NAME¶

mono - Mono's ECMA-CLI native code generator (Just-in-Time and Ahead-of-Time)

SYNOPSIS¶

mono [options] file [arguments...]

mono-sgen [options] file [arguments...]

DESCRIPTION¶

mono is a runtime implementation of the ECMA Common Language Infrastructure. This can be used to run ECMA and .NET applications.

The runtime loads the specified file and optionally passes the arguments to it. The file is an ECMA assembly. They typically have a .exe or .dll extension.

These executables can reference additional functionality in the form of assembly references. By default those assembly references are resolved as follows: the mscorlib.dll is resolved from the system profile that is configured by Mono, and other assemblies are loaded from the Global Assembly Cache (GAC).

The runtime contains a native code generator that transforms the Common Intermediate Language into native code.

The code generator can operate in two modes: Just-in-time compilation (JIT) or Ahead-of-time compilation (AOT). Since code can be dynamically loaded, the runtime environment and the JIT are always present, even if code is compiled ahead of time.

The runtime provides a number of configuration options for running applications, for developing and debugging, and for testing and debugging the runtime itself.

The mono command uses the moving and generational SGen garbage collector while the mono-boehm command uses the conservative Boehm garbage collector.

PORTABILITY¶

On Unix-based systems, Mono provides a mechanism to emulate the Windows-style file access, this includes providing a case insensitive view of the file system, directory separator mapping (from \ to /) and stripping the drive letters.

This functionality is enabled by setting the MONO_IOMAP environment variable to one of all, drive and case.

See the description for MONO_IOMAP in the environment variables section for more details.

METHOD DESCRIPTIONS¶

A number of diagnostic command line options take as argument a method description. A method description is a textual representation that can be used to uniquely identify a method. The syntax is as follows:

[namespace]classname:methodname[(arguments)]

The values in brackets are optional, like the namespace and the arguments. The arguments themselves are either empty, or a comma-separated list of arguments. Both the classname and methodname can be set to the special value '*' to match any values (Unix shell users should escape the argument to avoid the shell interpreting this).

The arguments, if present should be a comma separated list of types either a full typename, or for built-in types it should use the low-level ILAsm type names for the built-in types, like 'void', 'char', 'bool', 'byte', 'sbyte', 'uint16', 'int16', 'uint',

Pointer types should be the name of the type, followed by a '*', arrays should be the typename followed by '[' one or more commas (to indicate the rank of the array), and ']'.

Generic values should use '<', one or more type names, separated by both a comma and a space and '>'.

By-reference arguments should include a "&" after the typename.

Examples:

*:ctor(int)		// All constructors that take an int as an argument
*:Main			// Methods named Main in any class
*:Main(string[])	// Methods named Main that take a string array in any class

RUNTIME OPTIONS¶

The following options are available:

--aot, --aot[=options]

This option is used to precompile the CIL code in the specified assembly to native code. The generated code is stored in a file with the extension .so. This file will be automatically picked up by the runtime when the assembly is executed. Ahead-of-Time compilation is most useful if you use it in combination with the -O=all,-shared flag which enables all of the optimizations in the code generator to be performed. Some of those optimizations are not practical for Just-in-Time compilation since they might be very time consuming. Unlike the .NET Framework, Ahead-of-Time compilation will not generate domain independent code: it generates the same code that the Just-in-Time compiler would produce. Since most applications use a single domain, this is fine. If you want to optimize the generated code for use in multi-domain applications, consider using the -O=shared flag. This pre-compiles the methods, but the original assembly is still required to execute as this one contains the metadata and exception information which is not available on the generated file. When precompiling code, you might want to compile with all optimizations (-O=all). Pre-compiled code is position independent code. Precompilation is just a mechanism to reduce startup time, increase code sharing across multiple mono processes and avoid just-in-time compilation program startup costs. The original assembly must still be present, as the metadata is contained there. AOT code typically can not be moved from one computer to another (CPU-specific optimizations that are detected at runtime) so you should not try to move the pre-generated assemblies or package the pre-generated assemblies for deployment. A few options are available as a parameter to the --aot command line option. The options are separated by commas, and more than one can be specified:

--aot-path=PATH

List of additional directories to search for AOT images.

