Abstract:
A common interface (API) is provided which permits a single diagnostic probe manager to communicate with and to control a plurality of diagnostic probes. Through this interface the diagnostic probes are enabled to pass information concerning dependencies between software levels present in a hierarchical stack. This information is particularly useful in that it permits the probe manager to direct diagnostic efforts at the lowest desirable level so as to avoid the problems that occur when problems are indicated at a high level but which are actually caused by lower level software components.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is generally directed to diagnosing software problems in data processing systems. More particularly, the present invention is particularly directed to a system and method for consistent and extendable management of diagnostic probes. Even more particularly the present invention is directed to a system of independently constructable diagnostic probes. And even more particularly, the present invention is directed to the construction and utilization of diagnostic software probes which are capable of diagnosing problems within a plurality of system software levels. Moreover, the present invention is particularly useful in clustered data processing systems which generally possess more complex software in a distributed hierarchical arrangement. 
     In the context of the present invention, a diagnostic probe is a relatively small, stand-alone program that provides direct diagnostic functionality for a specific software or hardware component in a data processing system. Each probe is capable of codifying a specific part of an expert&#39;s debugging knowledge. 
     In cluster systems management software, many components and daemons run on many machines (nodes) and these components are designed so that normally they are communicating properly and using correct data in order for the cluster to run properly. However, it is difficult to guarantee that all of these various components can automatically recover from communication and data integrity problems. Thus, there may be times when some portion of the cluster stops functioning properly. Making the problem worse, it is usually very difficult for the customer to diagnose the root cause of these problems because of the complexity of the components and the various interactions which are designed into the system to insure that the components work together efficiently, consistently and harmoniously. This complexity is enhanced by the fact that software is often configured in a hierarchy of levels and dependencies. A problem at a low level may manifest itself at a higher level but diagnosis at the higher level may not provide any clues as to the nature of the dysfunction. 
     The diagnostic probe manager system of the present invention assists customers in diagnosing software problems in the cluster. The invention includes a probe manager and a plurality of probes. Each probe preferably checks only one system component to verify that it is functioning properly and that it has appropriate data. In addition, each probe returns an indication of the other probes it is dependent on. This indication usually identifies the probes of other, possibly related components that should be working properly in order for this probe&#39;s component to work. The probe manager queries all the probes that are registered for their specific dependencies. The probes use this information to build a dependency graph so that it can run the probes in order from the lowest software layer to the highest layer. This increases the chances of finding the root cause of the problem, instead of merely finding downstream effects. When a probe finds a problem, it displays the problem (and usually a corrective action) to the user, and the default action of the probe manager is to stop. It is noted that the operation of the diagnostic probes herein does not necessarily have to take place because of or be driven by the occurrence of a problem or fault. The probe manager is capable of initiating probe activity on its own, based on a number of criteria including scheduled maintenance intervals. Furthermore, the probe manager is aware of the fact that certain portions of the data processing system and its related software are more important than others. Accordingly, probes are supplied that examine many of the critical aspects of the operating system as well as many components of cluster systems management software, particularly those that are known to have greater significance in maintaining system operations. 
     The real value of this diagnostic probe manager subsystem is that the software vendor (in this case International Business Machines, Inc., the assignee of the present invention) is better able to codify its expertise in diagnosing the software, thus contributing to an accumulation of knowledge relevant to how all the components fit together, what things typically go wrong, and the order in which things should be examined. It is like having the smartest developer of the software come to your site and sit down and start looking at the pieces of the software in the most logical order, checking for all the things the software developer has seen go wrong until the problem is found. 
     Most currently available software diagnostic tools are either structured as a single program or they include a set of hard-coded tools that try to diagnose system problems. These diagnostic tools typically diagnose the operating system of only a single personal computer or workstation. In a data processing system which includes a plurality of independent nodes operating and intercommunicating in a clustered environment, the situation is much more complex. Not only can things go wrong at the operating system level, but the whole cluster software stack can have problems, and multiple machines are involved. As used herein the phrase “software stack” refers to a collection of programs which run below the level of application programs and which exist in a hierarchical arrangement of operational and data dependencies. To tackle diagnosing a system as complex as this, a flexible, extensible, easy to develop solution provides the most highly desired solution. 
     The architecture of the probe system allows each probe to be developed individually, by separate people. In the typical situation, an expert on a particular component develops the probe for that component. Several utilities are provided for implementing probes so that the probe developer can concentrate on just the things that can go wrong with that component. Because dependent probes are executed first, the scope of what can go wrong with a component is limited to things specific to that component. In contrast, a monolithic diagnostic program responsible for checking the whole software stack quickly becomes so complicated that component experts usually can&#39;t develop it. Instead, it usually requires developers that are dedicated to working on the diagnostic tool. However, the probe architecture of the present invention allows development of probes in a decentralized fashion. 
     Another issue with diagnostic tools is coverage. A diagnostic tool is most useful if it catches a high percentage of users&#39; problems. In the present invention the dependency processing feature and separation of probes allows additional probes to be added over time; in this manner, the coverage is increased and newly added software components are provided with diagnostic coverage. Additionally, newly discovered problems are easily be added to the diagnostic probes. 
