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Tools Available for Debugging & Analysis
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<small>''(Updated: Feb 2010)''</small>
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__TOC__
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A variety of diagnostic and analysis tools are available to debug issues with the Lustre™ software. Some of these are provided in Linux distributions, while others have been developed and are made available by the Lustre project.
  
There are several diagnostic tools available to debug Lustre; some are provided by the operating system, while others were developed and made available by the Lustre project.
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== Lustre Debugging Tools ==
  
= Lustre Debugging Tools =
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The following in-kernel debug mechanisms are incorporated into the Lustre software:
  
==In-kernel debug mechanisms ==
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* '''Debug logs.''' A circular debug buffer to which Lustre internal [[Lustre_Debugging_Procedures#Understanding_the_Lustre_debug_messaging_format|debug messages]] are written (in contrast to error messages, which are printed to the syslog or console). Entries to the Lustre debug log are controlled by the mask set by ''/proc/sys/lnet/debug''. The log size defaults to 5 MB per CPU but can be increased as a busy system will quickly overwrite 5 MB. When the buffer fills, the oldest information is discarded.
  
* debug logs: When a kernel module is first inserted, a circular debug buffer is allocated to hold substantial amount of debugging information (in megabytes or more). When the buffer fills up, it wraps around and discards the oldest information. We have added debug messages specifically for Lustre; they can be written out to this kernel log.
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* '''Debug daemon.''' The debug daemon controls logging of debug messages.
* debug daemon: The debug daemon provides the facility for unlimited logging of the CDEBUG logs in Lustre.
 
* /proc/sys/lnet/debug: Contains a mask that can be used to delimit the debugging information written out to the kernel debug logs.  
 
  
==Other internal tools==
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* '''''/proc/sys/lnet/debug''.''' This file contains a mask that can be used to delimit the debugging information written out to the kernel debug logs.  
* lctl: This tool is made available by Lustre. It is very useful to filter the kernel and extract useful information.
 
* Lustre subsystem asserts: In case of asserts, a log will be written out to /tmp/lustre_log.<timestamp>.
 
* lfs: A Lustre utility that can be used to get to a Lustre file's extended attributes (among other things).
 
  
=External debugging tools for administrators and developers=
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For more information about using these tools to debug Lustre issues, see [[Lustre Debugging Procedures]].
  
* strace: Allows Lustre users to trace a system call.
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These tools are also provided with the Lustre software:
* /var/log/messages: The directory to which fatal or serious messages are printed by the syslogd.
 
* Crash dumps: On some kernels, a sysrq "c" is enabled which produces a crash dump. Lustre enhances this crash dump with a log dump (the last 64K of log) to the console.
 
* debugfs: An nteractive Ext2 filesystem debugger.
 
'''Logging and data collection tools'''
 
These logging and data collection tools can be used to collect information for debugging Lustre kernel issues.
 
  
==== kdump ====
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* '''lctl.''' This tool is used with the ''debug_kernel'' option to manually dump the Lustre debugging log or post-process debugging logs that are dumped automatically. For more information about the ''lctl'' tool, see [http://wiki.lustre.org/manual/LustreManual20_HTML/LustreDebugging.html#50438274_pgfId-1295889 Section 28.2.2: ''Using the lctl Tool to View Debug Messages''] and [http://wiki.lustre.org/manual/LustreManual20_HTML/SystemConfigurationUtilities_HTML.html#50438219_pgfId-1318224 Section 36.3: ''lctl''] in the [http://wiki.lustre.org/manual/LustreManual20_HTML/index.html ''Lustre Operations Manual''].
''kdump'' is a Linux kernel crash utility useful for debugging a system running Red Hat Enterprise Linux. For more information about ''kdump'', see the Red Hat knowledge base article [http://kbase.redhat.com/faq/docs/DOC-6039 ''How do I configure kexec/kdump on Red Hat Enterprise Linux 5?'']. To download ''kdump'', go to the [http://fedoraproject.org/wiki/SystemConfig/kdump#Download Fedora Project Download] site.
 