--apply-bindings=FILE

Apply the assembly bindings from the specified configuration file when running the AOT compiler. This is useful when compiling an auxiliary assembly that is referenced by a main assembly that provides a configuration file. For example, if app.exe uses lib.dll then in order to make the assembly bindings from app.exe.config available when compiling lib.dll ahead of time, use:

	mono --apply-bindings=app.exe.config --aot lib.dll

--assembly-loader=MODE

If mode is strict, Mono will check that the public key token, culture and version of a candidate assembly matches the requested strong name. If mode is legacy, as long as the name matches, the candidate will be allowed. strict is the behavior consistent with .NET Framework but may break some existing mono-based applications. The default is legacy.

--attach=[options]

Currently the only option supported by this command line argument is disable which disables the attach functionality.

--config filename

Load the specified configuration file instead of the default one(s). The default files are /etc/mono/config and ~/.mono/config or the file specified in the MONO_CONFIG environment variable, if set. See the mono-config(5) man page for details on the format of this file.

--debugger-agent=[options]

This instructs the Mono runtime to start a debugging agent inside the Mono runtime and connect it to a client user interface will control the Mono process. This option is typically used by IDEs, like the MonoDevelop or Visual Studio IDEs.

DEVELOPMENT OPTIONS¶

The following options are used to help when developing a JITed application.

--debug, --debug=OPTIONS

Turns on the debugging mode in the runtime. If an assembly was compiled with debugging information, it will produce line number information for stack traces.

--profile[=profiler[:profiler_args]]

Loads a profiler module with the given arguments. For more information, see the PROFILING section. This option can be used multiple times; each time will load an additional profiler module.

--trace[=expression]

Shows method names as they are invoked. By default all methods are traced. The trace can be customized to include or exclude methods, classes or assemblies. A trace expression is a comma separated list of targets, each target can be prefixed with a minus sign to turn off a particular target. The words `program', `all' and `disabled' have special meaning. `program' refers to the main program being executed, and `all' means all the method calls. The `disabled' option is used to start up with tracing disabled. It can be enabled at a later point in time in the program by sending the SIGUSR2 signal to the runtime. Assemblies are specified by their name, for example, to trace all calls in the System assembly, use:

	mono --trace=System app.exe
    

Classes are specified with the T: prefix. For example, to trace all calls to the System.String class, use:

	mono --trace=T:System.String app.exe
    

And individual methods are referenced with the M: prefix, and the standard method notation:

	mono --trace=M:System.Console:WriteLine app.exe
    

Exceptions can also be traced, it will cause a stack trace to be printed every time an exception of the specified type is thrown. The exception type can be specified with or without the namespace, and to trace all exceptions, specify 'all' as the type name.

	mono --trace=E:System.Exception app.exe
    

As previously noted, various rules can be specified at once:

	mono --trace=T:System.String,T:System.Random app.exe
    

You can exclude pieces, the next example traces calls to System.String except for the System.String:Concat method.

	mono --trace=T:System.String,-M:System.String:Concat
    

You can trace managed to unmanaged transitions using the wrapper qualifier:

	mono --trace=wrapper app.exe
    

Finally, namespaces can be specified using the N: prefix:

	mono --trace=N:System.Xml
    

--no-x86-stack-align

Don't align stack frames on the x86 architecture. By default, Mono aligns stack frames to 16 bytes on x86, so that local floating point and SIMD variables can be properly aligned. This option turns off the alignment, which usually saves one instruction per call, but might result in significantly lower floating point and SIMD performance.

--jitmap

Generate a JIT method map in a /tmp/perf-PID.map file. This file is then used, for example, by the perf tool included in recent Linux kernels. Each line in the file has:

	HEXADDR HEXSIZE methodname
    

Currently this option is only supported on Linux.

JIT MAINTAINER OPTIONS¶

The maintainer options are only used by those developing the runtime itself, and not typically of interest to runtime users or developers.

--bisect=optimization:filename

This flag is used by the automatic optimization bug bisector. It takes an optimization flag and a filename of a file containing a list of full method names, one per line. When it compiles one of the methods in the file it will use the optimization given, in addition to the optimizations that are otherwise enabled. Note that if the optimization is enabled by default, you should disable it with `-O`, otherwise it will just apply to every method, whether it's in the file or not.

