroup

The Name parameter can only be queried, not set. It returns the service's
registry key name. This may be useful to know if you take advantage of
the fact that you can substitute the service's display name anywhere where
the syntax calls for .

The ObjectName parameter requires an additional argument only when setting
a username. The additional argument is the password of the user.

To retrieve the username, run

nssm get ObjectName

To set the username and password, run

nssm set ObjectName

Note that the rules of argument concatenation still apply. The following
invocation is valid and will have the expected effect.

nssm set ObjectName correct horse battery staple

The following well-known usernames do not need a password. The password
parameter can be omitted when using them:

"LocalSystem" aka "System" aka "NT Authority\System"
"LocalService" aka "Local Service" aka "NT Authority\Local Service"
"NetworkService" aka "Network Service" aka "NT Authority\Network Service"
Virtual service account "NT Service\"

The Start parameter is used to query or set the startup type of the service.
Valid service startup types are as follows:

SERVICE_AUTO_START: Automatic startup at boot.
SERVICE_DELAYED_START: Delayed startup at boot.
SERVICE_DEMAND_START: Manual service startup.
SERVICE_DISABLED: The service is disabled.

Note that SERVICE_DELAYED_START is not supported on versions of Windows prior
to Vista. NSSM will set the service to automatic startup if delayed start is

The Type parameter is used to query or set the service type. NSSM recognises
all currently documented service types but will only allow setting one of two

SERVICE_WIN32_OWN_PROCESS: A standalone service. This is the default.
SERVICE_INTERACTIVE_PROCESS: A service which can interact with the desktop.

Note that a service may only be configured as interactive if it runs under
the LocalSystem account. The safe way to configure an interactive service
is in two stages as follows.

nssm reset ObjectName

Controlling services using the command line
NSSM offers rudimentary service control features.

nssm start

nssm restart

nssm stop

nssm status

nssm statuscode

The output of "nssm status" and "nssm statuscode" is a string
representing the service state, eg SERVICE_RUNNING.

The exit code of "nssm status" will be 0 if the status was
succesfully retrieved. If the exit code is not zero there was
an error.

The exit code of "nssm statuscode" will be the numeric value
of the service state, eg 4 for SERVICE_RUNNING. Zero is not a
valid service state code. If the exit code is zero there was
an error.

Removing services using the GUI
NSSM can also remove services. Run

nssm remove

to remove a service. You will prompted for confirmation before the service
is removed. Try not to remove essential system services...

Removing service using the command line
To remove a service without confirmation from the GUI, run

nssm remove confirm

Try not to remove essential system services...

NSSM logs to the Windows event log. It registers itself as an event log source
and uses unique event IDs for each type of message it logs. New versions may
add event types but existing event IDs will never be changed.

Because of the way NSSM registers itself you should be aware that you may not
be able to replace the NSSM binary if you have the event viewer open and that
running multiple instances of NSSM from different locations may be confusing if
they are not all the same version.

Listing managed services
The following command will print the names of all services managed by NSSM:

nssm list

To see all services on the system, not just NSSM's, use list all:

nssm list all

Showing processes started by a service
The following command will print the process ID and executable path of
processes started by a given service:

nssm processes

Note that if 32-bit NSSM is run on a 64-bit system running an older version of
Windows than Vista it will not be able to query the paths of 64-bit processes.

Exporting service configuration
NSSM can dump commands which would recreate the configuration of a service.
The output can be pasted into a batch script to back up the service or
transfer to another computer.

nssm dump

Because the service configuration may contain characters which need to be
quoted or escaped from the command prompt, NSSM tries hard to produce
output which will work correctly when run as a script, by adding quotes
and caret escapes as appropriate.

To facilitate copying a service, the dump command accepts a second
argument which specifies the name of the service to be used in the output.

nssm dump

Lines in the dump will reference the service while showing the
configuration of .

Example usage
To install an Unreal Tournament server:

nssm install UT2004 c:\games\ut2004\system\ucc.exe server

To run the server as the "games" user:

nssm set UT2004 ObjectName games password

To configure the server to log to a file:

nssm set UT2004 AppStdout c:\games\ut2004\service.log

To restrict the server to a single CPU:

nssm set UT2004 AppAffinity 0

To remove the server:

nssm remove UT2004 confirm

To find out the service name of a service with a display name:

nssm get "Background Intelligent Transfer Service" Name

Building NSSM from source
NSSM is known to compile with Visual Studio 2008 and later. Older Visual
Studio releases may or may not work if you install an appropriate SDK and
edit the nssm.vcproj and nssm.sln files to set a lower version number.
They are known not to work with default settings.