     Another important feature of the architecture of the present probe subsystem is that it can be extended by customers. The probe utilities and the Application Program Interface (API) between the probe manager and the probes permits customers to add their own probes. This allows customers to diagnose applications that they run on top of the clustering software and also allows them to check for errors that they have encountered that supplied probes don&#39;t yet catch. 
     SUMMARY OF THE INVENTION 
     In accordance with a preferred embodiment of the present invention a method is provided for diagnosing software problems in data processing systems comprising the step of providing a common interface for communicating with a plurality of diagnostic probes. A diagnostic probe manager is employed which provides a common interface for launching (if necessary) and for communicating with a plurality of independent diagnostic probes which are capable of returning information regarding dependency. The probes are preferably focused on a single software component whose dependency level is either known or communicated. 
     Accordingly, it is an object of the present invention to provide diagnoses of software problems, particularly in clustered data processing systems. 
     It is also an object of the present invention to increase the reliability of data processing systems, particularly clustered data processing systems. 
     It is a still further object of the present invention to provide diagnostic probes which are directed to specific software components. 
     Additionally, it is an object of the present invention to provide a common and consistent interface which permits independently created diagnostic probes to interact with a diagnostic probe manager. 
     It is yet another object of the present invention to permit the creation of diagnostic probes which are directed at specific levels of software dependencies. 
     It is another object of the present invention to provide diagnostic probes which are able to communicate dependency information. 
     It is a still further object of the present invention to provide a manager for a plurality of diagnostic probes. 
     It is also an object of the present invention to provide an interface and environment for the creation of independently written diagnostic probes. 
     It is yet another object of the present invention to develop more advanced diagnostic probes. 
     It is an additional object of the present invention to better match diagnostic probes with specifically targeted software components. 
     It is a still further object of the present invention to increase the coverage provided by diagnostic software. 
     It is a still further object of the present invention to provide a mechanism for the consistent development and usage of diagnostic probes for newly discovered problems. 
     It is yet another object of the present invention to provide an environment and an interface which permits individual customers to create their own diagnostic probes. 
     It is also an object of the present invention to provide a mechanism in which software problems can be diagnosed at a more appropriate level which takes dependencies into account. 
     It is a still further object of the present invention to provide a mechanism for the decentralized creation of diagnostic probes. 
     It is an additional object of the present invention to provide a diagnostic probe system which is capable of supplying more germane messages to data processing system users and administrators. 
     It is yet another object of the present invention to provide diagnostic probes which are directed to the analysis of problems associated with a single software component so as to provide more focused analysis, diagnostics and messages. 
     Lastly, but not limited hereto, it is an object of the present invention to provide an architecture and interface for the management, construction, deployment and operation of a plurality of independently operating diagnostic probes. 
     The recitation herein of a list of desirable objects which are met by various embodiments of the present invention is not meant to imply or suggest that any or all of these objects are present as essential features, either individually or collectively, in the most general embodiment of the present invention or in any of its more specific embodiments. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of practice, together with the further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  is a diagram illustrating diagnostic probe dependencies which exist in a tree structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Diagnostic Probe Architecture Overview 
     The diagnostic probe architecture of the present invention provides system administrators with the ability to identify the root cause of system problems. The diagnostic probe architecture includes a probe manager and a set of diagnostic probes and also very preferably includes a sufficiently well defined interface that provides support for creating additional probes. 
     The probe manager is responsible for building a dependency tree of probes and for running the probes based on their position in the tree, from the bottom of the tree to the top of the tree and is also responsible for returning probe results to the system administrator. 
     The diagnostic probes of the present invention are relatively small, stand-alone programs that provide the actual diagnostic functionality relevant to a specific part of a system. Each probe is responsible for checking the health of a subsystem or part of a subsystem. Probes are usually invoked by the probe manager, not by the end user. Upon invocation, each probe is responsible for determining the “health” of a particular part of the system and reporting its findings back to the probe manager. Since components usually depend on other components, a probe for a component is provided with the ability to express dependency on probes for dependent components. 
     The architecture of the diagnostic probe system herein also provides templates and utilities which can be used by component or subsystem developers and system administrators for easily creating new probes. 
     EXTERNALS 
     Introduction 
     The diagnostic probe architecture includes a probe manager and a set of diagnostic probes and is very preferably designed to provide support for creating additional probes which may be customized and specialized to address any number of software subsystems. The external design details of the components associated with the diagnostic probe architecture are discussed in this section. 
     Probe Manager 
     The probe manager uses a dependency list, which is returned by each of the individual diagnostic probes, to build a dependency tree and then executes the probes starting from the leaves of the tree to the root of the tree and then returns the probe result to the system administrator. By executing the probes from the lowest level to the highest level, the root cause of a software/system problem is thereby more easily determined thus avoiding the occurrence of downstream effects. It is noted that in some cases the dependency list may contain a null entry indicating that, for that particular probe, directed to a particular subsystem, there are no immediate dependencies beyond the initial probe itself. 
     As an example, consider a set of Probes A, B, C and D. Suppose that the probes&#39; dependencies are as follows:
         A [Depends on] B   B [Depends on] C, D
 