--break method

Inserts a breakpoint before the method whose name is `method' (namespace.class:methodname). Use `Main' as method name to insert a breakpoint on the application's main method. You can use it also with generics, for example "System.Collections.Generic.Queue`1:Peek"

--breakonex

Inserts a breakpoint on exceptions. This allows you to debug your application with a native debugger when an exception is thrown.

--compile name

This compiles a method (namespace.name:methodname), this is used for testing the compiler performance or to examine the output of the code generator.

--compile-all

Compiles all the methods in an assembly. This is used to test the compiler performance or to examine the output of the code generator

--graph=TYPE METHOD

This generates a postscript file with a graph with the details about the specified method (namespace.name:methodname). This requires `dot' and ghostview to be installed (it expects Ghostview to be called "gv"). The following graphs are available:

          cfg        Control Flow Graph (CFG)


          dtree      Dominator Tree


          code       CFG showing code


          ssa        CFG showing code after SSA translation


          optcode    CFG showing code after IR optimizations

Some graphs will only be available if certain optimizations are turned on.

--ncompile

Instruct the runtime on the number of times that the method specified by --compile (or all the methods if --compile-all is used) to be compiled. This is used for testing the code generator performance.

--stats=[method]

Displays information about the work done by the runtime during the execution of an application. If a method (namespace.name:methodname) is specified, it will display that information when the method is first run in addition to the end of program execution.

--wapi=hps|semdel

Perform maintenance of the process shared data. semdel will delete the global semaphore. hps will list the currently used handles.

-v, --verbose

Increases the verbosity level, each time it is listed, increases the verbosity level to include more information (including, for example, a disassembly of the native code produced, code selector info etc.).

ATTACH SUPPORT¶

The Mono runtime allows external processes to attach to a running process and load assemblies into the running program. To attach to the process, a special protocol is implemented in the Mono.Management assembly.

With this support it is possible to load assemblies that have an entry point (they are created with -target:exe or -target:winexe) to be loaded and executed in the Mono process.

The code is loaded into the root domain, and it starts execution on the special runtime attach thread. The attached program should create its own threads and return after invocation.

This support allows for example debugging applications by having the csharp shell attach to running processes.

PROFILING¶

The Mono runtime includes a profiler API that dynamically loaded profiler modules and embedders can use to collect performance-related data about an application. Profiler modules are loaded by passing the --profile command line argument to the Mono runtime.

Mono ships with a few profiler modules, of which the log profiler is the most feature-rich. It is also the default profiler if the profiler argument is not given, or if default is given. It is possible to write your own profiler modules; see the Custom profilers sub-section.

mono --profile=custom program.exe

mono --profile=custom:arg1,arg2=arg3 program.exe

DEBUGGING AIDS¶

To debug managed applications, you can use the mdb command, a command line debugger.

It is possible to obtain a stack trace of all the active threads in Mono by sending the QUIT signal to Mono, you can do this from the command line, like this:

	kill -QUIT pid

Important: this is a last-resort mechanism for debugging applications and should not be used to monitor or probe a production application. The integrity of the runtime after sending this signal is not guaranteed and the application might crash or terminate at any given point afterwards.

The --debug=casts option can be used to get more detailed information for Invalid Cast operations, it will provide information about the types involved.

You can use the MONO_LOG_LEVEL and MONO_LOG_MASK environment variables to get verbose debugging output about the execution of your application within Mono.

The MONO_LOG_LEVEL environment variable if set, the logging level is changed to the set value. Possible values are "error", "critical", "warning", "message", "info", "debug". The default value is "error". Messages with a logging level greater then or equal to the log level will be printed to stdout/stderr.

Use "info" to track the dynamic loading of assemblies.

Use the MONO_LOG_MASK environment variable to limit the extent of the messages you get: If set, the log mask is changed to the set value. Possible values are "asm" (assembly loader), "type", "dll" (native library loader), "gc" (garbage collector), "cfg" (config file loader), "aot" (precompiler), "security" (e.g. Moonlight CoreCLR support), "threadpool" (thread pool generic), "io-selector" (async socket operations), "io-layer" (I/O layer - processes, files, sockets, events, semaphores, mutexes and handles), "io-layer-process", "io-layer-file", "io-layer-socket", "io-layer-event", "io-layer-semaphore", "io-layer-mutex", "io-layer-handle" and "all". The default value is "all". Changing the mask value allows you to display only messages for a certain component. You can use multiple masks by comma separating them. For example to see config file messages and assembly loader messages set you mask to "asm,cfg".

