Abstract:
Disclosed are a method of and system for defining user account validity in a cluster of computer systems. The method comprises the steps of providing a centralized management system for said cluster; and using said centralized management system to maintain a record indicating, for each user of the cluster, whether the user is valid on each of the computer systems in the cluster. Preferably, the step of using said centralized management system includes the step of using said centralized management system to create a user account validity definition, and to identify in said definition which ones of the users are valid on which ones of the computer systems.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the invention  
         [0002]     This invention generally relates to computer clusters, and more specifically, to user account validity definitions in computer clusters.  
         [0003]     2. Background Art  
         [0004]     A computer cluster is a collection of one or more computer systems that are linked together to cooperatively perform computer-implemented tasks, such as providing client computers with access to a set of services and resources. Typically, computer clusters are fault tolerant and are provided with load balancing algorithms.  
         [0005]     Each computer of a computer cluster may be a multiprocessor system itself. For example, a cluster of four computers, each with four CPUs, would provide a total of 16 CPUs processing simultaneously. If one of the computers fails, one or more additional computers are still available and may actually take over the functions of the failed computer. In addition, load-balancing mechanisms in the computer cluster are able to distribute the workload over the multiple computer systems, thereby reducing the burden on each of the computer systems.  
         [0006]     Another important advantage of a computer cluster is its scalability, as it has the flexibility to enable additional cluster elements to be added to the cluster or incorporated within existing cluster elements. Further, a computer cluster provides the flexibility to enable existing cluster elements, or components within a cluster element, to be upgraded or modified.  
         [0007]     User management systems for a cluster of computer systems (such as UNIX authentication via LDAP or NIS) provide a centralized facility to create, delete and modify user accounts that are valid for all systems that are part of the cluster. A user account that is valid on a system provides the ability for login access, and file and process creation, deletion, and ownership. In some instances, while central user management is essential, it may not be desirable that a user account be valid on all systems in a cluster. A mechanism presently exists to restrict the systems where a user may login. For example, some operating systems include attributes hostsallowedlogin and hostsdeniedlogin, which define a set of computer systems where a user account may or may not gain login access. Also, the login facility ssh is configurable to define which user accounts are valid for login access. Both methods, however, do not prevent the user account from being used to create, delete, and own files or processes. To prevent a user from performing such activities, the user simply must not be defined on the system. Presently, in centralized user management systems, such “selective validity” is not available or configurable: Either the user is valid on all nodes in the cluster or it is not, irrespective of whether or not a user may login to one or more nodes.  
       SUMMARY OF THE INVENTION  
       [0008]     An object of this invention is to improve computer clusters.  
         [0009]     Another object of the present invention is to provide a new user account validity definition in clustered computer systems.  
         [0010]     A further object of the invention is to provide an administrator of a computer cluster with selective validity on the nodes of the cluster.  
         [0011]     An object of the invention is to create a user account in a computer cluster and to use that user account name to determine where the user exists or does not exist in the cluster.  
         [0012]     These and other objectives of the invention are achieved with a method of and system for defining user account validity in a cluster of computer systems. The method comprises the steps of providing a centralized management system for said cluster; and using said centralized management system to maintain a record indicating, for each user of the cluster, whether the user is valid on each of the computer systems in the cluster. Preferably, the step of using said centralized management system includes the step of using said centralized management system to create a user account validity definition, and to identify in said definition which ones of the users are valid on which ones of the computer systems.  
         [0013]     Also, preferably, each of the computer systems of the cluster is provided with a user authentication module; and when one of the users requests authentication on one of the computer systems, the user authentication module of that one of the computer systems is used to determine whether that one of the users is valid on that one of the computer systems. For example, the centralized management system may be used to maintain a list on the centralized management system identifying which of the users have access to which of the computer systems; and when one of the users requests authentication on one of the computer systems, the user authentication module the one of the computer systems is used to ask the centralized management system whether the one of the users is valid on the one of the computer systems. Alternatively, each of the computer systems may be provided with a cache of user account values; and when one of the users requests authentication on one of the computer systems, the user authentication module of that one of the computer systems is used to access the cache of user account values of that one of the computer systems to determine if the requesting user is valid on the one of the computer systems.  
         [0014]     With the preferred embodiment of the invention, described in detail below, user authentication modules on an individual system in the cluster check an attribute that defines a user account&#39;s “validity” on the local system for each request processed by the module. If the attribute defines the user as “valid” on the system, then the request proceeds normally. If the attribute defines the user as “not valid”, then the module would return an error status that “the user does not exist” on the local system to the requestor.  
         [0015]     With this mechanism in place, a cluster administrator managing a cluster of 1000 nodes, for example, has the ability to centrally define user accounts, but can isolate the validity of a single account to 400 of those nodes where the user is permitted to manage processes and files. The account would not be valid on the other 600 nodes in the cluster where the user is not permitted to manage processes and files. This is more convenient and efficient than having to define the user manually on 400 nodes.  
         [0016]     An important advantage of this technique is that an administrator can create a user account in a cluster and decide where the user exists or does not exist in the cluster. With the mechanism of this invention in place—and in contrast to the use of the above-mentioned hostdeniedlogin attribute—the computer operating system will not allow the creation of files, processes, or other system resources (su for example) for or associated with a user id. For all intents and purposes, the user id does not exist on that host. As an added benefit, if the user&#39;s access requirements grow to an additional 200 nodes, for example, then the validity definition only needs to be changed, instead of creating the user account on the additional 200 nodes. The mechanism can also be used to temporarily suspend the validity of a user account in a cluster while preserving the user&#39;s definition in the central user management system.  