The order in which these probes are run, with the above dependencies, is as follows:
   Run C &amp; D (Specific order not deterministic)   Run B   Run A       

     Typical Dependency Tree 
       FIG. 1  illustrates a typical set of diagnostic probe dependencies. For example, it is seen that higher level application probes P 1  and P 2  are dependent upon probes P 3  and P 4  (for probe P 1 ) and on probes P 5  and P 6  (for probe P 2 ). Likewise, probe P 3  is dependent on probe P 7  and probe P 8 , and so on, as shown. In operation, probes P 7 , P 8 , P 9 , P 10  and P 11  would be run first and would return their results to probes P 3 , P 4 , P 5  and P 6  in the manner set forth in  FIG. 1 . In this regard it is noted that the probes do not call each other directly; rather, individual probes provide an indication of their dependency other probes. The Probe Manager takes care of running the probes in the correct order and also takes care of ensuring that the same probe does not get run more than once. Also there are no messages that get passed between the probes; each probe performs its task independently of the other probes. 
     In normal operation, any error detected by a probe causes the probe manager to stop executing the probes that depend on the failed probe, thus isolating the problem in a component to the realm of items checked by the failed probe. The probe manager is provided with an option which allows execution of probes that depend on a failed probe. This option is specified by the system administrator when invoking the probe manager command. A probe-to-probe-manager interface is defined and the interaction between the probe and the probe manager is through this interface. 
     Probe Manager Invocation 
     The probe manager command (ProbeManager) provides options to indicate what severity of error messages should be returned, whether it should continue when an error is found, what probes should be run or excluded, etc. These options are also specifiable in a more persistent fashion via environment variables. 
     Probes 
     Probes are small stand-alone programs that provide the actual diagnostic functionality for a specific aspect of a component. Every significant piece of software or system is normally composed of a number of parts that do a specific task and interact with each other to provide a significant function. The parts are referred to components. Each diagnostic probe performs a specific diagnostic task and specifies a list of probes upon which it is dependent. As an example, a probe checking the health of a network daemon (server) will check some specific characteristic of the daemon and could express a dependency on a probe that checks the health of the network. Each component is preferably associated with its own set of probes, with each probe being capable of diagnosing a particular aspect of the component and expressing dependencies on other probes. These other probes either belong to the subject component&#39;s probe set or belong to probes associated with other components outside of the first set of probes. 
     Probe Invocation 
     In accordance with a preferred implementation of the present invention each diagnostic probe support employs a command line invocation such as the preferred one shown below:
         probe-name [-d|-s|-h|-m|[-e msgnum . . . ][-l{1|2|3|4}]]
 