The following is a common use to track down problems with P/Invoke:

	$ MONO_LOG_LEVEL="debug" MONO_LOG_MASK="dll" mono glue.exe

DEBUGGING WITH LLDB¶

If you are using LLDB, you can use the mono.py script to print some internal data structures with it. To use this, add this to your $HOME/.lldbinit file:

command script import $PREFIX/lib/mono/lldb/mono.py

Where $PREFIX is the prefix value that you used when you configured Mono (typically /usr).

Once this is done, then you can inspect some Mono Runtime data structures, for example:

(lldb) p method
(MonoMethod *) $0 = 0x05026ac0 [mscorlib]System.OutOfMemoryException:.ctor()

SERIALIZATION¶

Mono's XML serialization engine by default will use a reflection-based approach to serialize which might be slow for continuous processing (web service applications). The serialization engine will determine when a class must use a hand-tuned serializer based on a few parameters and if needed it will produce a customized C# serializer for your types at runtime. This customized serializer then gets dynamically loaded into your application.

You can control this with the MONO_XMLSERIALIZER_THS environment variable.

The possible values are `no' to disable the use of a C# customized serializer, or an integer that is the minimum number of uses before the runtime will produce a custom serializer (0 will produce a custom serializer on the first access, 50 will produce a serializer on the 50th use). Mono will fallback to an interpreted serializer if the serializer generation somehow fails. This behavior can be disabled by setting the option `nofallback' (for example: MONO_XMLSERIALIZER_THS=0,nofallback).

ENVIRONMENT VARIABLES¶

GC_DONT_GC

Turns off the garbage collection in Mono. This should be only used for debugging purposes

HTTP_PROXY

(Also http_proxy) If set, web requests using the Mono Class Library will be automatically proxied through the given URL. Not supported on Windows, Mac OS, iOS or Android. See also NO_PROXY.

LLVM_COUNT

When Mono is compiled with LLVM support, this instructs the runtime to stop using LLVM after the specified number of methods are JITed. This is a tool used in diagnostics to help isolate problems in the code generation backend. For example LLVM_COUNT=10 would only compile 10 methods with LLVM and then switch to the Mono JIT engine. LLVM_COUNT=0 would disable the LLVM engine altogether.

MONO_ASPNET_INHIBIT_SETTINGSMAP

Mono contains a feature which allows modifying settings in the .config files shipped with Mono by using config section mappers. The mappers and the mapping rules are defined in the $prefix/etc/mono/2.0/settings.map file and, optionally, in the settings.map file found in the top-level directory of your ASP.NET application. Both files are read by System.Web on application startup, if they are found at the above locations. If you don't want the mapping to be performed you can set this variable in your environment before starting the application and no action will be taken.

MONO_ASPNET_WEBCONFIG_CACHESIZE

Mono has a cache of ConfigSection objects for speeding up WebConfigurationManager queries. Its default size is 100 items, and when more items are needed, cache evictions start happening. If evictions are too frequent this could impose unnecessary overhead, which could be avoided by using this environment variable to set up a higher cache size (or to lower memory requirements by decreasing it).

MONO_CAIRO_DEBUG_DISPOSE

If set, causes Mono.Cairo to collect stack traces when objects are allocated, so that the finalization/Dispose warnings include information about the instance's origin.

MONO_CFG_DIR

If set, this variable overrides the default system configuration directory ($PREFIX/etc). It's used to locate machine.config file.

MONO_COM

Sets the style of COM interop. If the value of this variable is "MS" Mono will use string marhsalling routines from the liboleaut32 for the BSTR type library, any other values will use the mono-builtin BSTR string marshalling.

MONO_CONFIG

If set, this variable overrides the default runtime configuration file ($PREFIX/etc/mono/config). The --config command line options overrides the environment variable.

MONO_CPU_ARCH

Override the automatic cpu detection mechanism. Currently used only on arm. The format of the value is as follows:

	"armvV [thumb[2]]"
    

where V is the architecture number 4, 5, 6, 7 and the options can be currently be "thumb" or "thumb2". Example:

	MONO_CPU_ARCH="armv4 thumb" mono ...
    

