Dump collection and analysis utility (dotnet-dump)
- 5 minutes to read
This article applies to: ✔️ .NET Core 3.0 SDK and later versions
Note
dotnet-dump isn't supported on macOS.
Installing dotnet-dump
To install the latest release version of the dotnet-dump NuGet package, use the dotnet tool install command:
dotnet tool install -g dotnet-dump
Synopsis
dotnet-dump [-h|--help] [--version] <command>
Description
The dotnet-dump global tool is a way to collect and analyze Windows and Linux dumps without any native debugger involved like lldb on Linux. 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
--versionDisplays the version of the dotnet-dump utility.
-h|--helpShows command-line help.
Commands
| Command |
|---|
| dotnet-dump collect |
| dotnet-dump analyze |
dotnet-dump collect
Captures a dump from a process.
Synopsis
dotnet-dump collect [-h|--help] [-p|--process-id] [--type] [-o|--output] [--diag]
Options
-h|--helpShows command-line help.
-p|--process-id <PID>Specifies the process ID number to collect a memory dump from.
--type <Heap|Mini>Specifies the dump type, which determines the kinds of information that are collected from the process. There are two types:
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,
Heapis the default.-o|--output <output_dump_path>The full path and file name where the collected dump should be written.
If not specified:
- Defaults to .\dump_YYYYMMDD_HHMMSS.dmp on Windows.
- Defaults to ./core_YYYYMMDD_HHMMSS on Linux.
YYYYMMDD is Year/Month/Day and HHMMSS is Hour/Minute/Second.
--diagEnables dump collection diagnostic logging.
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>Specifies the command to run in the shell on start.
Analyze SOS commands
| Command | Function |
|---|---|
soshelp |
Displays all available commands |
soshelp|help <command> |
Displays the specified command. |
exit|quit |
Exits interactive mode. |
clrstack <arguments> |
Provides a stack trace of managed code only. |
clrthreads <arguments> |
Lists the managed threads running. |
dumpasync <arguments> |
Displays information about async state machines on the garbage-collected heap. |
dumpassembly <arguments> |
Displays details about an assembly. |
dumpclass <arguments> |
Displays information about a EE class structure at the specified address. |
dumpdelegate <arguments> |
Displays information about a delegate. |
dumpdomain <arguments> |
Displays information all the AppDomains and all assemblies within the domains. |
dumpheap <arguments> |
Displays info about the garbage-collected heap and collection statistics about objects. |
dumpil <arguments> |
Displays the Microsoft intermediate language (MSIL) that is associated with a managed method. |
dumplog <arguments> |
Writes the contents of an in-memory stress log to the specified file. |
dumpmd <arguments> |
Displays information about a MethodDesc structure at the specified address. |
dumpmodule <arguments> |
Displays information about a EE module structure at the specified address. |
dumpmt <arguments> |
Displays information about a method table at the specified address. |
dumpobj <arguments> |
Displays info about an object at the specified address. |
dso|dumpstackobjects <arguments> |
Displays all managed objects found within the bounds of the current stack. |
eeheap <arguments> |
Displays info about process memory consumed by internal runtime data structures. |
finalizequeue <arguments> |
Displays all objects registered for finalization. |
gcroot <arguments> |
Displays info about references (or roots) to an object at the specified address. |
gcwhere <arguments> |
Displays the location in the GC heap of the argument passed in. |
ip2md <arguments> |
Displays the MethodDesc structure at the specified address in JIT code. |
histclear <arguments> |
Releases any resources used by the family of hist* commands. |
histinit <arguments> |
Initializes the SOS structures from the stress log saved in the debuggee. |
histobj <arguments> |
Displays the garbage collection stress log relocations related to <arguments>. |
histobjfind <arguments> |
Displays all the log entries that reference an object at the specified address. |
histroot <arguments> |
Displays information related to both promotions and relocations of the specified root. |
lm|modules |
Displays the native modules in the process. |
name2ee <arguments> |
Displays the MethodTable structure and EEClass structure for the <argument>. |
pe|printexception <arguments> |
Displays any object derived from the Exception class at the address <argument>. |
setsymbolserver <arguments> |
Enables the symbol server support |
syncblk <arguments> |
Displays the SyncBlock holder info. |
threads|setthread <threadid> |
Sets or displays the current thread ID for the SOS commands. |
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
Special instructions for Docker
If you're running under Docker, dump collection requires SYS_PTRACE capabilities (--cap-add=SYS_PTRACE or --privileged).
On Microsoft .NET Core SDK Linux Docker images, some dotnet-dump commands can throw the following exception:
Unhandled exception: System.DllNotFoundException: Unable to load shared library 'libdl.so' or one of its dependencies' exception.
To work around this problem, install the "libc6-dev" package.