Diagnostic probe options are shown between the square brackets above. In particular, they have the following meanings:
   -h means “show usage information.”   -d means “return the probe dependency list. The probe can specify a required set of dependencies and an optional set of dependencies as well.   -s means “return a one line summary of the purpose of the probe.”   -m means “return a detailed documentation for the probe.”   -e msgnum 1 ,msgnum 2 , . . .
           Indicates that the messages identified by the passed message numbers are to be ignored. They are therefor not output. The probe itself determines whether ignoring the message should affect the exit status or not.   
           -l{1|2|3|4}
           Indicates the level of message output that is to be reported by the probe. The message level determines the urgency of the message. The following message levels are available in preferred embodiments of the present invention:
               1—Show probe trace messages, probe explanation and suggested action messages, probe attention messages and probe error messages. This is the equivalent of a verbose option.   2—Show probe explanation and suggested action messages, probe attention (warning or information) messages and probe error messages.   3—Show probe attention messages and probe error messages only.   4—Show probe error messages only.   
               
               

     Probe Output 
     Output from probes is provided in the form of dependency lists, messages, purpose summary or detailed documentation. An optional status code can also be provided upon return. 
     Dependency List 
     If the probe is given the -d option, the probe simply outputs its list of dependencies to stdout (the standard output file or device as defined to the operating system by or for the system administrator). The list is a colon-separated list of probe names. 
     Messages 
     Each message contains the following information: 
                                                                                                               Probe name       Message level       Message number (Not needed for Trace messages) and       Message text                The message text format is “Probe-name:message-level: message                number: message text.”                -- Probe-name is the name of the probe            -- Message level is one of Trace, Attention, Error or                InternalError indicating the message type.           Trace - trace message used mostly for debugging.           Attention - Warning or Informational message.           Error - Failure message.           InternalError - The probe could not perform the                check because of an internal problem with           the probe.            -- Message number (which is unique) identifying the message.                The message number is not needed for Trace messages.            -- Message text is the text that describes the message being output.                    
Purpose Summary
 
     If the probe is given the -s option, the probe outputs a one line summary about the purpose of the probe. 
     If the probe is given the -h option, the probe outputs usage information, which typically includes information on using the command, including the meaning and structure for all of the valid arguments that are passed to the command. 
     Detailed Documentation 
     If the probe is started with the -m option set, the probe outputs detailed documentation for the probe including such items as exactly how a probe goes about its task of identifying problems. 
     Status Codes 
     When a probe exits, it returns one of five exit status codes to indicate its level of success:
         0—Success—The probe found nothing wrong with the subsystem that it was checking.   1—Invalid—The software component that the probe is checking is not installed or the probe is not valid for the current hardware/software environment. This is not an error and will be ignored by the probe manager.   10—Attention—The probe found some things that must be brought to the attention of the system administrators; but no errors were detected.   20—Error—The probe found an error in the subsystem that it was checking.   127—Internal Error—The probe could not complete its check because an unexpected error occurred while the diagnostics were run.       

     Writing Probes 
     In order to achieve the greatest level of success for the present probe manager architecture, an abundance of probes should be available to most fully address the needs of end users but which of practical needs ought to be provided by component and subsystem developers who are most familiar with their own software. The system administrator should also be able to add new probes easily to identify problems for which probes do not currently exist. Thus the process of diagnostic probe creation should be easy and flexible. Accordingly, the following are important aspects to consider with regard to the task of probe development: (1) Probes are stand-alone programs that communicate with the probe manager using a well-defined interface; (2) The probe manager invokes the probes with certain command line flags and options; (3) The user may have set certain environment variables which the probe should check; (4) The probe communicates back to the probe manager by printing messages to stdout and appropriately setting its exit status; (5) Probes should be intelligent and along with the probe manager simulate the way an expert administrator systematically checks various parts of the system to find the root cause of a problem; (6) Each probe codifies a specific part of this debugging knowledge; (7) Probes scope is small (If the scope of the probes diagnostics are limited, the administrator can be brought very close to the root cause of a failure.); (8) A probe only lists direct dependencies in its dependency list; (9) Probes are preferably conventional executables such as shell scripts, Perl scripts, and statically linked compiled executables. 
     The naming of probes is also providable in a consistent manner. For example, a probe name preferably comprises three components (say company name, product name and probe) specified in the following format (the choice of delimiter being somewhat arbitrary):
         CompanyName.Product.probename
 