MONO_ARM_FORCE_SOFT_FLOAT

When Mono is built with a soft float fallback on ARM and this variable is set to "1", Mono will always emit soft float code, even if a VFP unit is detected.

MONO_DARWIN_USE_KQUEUE_FSW

Fall back on the kqueue FileSystemWatcher implementation in Darwin. The default is the FSEvent implementation.

MONO_DARWIN_WATCHER_MAXFDS

This is a debugging aid used to force limits on the kqueue FileSystemWatcher implementation in Darwin. There is no limit by default.

MONO_DISABLE_MANAGED_COLLATION

If this environment variable is `yes', the runtime uses unmanaged collation (which actually means no culture-sensitive collation). It internally disables managed collation functionality invoked via the members of System.Globalization.CompareInfo class. Collation is enabled by default.

MONO_DISABLE_SHARED_AREA

Unix only: If set, disable usage of shared memory for exposing performance counters. This means it will not be possible to both externally read performance counters from this processes or read those of external processes.

MONO_DNS

When set, enables the use of a fully managed DNS resolver instead of the regular libc functions. This resolver performs much better when multiple queries are run in parallel.

Note that /etc/nsswitch.conf will be ignored.

MONO_EGD_SOCKET

For platforms that do not otherwise have a way of obtaining random bytes this can be set to the name of a file system socket on which an egd or prngd daemon is listening.

MONO_ENABLE_AIO

If set, tells mono to attempt using native asynchronous I/O services. If not set, a default select/poll implementation is used. Currently epoll and kqueue are supported.

MONO_THREADS_SUSPEND Selects a mechanism that Mono will use to suspend

threads. May be set to "preemptive", "coop", or "hybrid". Threads may need to be suspended by the debugger, or using some .NET threading APIs, and most commonly when the SGen garbage collector needs to stop all threads during a critical phase of garbage collection. Preemptive mode is the mode that Mono has used historically, going back to the Boehm days, where the garbage collector would run at any point and suspend execution of all threads as required to perform a garbage collection. The cooperative mode on the other hand requires the cooperation of all threads to stop at a safe point. This makes for an easier to debug garbage collector and it improves the stability of the runtime because threads are not suspended when accessing critical resources. In scenarios where Mono is embedded in another application, cooperative suspend requires the embedder code to follow coding guidelines in order to cooperate with the garbage collector. Cooperative suspend in embedded Mono is currently experimental. Hybrid mode is a combination of the two that retains better compatability with scenarios where Mono is embedded in another application: threads that are running managed code or code that comprises the Mono runtime will be cooperatively suspended, while threads running embedder code will be preemptively suspended. Hybrid suspend is the default on some desktop platforms.

Alternatively, coop and hybrid mode can be enabled at compile time by using the --enable-cooperative-suspend or --enable-hybrid-suspend flags, respectively, when calling configure. The MONO_THREADS_SUSPEND environment variable takes priority over the compiled default.

MONO_ENABLE_COOP_SUSPEND

This environment variable is obsolete, but retained for backward compatibility. Use MONO_THREADS_SUSPEND set to "coop" instead. Note that if configure flags were provided to enable cooperative or hybrid suspend, this variable is ignored.

MONO_ENV_OPTIONS

This environment variable allows you to pass command line arguments to a Mono process through the environment. This is useful for example to force all of your Mono processes to use LLVM or SGEN without having to modify any launch scripts.

MONO_SDB_ENV_OPTIONS

Used to pass extra options to the debugger agent in the runtime, as they were passed using --debugger-agent=.

MONO_EVENTLOG_TYPE

Sets the type of event log provider to use (for System.Diagnostics.EventLog). Possible values are:

MONO_EXTERNAL_ENCODINGS

If set, contains a colon-separated list of text encodings to try when turning externally-generated text (e.g. command-line arguments or filenames) into Unicode. The encoding names come from the list provided by iconv, and the special case "default_locale" which refers to the current locale's default encoding.

When reading externally-generated text strings UTF-8 is tried first, and then this list is tried in order with the first successful conversion ending the search. When writing external text (e.g. new filenames or arguments to new processes) the first item in this list is used, or UTF-8 if the environment variable is not set.