  
==== netdump ====
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* '''Lustre subsystem asserts.''' A panic-style assertion (LBUG) in the kernel causes Lustre to dump the debug log to the file ''/tmp/lustre-log.<timestamp>'' where it can be retrieved after a reboot. For more information, see [http://wiki.lustre.org/manual/LustreManual20_HTML/LustreTroubleshooting.html#50438198_pgfId-1291324 Section 26.1.2: ''Viewing Error Messages''] in the [http://wiki.lustre.org/manual/LustreManual20_HTML/index.html ''Lustre Operations Manual'']
''netdump'' is a crash dump utility from Red Hat that allows memory images to be dumped over a network to a central server for analysis. [[It is now obsolete and has been replaced by kdump. Check this]]
 
  
==== netconsole ====
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* '''lfs.''' This utility provides access to the extended attributes (EAs) of a Lustre file (along with other information). For more information about ''lfs'', see [http://wiki.lustre.org/manual/LustreManual20_HTML/UserUtilities_HTML.html#50438206_pgfId-1305210 Section 32.1: lfs] in the [http://wiki.lustre.org/manual/LustreManual20_HTML/index.html ''Lustre Operations Manual''].
''netconsole'' supports kernel-level network logging over UDP. A system requires (''SysRq'') allows users to collect relevant data through ''netconsole''. For more information, see [[Netconsole|Netconsole]].
 
  
==== [[lctl]] ====
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== External debugging tools ==
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====Tools for administrators and developers ====
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The tools described in this section are provided in the Linux kernel or are available at an external website. For information about using some of these tools for Lustre debugging, see [[Lustre Debugging Procedures]] and [[Lustre Debugging for Developers]].
  
[[lctl used with the debug_kernel option dumps the lustre debugging log]]
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Some general debugging tools provided as a part of the standard Linux distro are:
  
=Additional external debugging and analysis tools for developers=
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* '''strace.''' This tool allows a system call to be traced.
  
* leak_finder.pl: An extremely useful program that helps locate memory leaks in the code.
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* '''''/var/log/messages'''.'' ''syslogd'' prints fatal or serious messages at this log.
The tools described below may be useful for debugging Lustre™ in a development environment.
 
  
=== Virtual Machines ===
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* '''Crash dumps.''' On crash-dump enabled kernels, ''sysrq c'' produces a crash dump. Lustre enhances this crash dump with a log dump (the last 64 KB of the log) to the console.
A virtual machine is often used to create an isolated development and test environment.
 
  
==== VirtualBox ====
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* '''debugfs.''' Interactive file system debugger.
VirtualBox Open Source Edition provides enterprise-class virtualization capability for all major platforms and is available free from Sun Microsystems at [http://www.sun.com/software/products/virtualbox/get.jsp?intcmp=2945 Get Sun Virtual Box].
 
  
==== VMware Server ====
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The following ''logging and data collection tools'' can be used to collect information for debugging Lustre kernel issues:  
The VMware Server virtualization platform is available as free introductory software at [http://downloads.vmware.com/d/info/datacenter_downloads/vmware_server/2_0 Download VMware Server].
 
  
==== Xen ====
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* '''kdump.''' A Linux kernel crash utility useful for debugging a system running Red Hat Enterprise Linux. For more information about ''kdump'', see the Red Hat knowledge base article [http://kbase.redhat.com/faq/docs/DOC-6039 ''How do I configure kexec/kdump on Red Hat Enterprise Linux 5?'']. To download ''kdump'', go to the [http://fedoraproject.org/wiki/SystemConfig/kdump#Download Fedora Project Download] site.
  
Xen is a para-virtualized environment with virtualization capabilities similar to VMware Server and Virtual Box. However, Xen allows the use of modified kernels to provide near-native performance and the ability to emulate shared storage. For more information, see [[Using Xen with Lustre]]. [[link to xen.org]]
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* '''netconsole.''' Supports kernel-level network logging over UDP. A system requires (''SysRq'') allows users to collect relevant data through ''netconsole''. For more information, see [[Netconsole|Netconsole]].  
  
