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Dump collection and analysis utility (dotnet-dump)

  • Article

This article applies to: ✔️ dotnet-dump version 3.0.47001 and later versions

Note

dotnet-dump for macOS is only supported with .NET 5 and later versions.

Install

There are two ways to download and install dotnet-dump:

Note

To use dotnet-dump on an x86 app, you need a corresponding x86 version of the tool.

Synopsis

dotnet-dump [-h|--help] [--version] <command>

Description

The dotnet-dump global tool is a way to collect and analyze dumps on Windows, Linux, and macOS without any native debugger involved. This tool is important on platforms like Alpine Linux where a fully working lldb isn't available. The dotnet-dump tool allows you to run SOS commands to analyze crashes and the garbage collector (GC), but it isn't a native debugger so things like displaying native stack frames aren't supported.

Options

  • --version

    Displays the version of the dotnet-dump utility.

  • -h|--help

    Shows command-line help.

Commands

Command
dotnet-dump collect
dotnet-dump analyze
dotnet-dump ps

dotnet-dump collect

Captures a dump from a process.

Synopsis

dotnet-dump collect [-h|--help] [-p|--process-id] [-n|--name] [--type] [-o|--output] [--diag] [--crashreport]

Options

  • -h|--help

    Shows command-line help.

  • -p|--process-id <PID>

    Specifies the process ID number to collect a dump from.

  • -n|--name <name>

    Specifies the name of the process to collect a dump from.

  • --type <Full|Heap|Mini>

    Specifies the dump type, which determines the kinds of information that are collected from the process. There are three types:

    • Full - The largest dump containing all memory including the module images.
    • Heap - A large and relatively comprehensive dump containing module lists, thread lists, all stacks, exception information, handle information, and all memory except for mapped images.
    • Mini - A small dump containing module lists, thread lists, exception information, and all stacks.

    If not specified, Full is the default.

  • -o|--output <output_dump_path>

    The full path and file name where the collected dump should be written. Ensure that the user under which the dotnet process is running has write permissions to the specified directory.

    If not specified:

    • Defaults to .\dump_YYYYMMDD_HHMMSS.dmp on Windows.
    • Defaults to ./core_YYYYMMDD_HHMMSS on Linux and macOS.

    YYYYMMDD is Year/Month/Day and HHMMSS is Hour/Minute/Second.

  • --diag

    Enables dump collection diagnostic logging.

  • --crashreport

    Enables crash report generation.

Note

On Linux and macOS, this command expects the target application and dotnet-dump to share the same TMPDIR environment variable. Otherwise, the command will time out.

Note

To collect a dump using dotnet-dump, it needs to be run as the same user as the user running target process or as root. Otherwise, the tool will fail to establish a connection with the target process.

dotnet-dump analyze

Starts an interactive shell to explore a dump. The shell accepts various SOS commands.

Synopsis

dotnet-dump analyze <dump_path> [-h|--help] [-c|--command]

Arguments

  • <dump_path>

    Specifies the path to the dump file to analyze.

Options

  • -c|--command <debug_command>

    Runs the command on start. Multiple instances of this parameter can be used in an invocation to chain commands. Commands will get run in the order that they are provided on the command line. If you want dotnet dump to exit after the commands, your last command should be 'exit'.