The problem with using MONO_EXTERNAL_ENCODINGS to process your files is that it results in a problem: although its possible to get the right file name it is not necessarily possible to open the file. In general if you have problems with encodings in your filenames you should use the "convmv" program.

MONO_GC_PARAMS

When using Mono with the SGen garbage collector this variable controls several parameters of the collector. The variable's value is a comma separated list of words.

MONO_GC_DEBUG

When using Mono with the SGen garbage collector this environment variable can be used to turn on various debugging features of the collector. The value of this variable is a comma separated list of words. Do not use these options in production.

MONO_GAC_PREFIX

Provides a prefix the runtime uses to look for Global Assembly Caches. Directories are separated by the platform path separator (colons on unix). MONO_GAC_PREFIX should point to the top directory of a prefixed install. Or to the directory provided in the gacutil /gacdir command. Example: /home/username/.mono:/usr/local/mono/

MONO_IOMAP

(deprecated) Enabled some filename rewriting support to assist badly-written applications that hard-code Windows paths. It no longer works as of Mono 6.0.

MONO_LLVM

When Mono is using the LLVM code generation backend you can use this environment variable to pass code generation options to the LLVM compiler.

MONO_MANAGED_WATCHER

If set to "disabled", System.IO.FileSystemWatcher will use a file watcher implementation which silently ignores all the watching requests. If set to any other value, System.IO.FileSystemWatcher will use the default managed implementation (slow). If unset, mono will try to use inotify, FAM, Gamin, kevent under Unix systems and native API calls on Windows, falling back to the managed implementation on error.

MONO_MESSAGING_PROVIDER

Mono supports a plugin model for its implementation of System.Messaging making it possible to support a variety of messaging implementations (e.g. AMQP, ActiveMQ). To specify which messaging implementation is to be used the evironement variable needs to be set to the full class name for the provider. E.g. to use the RabbitMQ based AMQP implementation the variable should be set to:

Mono.Messaging.RabbitMQ.RabbitMQMessagingProvider,Mono.Messaging.RabbitMQ

MONO_NO_SMP

If set causes the mono process to be bound to a single processor. This may be
useful when debugging or working around race conditions.

MONO_NO_TLS

Disable inlining of thread local accesses. Try setting this if you get a segfault
early on in the execution of mono.

MONO_PATH

Provides a search path to the runtime where to look for library
files.   This is a tool convenient for debugging applications, but
should not be used by deployed applications as it breaks the assembly
loader in subtle ways. 
Directories are separated by the platform path separator (colons on unix). Example:
/home/username/lib:/usr/local/mono/lib
Relative paths are resolved based on the launch-time current directory.
Alternative solutions to MONO_PATH include: installing libraries into
the Global Assembly Cache (see gacutil(1)) or having the dependent
libraries side-by-side with the main executable.
For a complete description of recommended practices for application
deployment, see
http://www.mono-project.com/docs/getting-started/application-deployment/

MONO_SHARED_DIR

If set its the directory where the ".wapi" handle state is stored.
This is the directory where the Windows I/O Emulation layer stores its
shared state data (files, events, mutexes, pipes).  By default Mono
will store the ".wapi" directory in the users's home directory.

MONO_SHARED_HOSTNAME

Uses the string value of this variable as a replacement for the host name when
creating file names in the ".wapi" directory. This helps if the host name of
your machine is likely to be changed when a mono application is running or if
you have a .wapi directory shared among several different computers.
Mono typically uses the hostname to create the files that are used to
share state across multiple Mono processes.  This is done to support
home directories that might be shared over the network.

MONO_STRICT_IO_EMULATION

If set, extra checks are made during IO operations.  Currently, this
includes only advisory locks around file writes.

MONO_TLS_PROVIDER

This environment variable controls which TLS/SSL provider Mono will
use.  The options are usually determined by the operating system where
Mono was compiled and the configuration options that were used for
it.   

MONO_TLS_SESSION_CACHE_TIMEOUT

The time, in seconds, that the SSL/TLS session cache will keep it's entry to
avoid a new negotiation between the client and a server. Negotiation are very
CPU intensive so an application-specific custom value may prove useful for 
small embedded systems.
The default is 180 seconds.

MONO_THREADS_PER_CPU

The minimum number of threads in the general threadpool will be 
MONO_THREADS_PER_CPU * number of CPUs. The default value for this
variable is 1.