An example of a probename in this format is as follows:
   IBM.DMSRM.checkCSMDBUserIdExist       

     If the probe is given the -d option, the probe simply outputs its list of dependencies to stdout. This list is a colon-separated list of probe names. Note though that any delimiter, not just a colon may be employed. The probe preferably specifies a set of required dependencies and a list of optional dependencies. If the dependencies in the optional list are not available, then the probe manager assumes that those probes were run successfully. The required dependency list and the optional dependency list are separated by the ‘#’ character (again, any convenient delimiting character may be employed). For example, such a list may preferably take the following form:
         Product1.probeA:product1.probeB:product2.probeF#product2.probeG       

     For probes developed internally (that is, by the original manufacturer of the data processing system) the probes, probe utilities (if any; see below), probe configuration (if any; also, see below) and the message files are preferably installed under the standard top-level probe directory (named “/opt/diagnostics” in the pSeries of data processing systems manufactured and sold by International Business Machines Corp., the assignee of the present invention). 
     For probes developed by the user, the suggestion is to place the probes, utilities and the configuration in a directory that is different from the standard directory and using the following mechanisms to identify them to the probe manager and to the probes. The directory containing the user developed probes is specified by using the -d flag when invoking the probe manager. The directory containing user developed probe utilities is specified by using the USER_PROBE_UTILDIR environment variable. The user can also change the standard utilities directory by setting the STD_PROBE_UTILDIR environment variable, but in this case all the standard utilities would have to be copied to this new directory. The directory which contains configurations information for user developed probes is specified by using the USER_PROBE_CONFIGDIR environment variable. To change the configuration files for standard probes (those shipped as part of the diagnostic probes package), the user must copy all the standard configurations to another directory and modify the configuration files for specific probes to reflect the component configuration and then set the STD_PROBE_CONFIGDIR environment variable to point to this directory. It should be remembered that when changing the standard configuration directory, the configuration information for all the probes should be copied to the new directory. 
     Support for Writing Probes 
     A perl script based probe template is provided as part of the probe package in order to make it easy to develop probes in per. The probe template is preferably placed in the directory labeled “/opt/diagnostics/templates.” The template shows how to use the probe_support utility to handle tasks that are common to all probes, including the following tasks:
         parsing command-line arguments;   printing messages in the correct format;   filtering out messages based on command-line arguments; and   returning correct status codes.
 
The user developed probes may be placed in any directory and can express dependencies on the probes in the standard probes directory (/opt/diagnostics/probes).
       

     Probe Utilities 
     In order to complete its diagnostic work, a probe may need support scripts or some other executable(s). A set of standard utilities is shipped as part of the probe package and is, by default, located in the “/opt/diagnostics/utilities” directory. If desired, the user can change this by setting the STD_PROBE_UTILDIR environment variable. 
     A probe&#39;s authors may provide, along with the probe, a collection of utilities which are installed on the system. The utilities are preferably provided in a directory that is common to all probes and contains utilities that are useful to a plurality of probes. The location of this directory is preferably “/opt/diagnostics/utilitites” and can be changed by setting the environment variable STD_PROBE_UTILDIR. 
     Utilities developed by the users are preferably placed in a directory that is different from the standard utilities directory and this information is passed to user developed probes by setting the USER_PROBE_UTILDIR environment variable. 
     The following table provides a list of utilities which are may be typically provided by a system manufacturer. These are general utilities which are typically desirable for use in conjunction with certain probes and are further provided to ease development. All these utilities are preferably provided as perl scripts. All of the following utilities, unless otherwise noted, return exit status 0 on success, 1 on failure, and 127 when an unexpected error occurs. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Probe Utilities 
               
             
          
           
               
                 Utility 
                   
                   
               
               
                 Name 
                 Synopsis 
                 Description 
               
               
                   
               
               
                 fileperms 
                 fileperms filename 
                 Checks whether the 
               
               
                   
                 permission 
                 permissions on a specific 
               
               
                   
                   
                 file match the specified 
               
               
                   
                   
                 permission. The permission 
               
               
                   
                   
                 argument is an octal number 
               
               
                   
                   
                 representing the file 
               
               
                   
                   
                 permission. 
               