Analyze SOS commands

Command Function
analyzeoom Displays the info of the last OOM that occurred on an allocation request to the GC heap.
clrmodules Lists the managed modules in the process.
clrstack Provides a stack trace of managed code only.
clrthreads Lists the managed threads that are running.
clru Displays an annotated disassembly of a managed method.
d or readmemory Dumps memory contents.
dbgout Enables/disables (-off) internal SOS logging.
dso Displays all managed objects found within the bounds of the current stack.
dumpalc Displays details about a collectible AssemblyLoadContext to which the specified object is loaded.
dumparray Displays details about a managed array.
dumpasync Displays info about async state machines on the garbage-collected heap.
dumpassembly Displays details about an assembly.
dumpclass Displays information about the EEClass structure at the specified address.
dumpconcurrentdictionary Displays concurrent dictionary content.
dumpconcurrentqueue Displays concurrent queue content.
dumpdelegate Displays information about a delegate.
dumpdomain Displays information about the all assemblies within all the AppDomains or the specified one.
dumpgcdata Displays information about the GC data.
dumpgen Displays heap content for the specified generation.
dumpheap Displays info about the garbage-collected heap and collection statistics about objects.
dumpil Displays the common intermediate language (CIL) that's associated with a managed method.
dumplog Writes the contents of an in-memory stress log to the specified file.
dumpmd Displays information about the MethodDesc structure at the specified address.
dumpmodule Displays information about the module at the specified address.
dumpmt Displays information about the method table at the specified address.
dumpobj Displays info the object at the specified address.
dumpruntimetypes Finds all System.RuntimeType objects in the GC heap and prints the type name and MethodTable they refer too.
dumpsig Dumps the signature of a method or field specified by <sigaddr> <moduleaddr>.
dumpsigelem Dumps a single element of a signature object.
dumpstackobjects Displays all managed objects found within the bounds of the current stack.
dumpvc Displays info about the fields of a value class.
eeheap Displays info about process memory consumed by internal runtime data structures.
eestack Runs dumpstack on all threads in the process.
eeversion Displays information about the runtime and SOS versions.
ehinfo Displays the exception handling blocks in a JIT-ed method.
exit or quit Exits interactive mode.
finalizequeue Displays all objects registered for finalization.
findappdomain Attempts to resolve the AppDomain of a GC object.
gchandles Displays statistics about garbage collector handles in the process.
gcheapstat Displays statistics about garbage collector.
gcinfo Displays the JIT GC encoding for a method.
gcroot Displays info about references (or roots) to the object at the specified address.
gcwhere Displays the location in the GC heap of the specified address.
histclear Releases any resources used by the family of Hist commands.
histinit Initializes the SOS structures from the stress log saved in the debuggee.
histobj Examines all stress log relocation records and displays the chain of garbage collection relocations that may have led to the address passed in as an argument.
histobjfind Displays all the log entries that reference the object at the specified address.
histroot Displays information related to both promotions and relocations of the specified root.
histstats Displays stress log stats.
ip2md Displays the MethodDesc structure at the specified address in code that has been JIT-compiled.
listnearobj Displays the object preceding and succeeding the specified address.
logopen Enables console file logging.
logclose Disables console file logging.
logging Enables/disables internal SOS logging.
lm or modules Displays the native modules in the process.
name2ee Displays the MethodTable and EEClass structures for the specified type or method in the specified module.
objsize Displays the size of the specified object.
parallelstacks Displays the merged threads stack similarly to the Visual Studio 'Parallel Stacks' panel.
pathto Displays the GC path from <root> to <target>.
pe or printexception Displays and formats fields of any object derived from the Exception class at the specified address.
r or registers Displays the thread's registers.
runtimes Lists the runtimes in the target or changes the default runtime.
setclrpath Sets the path to load coreclr dac/dbi files using setclrpath <path>.
setsymbolserver Enables the symbol server support.
sos Executes various coreclr debugging commands. Use the syntax sos <command-name> <args>. For more information, see 'soshelp'.
soshelp or help Displays all available commands.
soshelp <command> or help <command> Displays the specified command.
syncblk Displays the SyncBlock holder info.
taskstate Displays a Task state in a human readable format.
threadpool Displays info about the runtime thread pool.
threadpoolqueue Displays queued thread pool work items.
threadstate Pretty prints the meaning of a threads state.
threads <threadid> or setthread <threadid> Sets or displays the current thread ID for the SOS commands.
timerinfo Displays information about running timers.
token2ee Displays the MethodTable structure and MethodDesc structure for the specified token and module.
traverseheap Writes out heap information to a file in a format understood by the CLR Profiler.
verifyheap Checks the GC heap for signs of corruption.
verifyobj Checks the object that is passed as an argument for signs of corruption.

Note

Additional details can be found in SOS Debugging Extension for .NET.

dotnet-dump ps

Lists the dotnet processes that dumps can be collected from. dotnet-dump version 6.0.320703 and later versions also display the command-line arguments that each process was started with, if available.

Synopsis

dotnet-dump ps [-h|--help]

Example

Suppose you start a long-running app using the command dotnet run --configuration Release. In another window, you run the dotnet-dump ps command. The output you'll see is as follows. The command-line arguments, if any, are shown in dotnet-dump version 6.0.320703 and later.

