The Non-Sucking Service Manager

Iain Patterson 54438652fa Allocate a new console for stdin. 10 years ago
ChangeLog.txt 7fdd3f6c44 Added mandatory restart delay. 10 years ago
README.txt 54438652fa Allocate a new console for stdin. 10 years ago
env.cpp 2e3a41e1d5 Added more environment functions. 10 years ago
env.h 2e3a41e1d5 Added more environment functions. 10 years ago
event.cpp 3f77c8a2c0 Extra product description tags. 10 years ago
event.h 8754d6de6c Be more Windowsy. 10 years ago
gui.cpp 1d07940617 Fixed warning when file disposition isn't set. 10 years ago
gui.h 2c60e5334f Allow editing services. 10 years ago
imports.cpp 04368b24e4 Fixed arguments to mbstowcs_s(). 10 years ago
imports.h 5b9e64a9ae Allow compiling as a Unicode application. 10 years ago
io.cpp 54438652fa Allocate a new console for stdin. 10 years ago
io.h ba4831e5eb Fixed CreateFile() flags when opening log files. 10 years ago fa2f3fe4a8 Fake stdin for applications which exit on EOF. 10 years ago
nssm.cpp 23bed76e3a Allow restarting a service. 10 years ago
nssm.h e3b93d0c37 Moved environment functions to a new file. 10 years ago
nssm.ico d6ce7c473f New URL and icon. 12 years ago
nssm.rc bef1f20a0b French CPUs are UCs. 10 years ago
nssm.sln 7b62a11307 Tidy up build directories. 10 years ago
nssm.vcproj e3b93d0c37 Moved environment functions to a new file. 10 years ago
process.cpp 54438652fa Allocate a new console for stdin. 10 years ago
process.h e3b93d0c37 Moved environment functions to a new file. 10 years ago
registry.cpp eac4d7eedf Revamped environment variables again. 10 years ago
registry.h 77855b77fa Renamed set_environment(). 10 years ago
resource.h 143238dfe3 Rotate files while the service is running. 10 years ago
service.cpp 54438652fa Allocate a new console for stdin. 10 years ago
service.h 54438652fa Allocate a new console for stdin. 10 years ago
settings.cpp 77855b77fa Renamed set_environment(). 10 years ago
settings.h 121d394369 Allow querying a service's name. 10 years ago
version.cmd b2e2a895d7 Fixed year marker in build information. 10 years ago


NSSM: The Non-Sucking Service Manager
Version 2.21, 2013-11-24

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 and log on details.

Since version 2.22, NSSM can manage existing services.

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.

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.

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.

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.

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.
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 and AppEnvironmentExtra 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

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 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 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

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.

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 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 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.

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