               
                 freespace 
                 freespace directory 
                 Determines the file system 
               
               
                   
                   
                 on which directory is 
               
               
                   
                   
                 located and then prints the 
               
               
                   
                   
                 free space on that 
               
               
                   
                   
                 filesystem. An absolute 
               
               
                   
                   
                 path name is to be 
               
               
                   
                   
                 provided for directory, 
               
               
                   
                   
                 not a relative one. 
               
               
                 gid2group 
                 gid2group gid 
                 Prints the group name 
               
               
                   
                   
                 associated with gid. An 
               
               
                   
                   
                 error occurs if gid is 
               
               
                   
                   
                 not found in /etc/group. 
               
               
                 group2gid 
                 group2gid groupname 
                 Prints the gid associated 
               
               
                   
                   
                 with groupname. An error 
               
               
                   
                   
                 occurs if groupname is 
               
               
                   
                   
                 not found in /etc/group. 
               
               
                 groupexist 
                 groupexist [gid|groupname] 
                 Checks whether the group 
               
               
                   
                   
                 specified by either gid 
               
               
                   
                   
                 or groupname exists 
               
               
                   
                   
                 in /etc/group. A success 
               
               
                   
                   
                 exit status indicates 
               
               
                   
                   
                 the group was found. 
               
               
                 portavail 
                 portavail [t|u] 
                 Checks whether the specified 
               
               
                   
                 portnumber|portname 
                 port is available. The utility 
               
               
                   
                   
                 examines TCP ports when -t 
               
               
                   
                   
                 is specified and UDP ports 
               
               
                   
                   
                 when -u is specified. The port 
               
               
                   
                   
                 parameter can be a port 
               
               
                   
                   
                 number or a service name 
               
               
                   
                   
                 listed in /etc/services. 
               
               
                   
                   
                 If service names is used and 
               
               
                   
                   
                 cannot be located, the script 
               
               
                   
                   
                 returns exit status 127. 
               
               
                 uid2user 
                 uid2user uid 
                 Prints the user name 
               
               
                   
                   
                 associated with uid. An 
               
               
                   
                   
                 error occurs if uid is not 
               
               
                   
                   
                 found in /etc/passwd. 
               
               
                 user2uid 
                 user2uid username 
                 Prints the uid associated 
               
               
                   
                   
                 with username. An error 
               
               
                   
                   
                 occurs if username is not 
               
               
                   
                   
                 found in /etc/passwd. 
               
               
                 userexist 
                 userexist [uid] [username] 
                 Checks whether the user 
               
               
                   
                   
                 specified by either uid 
               
               
                   
                   
                 or username exists 
               
               
                   
                   
                 in /etc/passwd. A success 
               
               
                   
                   
                 exit status indicates the 
               
               
                   
                   
                 user was found. 
               
               
                 whatgroup 
                 whatgroup filename 
                 Prints the group who owns 
               
               
                   
                   
                 filename. 
               
               
                 whoowns 
                 whoowns filename 
                 Prints the user who owns 
               
               
                   
                   
                 filename. 
               
               
                 osinfo 
                 osinfo 
                 Prints the operating system 
               
               
                   
                   
                 information. The output 
               
               
                   
                   
                 format is Operating System 
               
               
                   
                   
                 name: Distributor: Version 
               
               
                 csmnodetype 
                 csmnodetype 
                 Determines the type of CSM 
               
               
                   
                   
                 node. The output is one of 
               
               
                   
                   
                 ManagementServer, 
               
               
                   
                   
                 ManagedNode or Unknown 
               
               
                   
               
             
          
         
       
     