== Debuggers and Analysis Tools ==
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* '''netdump.''' A crash dump utility from Red Hat that allows memory images to be dumped over a network to a central server for analysis. The ''netdump'' utility was replaced by ''kdump'' in RHEL 5. For more information about ''netdump'', see [http://www.redhat.com/support/wpapers/redhat/netdump/ ''Red Hat, Inc.'s Network Console and Crash Dump Facility''].
==== kgdb ====
 
''kgdb'' is a source-level kernel debugger that allows remote debugging using ''conman''.  
 
  
kgdb provides a special set of hooks for a Linux kernel to attach ''gdb'' from another machine over a serial console. We provide ''kgdb'' patches for some kernels like ''rhel4'' with the Lustre patches (these are not patched in by default).
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==== Tools for developers ====
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The tools described in this section may be useful for debugging Lustre™ in a development environment.
  
For more information, see [[KGDB]]
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Of general interest is:
and [[Using kgdb with UDP]].
 
  
Also see [http://www.linuxtopia.org/online_books/redhat_linux_debugging_with_gdb/running.html ''Chapter 6. Running Programs Under gdb''] in the ''Red Hat Linux 4 Debugging with GDB'' guide.
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* '''leak_finder.pl.''' This program provided with Lustre is useful for finding memory leaks in the code.
  
==== [[lcrash]] ====
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A ''virtual machine'' is often used to create an isolated development and test environment. Some commonly-used virtual machines are:
[[lcrash - Linux crash dump analyzer]] generic Linux tool - find link
 
  
==== crash ====
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* '''VirtualBox Open Source Edition.''' Provides enterprise-class virtualization capability for all major platforms and is available free from Sun Microsystems at [http://www.sun.com/software/products/virtualbox/get.jsp?intcmp=2945 Get Sun Virtual Box].
''crash'' is used to analyze saved crash dump data.
 
  
Enter:
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* '''VMware Server.''' Virtualization platform available as free introductory software at [http://downloads.vmware.com/d/info/datacenter_downloads/vmware_server/2_0 Download VMware Server].
crash vmlinux crash_dump
 
  
For more information about using ''crash'' to analyze crash dump output, see:
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* '''Xen.''' A para-virtualized environment with virtualization capabilities similar to VMware Server and Virtual Box. However, Xen allows the use of modified kernels to provide near-native performance and the ability to emulate shared storage. For more information, see [[Using Xen with Lustre]] or go to [http://xen.org xen.org]
  
* Red Hat Magazine article [http://magazine.redhat.com/2007/08/15/a-quick-overview-of-linux-kernel-crash-dump-analysis/ ''A quick overview of Linux kernel crash dump analysis''].
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A variety of ''debuggers and analysis tools'' are available including:
* [http://people.redhat.com/anderson/crash_whitepaper/#EXAMPLES Crash Usage: A Case Study] from the white paper ''Red Hat Crash Utility'' by David Anderson.
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*Kernel Trap forum entry [http://kerneltrap.org/node/5758 Linux: Kernel Crash Dumps].
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* '''kgdb.''' The Linux Kernel Source Level Debugger ''kgdb'' is used in conjunction with the GNU Debugger ''gdb'' for debugging the Linux kernel. For more information about using ''kgdb'' with gdb, see [http://www.linuxtopia.org/online_books/redhat_linux_debugging_with_gdb/running.html ''Chapter 6. Running Programs Under gdb''] in the ''Red Hat Linux 4 Debugging with GDB'' guide.
* White paper [http://www.google.com/url?sa=t&source=web&ct=res&cd=8&ved=0CCUQFjAH&url=http%3A%2F%2Fwww.kernel.sg%2Fpapers%2Fcrash-dump-analysis.pdf&rct=j&q=redhat+crash+dump&ei=6aQBS-ifK4T8tAPcjdiHCw&usg=AFQjCNEk03E3GDtAsawG3gfpwc1gGNELAg ''A Quick Overview of Linux Kernel Crash Dump Analysis''].
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* '''crash.''' Used to analyze saved crash dump data when a system had panicked or locked up or appears unresponsive. For more information about using ''crash'' to analyze a crash dump, see:
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: - Red Hat Magazine article [http://magazine.redhat.com/2007/08/15/a-quick-overview-of-linux-kernel-crash-dump-analysis/ ''A quick overview of Linux kernel crash dump analysis''].
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: - [http://people.redhat.com/anderson/crash_whitepaper/#EXAMPLES Crash Usage: A Case Study] from the white paper ''Red Hat Crash Utility'' by David Anderson.
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: - Kernel Trap forum entry [http://kerneltrap.org/node/5758 Linux: Kernel Crash Dumps].
 +
: - White paper [http://www.google.com/url?sa=t&source=web&ct=res&cd=8&ved=0CCUQFjAH&url=http%3A%2F%2Fwww.kernel.sg%2Fpapers%2Fcrash-dump-analysis.pdf&rct=j&q=redhat+crash+dump&ei=6aQBS-ifK4T8tAPcjdiHCw&usg=AFQjCNEk03E3GDtAsawG3gfpwc1gGNELAg ''A Quick Overview of Linux Kernel Crash Dump Analysis''].