> dotnet-dump ps

  21932 dotnet     C:\Program Files\dotnet\dotnet.exe   run --configuration Release
  36656 dotnet     C:\Program Files\dotnet\dotnet.exe

Using dotnet-dump

The first step is to collect a dump. This step can be skipped if a core dump has already been generated. The operating system or the .NET Core runtime's built-in dump generation feature can each create core dumps.

$ dotnet-dump collect --process-id 1902
Writing minidump to file ./core_20190226_135837
Written 98983936 bytes (24166 pages) to core file
Complete

Now analyze the core dump with the analyze command:

$ dotnet-dump analyze ./core_20190226_135850
Loading core dump: ./core_20190226_135850
Ready to process analysis commands. Type 'help' to list available commands or 'help [command]' to get detailed help on a command.
Type 'quit' or 'exit' to exit the session.
>

This action brings up an interactive session that accepts commands like:

> clrstack
OS Thread Id: 0x573d (0)
    Child SP               IP Call Site
00007FFD28B42C58 00007fb22c1a8ed9 [HelperMethodFrame_PROTECTOBJ: 00007ffd28b42c58] System.RuntimeMethodHandle.InvokeMethod(System.Object, System.Object[], System.Signature, Boolean, Boolean)
00007FFD28B42DD0 00007FB1B1334F67 System.Reflection.RuntimeMethodInfo.Invoke(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo) [/root/coreclr/src/mscorlib/src/System/Reflection/RuntimeMethodInfo.cs @ 472]
00007FFD28B42E20 00007FB1B18D33ED SymbolTestApp.Program.Foo4(System.String) [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 54]
00007FFD28B42ED0 00007FB1B18D2FC4 SymbolTestApp.Program.Foo2(Int32, System.String) [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 29]
00007FFD28B42F00 00007FB1B18D2F5A SymbolTestApp.Program.Foo1(Int32, System.String) [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 24]
00007FFD28B42F30 00007FB1B18D168E SymbolTestApp.Program.Main(System.String[]) [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 19]
00007FFD28B43210 00007fb22aa9cedf [GCFrame: 00007ffd28b43210]
00007FFD28B43610 00007fb22aa9cedf [GCFrame: 00007ffd28b43610]

To see an unhandled exception that killed your app:

> pe -lines
Exception object: 00007fb18c038590
Exception type:   System.Reflection.TargetInvocationException
Message:          Exception has been thrown by the target of an invocation.
InnerException:   System.Exception, Use !PrintException 00007FB18C038368 to see more.
StackTrace (generated):
SP               IP               Function
00007FFD28B42DD0 0000000000000000 System.Private.CoreLib.dll!System.RuntimeMethodHandle.InvokeMethod(System.Object, System.Object[], System.Signature, Boolean, Boolean)
00007FFD28B42DD0 00007FB1B1334F67 System.Private.CoreLib.dll!System.Reflection.RuntimeMethodInfo.Invoke(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo)+0xa7 [/root/coreclr/src/mscorlib/src/System/Reflection/RuntimeMethodInfo.cs @ 472]
00007FFD28B42E20 00007FB1B18D33ED SymbolTestApp.dll!SymbolTestApp.Program.Foo4(System.String)+0x15d [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 54]
00007FFD28B42ED0 00007FB1B18D2FC4 SymbolTestApp.dll!SymbolTestApp.Program.Foo2(Int32, System.String)+0x34 [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 29]
00007FFD28B42F00 00007FB1B18D2F5A SymbolTestApp.dll!SymbolTestApp.Program.Foo1(Int32, System.String)+0x3a [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 24]
00007FFD28B42F30 00007FB1B18D168E SymbolTestApp.dll!SymbolTestApp.Program.Main(System.String[])+0x6e [/home/mikem/builds/SymbolTestApp/SymbolTestApp/SymbolTestApp.cs @ 19]

StackTraceString: <none>
HResult: 80131604

Troubleshooting dump collection issues

Dump collection requires the process to be able to call ptrace. If you are facing issues collecting dumps, the environment you are running on may be configured to restrict such calls. See our Dumps: FAQ for troubleshooting tips and potential solutions to common issues.

See also