MONO_XMLSERIALIZER_THS

Controls the threshold for the XmlSerializer to produce a custom
serializer for a given class instead of using the Reflection-based
interpreter.  The possible values are `no' to disable the use of a
custom serializer or a number to indicate when the XmlSerializer
should start serializing.   The default value is 50, which means that
the a custom serializer will be produced on the 50th use.

MONO_X509_REVOCATION_MODE

Sets the revocation mode used when validating a X509 certificate chain (https,
ftps, smtps...).  The default is 'nocheck', which performs no revocation check
at all. The other possible values are 'offline', which performs CRL check (not
implemented yet) and 'online' which uses OCSP and CRL to verify the revocation
status (not implemented yet).

NO_PROXY

(Also no_proxy) If both HTTP_PROXY and NO_PROXY are
set, NO_PROXY will be treated as a comma-separated list of "bypass" domains
which will not be sent through the proxy. Domains in NO_PROXY may contain
wildcards, as in "*.mono-project.com" or "build????.local". Not supported on
Windows, Mac OS, iOS or Android.

ENVIRONMENT VARIABLES FOR DEBUGGING¶

MONO_ASPNET_NODELETE

If set to any value, temporary source files generated by ASP.NET support classes will not be removed. They will be kept in the user's temporary directory.

MONO_DEBUG

If set, enables some features of the runtime useful for debugging. This variable should contain a comma separated list of debugging options. Currently, the following options are supported:

MONO_LOG_LEVEL

The logging level, possible values are `error', `critical', `warning', `message', `info' and `debug'. See the DEBUGGING section for more details.

MONO_LOG_MASK

Controls the domain of the Mono runtime that logging will apply to. If set, the log mask is changed to the set value. Possible values are "asm" (assembly loader), "type", "dll" (native library loader), "gc" (garbage collector), "cfg" (config file loader), "aot" (precompiler), "security" (e.g. Moonlight CoreCLR support) and "all". The default value is "all". Changing the mask value allows you to display only messages for a certain component. You can use multiple masks by comma separating them. For example to see config file messages and assembly loader messages set you mask to "asm,cfg".

MONO_LOG_DEST

Controls where trace log messages are written. If not set then the messages go to stdout. If set, the string either specifies a path to a file that will have messages appended to it, or the string "syslog" in which case the messages will be written to the system log. Under Windows, this is simulated by writing to a file called "mono.log". MONO_LOG_HEADER Controls whether trace log messages not directed to syslog have the id, timestamp, and pid as the prefix to the log message. To enable a header this environment variable need just be non-null.

MONO_TRACE

Used for runtime tracing of method calls. The format of the comma separated trace options is:

	[-]M:method name
	[-]N:namespace
	[-]T:class name
	[-]all
	[-]program
	disabled		Trace output off upon start.
    

You can toggle trace output on/off sending a SIGUSR2 signal to the program.

MONO_TRACE_LISTENER

If set, enables the System.Diagnostics.DefaultTraceListener, which will print the output of the System.Diagnostics Trace and Debug classes. It can be set to a filename, and to Console.Out or Console.Error to display output to standard output or standard error, respectively. If it's set to Console.Out or Console.Error you can append an optional prefix that will be used when writing messages like this: Console.Error:MyProgramName. See the System.Diagnostics.DefaultTraceListener documentation for more information.

MONO_WCF_TRACE

This eases WCF diagnostics functionality by simply outputs all log messages from WCF engine to "stdout", "stderr" or any file passed to this environment variable. The log format is the same as usual diagnostic output.

MONO_XEXCEPTIONS

This throws an exception when a X11 error is encountered; by default a message is displayed but execution continues

MONO_XMLSERIALIZER_DEBUG

Set this value to 1 to prevent the serializer from removing the temporary files that are created for fast serialization; This might be useful when debugging.

MONO_XSYNC

This is used in the System.Windows.Forms implementation when running with the X11 backend. This is used to debug problems in Windows.Forms as it forces all of the commands send to X11 server to be done synchronously. The default mode of operation is asynchronous which makes it hard to isolate the root of certain problems.

MONO_XDEBUG

When the the MONO_XDEBUG env var is set, debugging info for JITted code is emitted into a shared library, loadable into gdb. This enables, for example, to see managed frame names on gdb backtraces.