Latest revision as of 07:53, 20 January 2011

(Updated: Feb 2010)

A variety of diagnostic and analysis tools are available to debug issues with the Lustre™ software. Some of these are provided in Linux distributions, while others have been developed and are made available by the Lustre project.

Lustre Debugging Tools

The following in-kernel debug mechanisms are incorporated into the Lustre software:

  • Debug logs. A circular debug buffer to which Lustre internal debug messages are written (in contrast to error messages, which are printed to the syslog or console). Entries to the Lustre debug log are controlled by the mask set by /proc/sys/lnet/debug. The log size defaults to 5 MB per CPU but can be increased as a busy system will quickly overwrite 5 MB. When the buffer fills, the oldest information is discarded.
  • Debug daemon. The debug daemon controls logging of debug messages.
  • /proc/sys/lnet/debug. This file contains a mask that can be used to delimit the debugging information written out to the kernel debug logs.

For more information about using these tools to debug Lustre issues, see Lustre Debugging Procedures.

These tools are also provided with the Lustre software:

External debugging tools

Tools for administrators and developers

The tools described in this section are provided in the Linux kernel or are available at an external website. For information about using some of these tools for Lustre debugging, see Lustre Debugging Procedures and Lustre Debugging for Developers.

Some general debugging tools provided as a part of the standard Linux distro are:

  • strace. This tool allows a system call to be traced.
  • /var/log/messages. syslogd prints fatal or serious messages at this log.
  • Crash dumps. On crash-dump enabled kernels, sysrq c produces a crash dump. Lustre enhances this crash dump with a log dump (the last 64 KB of the log) to the console.
  • debugfs. Interactive file system debugger.

The following logging and data collection tools can be used to collect information for debugging Lustre kernel issues:

  • netconsole. Supports kernel-level network logging over UDP. A system requires (SysRq) allows users to collect relevant data through netconsole. For more information, see Netconsole.
  • netdump. A crash dump utility from Red Hat that allows memory images to be dumped over a network to a central server for analysis. The netdump utility was replaced by kdump in RHEL 5. For more information about netdump, see Red Hat, Inc.'s Network Console and Crash Dump Facility.

Tools for developers

The tools described in this section may be useful for debugging Lustre™ in a development environment.

Of general interest is:

  • leak_finder.pl. This program provided with Lustre is useful for finding memory leaks in the code.

A virtual machine is often used to create an isolated development and test environment. Some commonly-used virtual machines are:

  • VirtualBox Open Source Edition. Provides enterprise-class virtualization capability for all major platforms and is available free from Sun Microsystems at Get Sun Virtual Box.
  • Xen. A para-virtualized environment with virtualization capabilities similar to VMware Server and Virtual Box. However, Xen allows the use of modified kernels to provide near-native performance and the ability to emulate shared storage. For more information, see Using Xen with Lustre or go to xen.org

A variety of debuggers and analysis tools are available including:

  • kgdb. The Linux Kernel Source Level Debugger kgdb is used in conjunction with the GNU Debugger gdb for debugging the Linux kernel. For more information about using kgdb with gdb, see Chapter 6. Running Programs Under gdb in the Red Hat Linux 4 Debugging with GDB guide.
  • crash. Used to analyze saved crash dump data when a system had panicked or locked up or appears unresponsive. For more information about using crash to analyze a crash dump, see:
- Red Hat Magazine article A quick overview of Linux kernel crash dump analysis.
- Crash Usage: A Case Study from the white paper Red Hat Crash Utility by David Anderson.
- Kernel Trap forum entry Linux: Kernel Crash Dumps.
- White paper A Quick Overview of Linux Kernel Crash Dump Analysis.