NSSM will also compile with Visual Studio 2010 but the resulting executable
will not run on versions of Windows older than XP SP2. If you require
compatiblity with older Windows releases you should change the Platform
Toolset to v90 in the General section of the project's Configuration

Thanks to Bernard Loh for finding a bug with service recovery.
Thanks to Benjamin Mayrargue ( for adding 64-bit support.
Thanks to Joel Reingold for spotting a command line truncation bug.
Thanks to Arve Knudsen for spotting that child processes of the monitored
application could be left running on service shutdown, and that a missing
registry value for AppDirectory confused NSSM.
Thanks to Peter Wagemans and Laszlo Keresztfalvi for suggesting throttling
Thanks to Eugene Lifshitz for finding an edge case in CreateProcess() and for
advising how to build correctly in paths containing spaces.
Thanks to Rob Sharp for pointing out that NSSM did not respect the
AppEnvironment registry value used by srvany.
Thanks to Szymon Nowak for help with Windows 2000 compatibility.
Thanks to François-Régis Tardy and Gildas le Nadan for French translation.
Thanks to Emilio Frini for spotting that French was inadvertently set as
the default language when the user's display language was not translated.
Thanks to Riccardo Gusmeroli and Marco Certelli for Italian translation.
Thanks to Eric Cheldelin for the inspiration to generate a Control-C event
on shutdown.
Thanks to Brian Baxter for suggesting how to escape quotes from the command
Thanks to Russ Holmann for suggesting that the shutdown timeout be configurable.
Thanks to Paul Spause for spotting a bug with default registry entries.
Thanks to BUGHUNTER for spotting more GUI bugs.
Thanks to Doug Watson for suggesting file rotation.
Thanks to Арслан Сайдуганов for suggesting setting process priority.
Thanks to Robert Middleton for suggestion and draft implementation of process
affinity support.
Thanks to Andrew RedzMax for suggesting an unconditional restart delay.
Thanks to Bryan Senseman for noticing that applications with redirected stdout
and/or stderr which attempt to read from stdin would fail.
Thanks to Czenda Czendov for help with Visual Studio 2013 and Server 2012R2.
Thanks to Alessandro Gherardi for reporting and draft fix of the bug whereby
the second restart of the application would have a corrupted environment.
Thanks to Hadrien Kohl for suggesting to disable the console window's menu.
Thanks to Allen Vailliencourt for noticing bugs with configuring the service to
run under a local user account.
Thanks to Sam Townsend for noticing a regression with TerminateProcess().
Thanks to Barrett Lewis for suggesting the option to skip terminating the
application's child processes.
Thanks to Miguel Angel Terrón for suggesting copy/truncate rotation.
Thanks to Yuriy Lesiuk for suggesting setting the environment before querying
the registry for parameters.
Thanks to Gerald Haider for noticing that installing a service with NSSM in a
path containing spaces was technically a security vulnerability.
Thanks to Scott Ware for reporting a crash saving the environment on XP 32-bit.
Thanks to Stefan and Michael Scherer for reporting a bug writing the event messages source.
Thanks to Paul Baxter for help with Visual Studio 2015.
Thanks to Mathias Breiner for help with Visual Studio and some registry fixes.
Thanks to David Bremner for general tidyups.
Thanks to Nabil Redmann for suggesting redirecting hooks' output.
Thanks to Bader Aldurai for suggesting the process tree.
Thanks to Christian Long for suggesting virtual accounts.
Thanks to Marcin Lewandowski for spotting a bug appending to large files.
Thanks to Nicolas Ducrocq for suggesting timestamping redirected output.
Thanks to Meang Akira Tanaka for suggestion and initial implementation of
the statuscode command.
Thanks to Kirill Kovalenko for reporting a crash with NANO server.
Thanks to Connor Reynolds for spotting a potential buffer overflow.
Thanks to foi for spotting a hang with 64 cores.

NSSM is public domain. You may unconditionally use it and/or its source code
for any purpose you wish.