MONO_VERBOSE_METHOD

Enables the maximum JIT verbosity for the specified method. This is very helpfull to diagnose a miscompilation problems of a specific method. This can be a semicolon-separated list of method names to match. If the name is simple, this applies to any method with that name, otherwise you can use a mono method description (see the section METHOD DESCRIPTIONS).

MONO_JIT_DUMP_METHOD

Enables sending of the JITs intermediate representation for a specified method to the IdealGraphVisualizer tool.

MONO_VERBOSE_HWCAP

If set, makes the JIT output information about detected CPU features (such as SSE, CMOV, FCMOV, etc) to stdout.

MONO_CONSERVATIVE_HWCAP

If set, the JIT will not perform any hardware capability detection. This may be useful to pinpoint the cause of JIT issues. This is the default when Mono is built as an AOT cross compiler, so that the generated code will run on most hardware.

VALGRIND¶

If you want to use Valgrind, you will find the file `mono.supp' useful, it contains the suppressions for the GC which trigger incorrect warnings. Use it like this:

    valgrind --suppressions=mono.supp mono ...

DTRACE¶

On some platforms, Mono can expose a set of DTrace probes (also known as user-land statically defined, USDT Probes).

They are defined in the file `mono.d'.

ves-init-begin, ves-init-end

Begin and end of runtime initialization.

method-compile-begin, method-compile-end

Begin and end of method compilation. The probe arguments are class name, method name and signature, and in case of method-compile-end success or failure of compilation.

gc-begin, gc-end

Begin and end of Garbage Collection.

To verify the availability of the probes, run:

    dtrace -P mono'$target' -l -c mono

PERMISSIONS¶

Mono's Ping implementation for detecting network reachability can create the ICMP packets itself without requiring the system ping command to do the work. If you want to enable this on Linux for non-root users, you need to give the Mono binary special permissions.

As root, run this command:

   # setcap cap_net_raw=+ep /usr/bin/mono

FILES¶

On Unix assemblies are loaded from the installation lib directory. If you set `prefix' to /usr, the assemblies will be located in /usr/lib. On Windows, the assemblies are loaded from the directory where mono and mint live.

~/.mono/aot-cache

The directory for the ahead-of-time compiler demand creation assemblies are located.

/etc/mono/config, ~/.mono/config

Mono runtime configuration file. See the mono-config(5) manual page for more information.

~/.config/.mono/certs, /usr/share/.mono/certs

Contains Mono certificate stores for users / machine. See the certmgr(1) manual page for more information on managing certificate stores and the mozroots(1) page for information on how to import the Mozilla root certificates into the Mono certificate store.

~/.mono/assemblies/ASSEMBLY/ASSEMBLY.config

Files in this directory allow a user to customize the configuration for a given system assembly, the format is the one described in the mono-config(5) page.

~/.config/.mono/keypairs, /usr/share/.mono/keypairs

Contains Mono cryptographic keypairs for users / machine. They can be accessed by using a CspParameters object with DSACryptoServiceProvider and RSACryptoServiceProvider classes.

~/.config/.isolatedstorage, ~/.local/share/.isolatedstorage, /usr/share/.isolatedstorage

Contains Mono isolated storage for non-roaming users, roaming users and local machine. Isolated storage can be accessed using the classes from the System.IO.IsolatedStorage namespace.

<assembly>.config

Configuration information for individual assemblies is loaded by the runtime from side-by-side files with the .config files, see the http://www.mono-project.com/Config for more information.

Web.config, web.config

ASP.NET applications are configured through these files, the configuration is done on a per-directory basis. For more information on this subject see the http://www.mono-project.com/Config_system.web page.

MAILING LISTS¶

Mailing lists are listed at the http://www.mono-project.com/community/help/mailing-lists/

WEB SITE¶

http://www.mono-project.com

SEE ALSO¶

certmgr(1), cert-sync(1), csharp(1), gacutil(1), mcs(1), monodis(1), mono-config(5), mono-profilers(1), mprof-report(1), pdb2mdb(1), xsp(1), mod_mono(8)

For more information on AOT: http://www.mono-project.com/docs/advanced/aot/

For ASP.NET-related documentation, see the xsp(1) manual page