     Probe Configuration 
     A probe may require access to some configuration parameters (for example, location of a subsystem&#39;s configuration). For example, if an application depends on another application that runs on another remote machine and the application gets the hostname of the remote machine from a file located in a specific directory, this file can be called as the configuration file for the application. Consequently, there is provided a predefined directory where all probes may find a configuration file. The location of this directory is specified via the STD_PROBE_CONFIGDIR environment variable. The name of the file is determined by the probe. The probe, however, does not write to this file. The information in the file represents system-specific options that a probe uses while examining the system. A probe&#39;s operation should not depend on the configuration file. If the probe cannot find the configuration file, the probe falls back upon reasonable defaults and outputs an attention message with the default values that are used by the probe. If reasonable defaults cannot be determined, then the probe terminates with a return code of 127 indicating that an internal error occurred. 
     The STD_PROBE_CONFIGDIR environment variable determines the directory where probe configurations are stored. The directory name should not be relative (that is, it should begin with a ‘/’). If the variable is unset, the configuration directory is “/opt/diagnostics/config.” 
     For user developed probes the USER_PROBE_CONFIGDIR environment variable is used to specify the directory where the configuration files for those probes reside. 
     A set of diagnostic probes providing basic diagnostic functionality is preferably provided by system manufacturers when a system is shipped or when its software is upgraded. A typical set of these basic diagnostic probes are set forth in Table II below: 
                                   TABLE II                   Available Base Probes            Probe Name   Dependencies   Description               fs.mounts   None   Checks to make sure that all filesystems specified in /etc/fstab as               automount (i.e.. the noauto flag is not given) are actually               mounted. Also ensures that the files are indeed read-only if that               is specified or read-write if nothing is specified.       network   network.enabled,   This is a dummy probe that expresses dependencies on all other           network.hostname,   network probes. This probe with all of its dependencies verifies           network.ifaces,   proper operation of network devices and verifies IP settings. It           network.ip_defrag,   checks route configuration and also attempts to ping the local           network.ip_forward,   machine.           network.ping,           network.routes       network.enabled   None   This probe checks to see if NETWORKING = yes in               /etc/sysconfig/network. It returns an error if it is “no” or if               /etc/sysconfig/network does not exist.       network.hostname   None   This probe checks to see if the hostname in               /etc/sysconfig/network is consistent with the hostname of the               system.       network.ifaces   network.enabled   This probe checks that the interfaces specified in               /etc/sysconfig/network-scripts/ifcfg -* have the specified               parameters (IP address, netmask, and broadcast address). It also               ensures the interfaces are up and running. For dynamically               configured interfaces this probe only ensures the device exists               and the interface is up.       network.ip_defrag   None   This probe checks to see if the enabled status IP auto               defragmentation is consistent with /etc/sysconfig/network. This               probe relies on the /proc filesystem. It also relies on the ability to               configure IPv4 parameters at runtime.       network.ip_forward   None   This probe checks to see if the enabled status IP forwarding is               consistent with /etc/sysconfig/network. This probe relies on the               /proc filesystem. It also relies on the ability to configure IPv4               parameters at runtime.       network.ping   network.enabled,   This probe tries to ping each interface of the local machine           network.ifaces,   ensuring that it is properly responding. It sends 10 ICMP echo           network.routes   packets to each interface and counts the number of replies. No               replies implies there is an error. If less than 10 replies are               received, a warning is displayed. There is a timeout period of 10               seconds, which should be sufficient.       network.routes   network.enabled,   This probe ensures that the routes that should be created for each           network.ifaces,   interface and the default routes are in the kernel route table. This               probe does not check for the routes specified in               /etc/sysconfig/static-routes. It prints a warning for any interface               that does not specify its IP address in its configuration file,               which produces an attention message for every interface that is               dynamically configured.               Attention: This probe incorrectly gives error messages if               host/network names are used in the configuration files               rather than addresses in dotted quad notation.                    
Note: In the table above the term “dotted quad configuration” refers to an IP (Internet Protocol) Address represented as in the format ww.xx.yy.zz (such as, 161.53.4.28).
 
     Repairing Software 
     In addition to diagnosing problems in software components, probes can also sometimes suggest fixes for the problem found. Since each probe is a “domain expert” with respect to the component it is analyzing, it is reasonable to expect that in some cases the probe “knows” exactly what caused the problem and how to resolve it. To enable this, an additional message level (see Probe Output section) is defined called “Fix”. For this message level, the message text is actually a command string that can be run to address the problem found. This command is normally run by the probe manager or a higher level application (for example, a probe GUI) after displaying the problem message to the user and asking the user whether or not the fix should be executed. For cases in which the solution is less exact, another message level called “Suggestion” is defined. This is output by the probe to give the user instructions on how to solve the problem. 
     While the invention has been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and changes therein may be effected by those skilled in the art. Accordingly, it is intended by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.