         [0017]     Further benefits and advantages of the invention will become apparent from a consideration of the following detailed description, given with reference to the accompanying drawings, which specify and show preferred embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  illustrates a computer cluster.  
         [0019]      FIG. 2  is an exemplary diagram showing a distributed data processing system that may be used in the present invention.  
         [0020]      FIG. 3  shows attributes that specify where a user account is valid and not valid in a computer cluster.  
         [0021]      FIG. 4  illustrates an example of node groups that may be used in the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]      FIG. 1  illustrates a computer cluster  100  comprising a plurality of computer systems or nodes  102 ,  104 ,  106 ,  110 , and this cluster is connected to clients  112  and  114  via network  116 .  FIG. 1  also shows a cluster administrator  120  and a path manager  122 .  
         [0023]     The computing systems  102 ,  104 ,  106 ,  110  constitute a cluster in which a first computing system may be used as a backup of a second computing system should the second computing system fail. The functions and resources of the failed second computing system may be taken over by the first computing system in a manner generally known in the art.  
         [0024]     The computing systems  102 ,  104 ,  106 ,  110  may be any type of computing system that may be arranged in a cluster with other computing systems. For example, the computing systems  102 ,  104 ,  106 ,  110  may be server computers, client computers, and the like. The computing systems  102 ,  104 ,  106 ,  110  may be single processor systems or multiprocessor systems. In short, any type of computing system that may be used in a cluster with other computing systems is intended to be within the spirit and scope of the present invention.  
         [0025]     The computing systems  102 ,  104 ,  106 ,  110  are coupled to one another via communication links  130 ,  132 ,  134 ,  136 ,  140 ,  142 . The communication links  130 ,  132 ,  134 ,  136 ,  140 ,  142  may be any type of communication links that provide for the transmission of data between the computing systems  102 ,  104 ,  106 ,  110 . For example, the communication links may be wired, wireless, fiber optic links, satellite links, infrared links, data buses, a local area network (LAN), wide area network (WAN), the Internet, or the like. Any type of communication link may be used without departing from the spirit and scope of the present invention.  
         [0026]     Cluster administrator  120  is provided to manage computer cluster  100  and, for instance, provides a centralized facility to create, delete and modify user accounts. Path manager  122  is provided to route data between the computer systems of cluster  100 . In a preferred embodiment, path manager  122  operates in a distributed fashion through a local component residing within each node in cluster  100 . Path manager  122  knows about the interconnection topology of cluster  100  and monitors the status of communication pathways through the cluster. Path manager  122  also provides an interface registry through which other components interested in the status of the interconnect can register. This provides a mechanism for the path manager to make callbacks to the interested components when the status of a path changes, if a new path comes up, or if a path is removed.  
         [0027]     Clients  112  and  114  can include any node on network  116  having a computational capability and including a mechanism for communicating across network  116 . In one embodiment of the present invention, clients  112  and  114  communicate with cluster  100  by sending packets to the cluster in order to request services from the cluster.  
         [0028]     Network  116  can include any type of wire or wireless communication channel capable of coupling together computing nodes. This includes, but is not limited to, a local area network, a wide area network, or a combination of networks. For example, network may be or include the Internet.  
         [0029]     Referring to  FIG. 2 , a block diagram of a data processing system that may be implemented as a computing system in a clustered system, such as clustered system  100  in  FIG. 1 , is depicted. Data processing system  200  may be a symmetric multiprocessor (SMP) system including a plurality of processors  202  and  204  connected to system bus  206 . Alternatively, a single processor system may be employed. Also connected to system bus  206  is memory controller/cache  208 , which provides an interface to local memory  209 . I/O bus bridge  210  is connected to system bus  206  and provides an interface to I/O bus  212 . Memory controller/cache  208  and I/O bus bridge  210  may be integrated as depicted.  
         [0030]     Peripheral component interconnect (PCI) bus bridge  214  connected to I/O bus  212  provides an interface to PCI local bus  216 . A number of modems may be connected to PCI local bus  216 . Typical PCI bus implementations will support four PCI expansion slots or add-in connectors. Communications links to network computers  102 ,  104 ,  106 ,  110  in  FIG. 1  may be provided through modem  218  and network adapter  220  connected to PCI local bus  216  through add-in boards.  
         [0031]     Additional PCI bus bridges  222  and  224  provide interfaces for additional PCI local buses  226  and  228 , from which additional modems or network adapters may be supported. In this manner, data processing system  200  allows connections to multiple network computers. A memory-mapped graphics adapter  230  and hard disk  232  may also be connected to I/O bus  212  as depicted, either directly or indirectly.  
         [0032]     Those of ordinary skill in the art will appreciate that the hardware depicted in  FIG. 2  may vary. For example, other peripheral devices, such as optical disk drives and the like, also may be used in addition to or in place of the hardware depicted. The depicted example is not meant to imply architectural limitations with respect to the present invention.  
         [0033]     The data processing system depicted in  FIG. 2  may be, for example, an IBM e-Server pSeries system, a product of International Business Machines Corporation in Armonk, N.Y., running the Advanced Interactive Executive (AIX) operating system or LINUX operating system.  
         [0034]     As mentioned above, presently, in centralized user management computer clusters, selective validity of users on individual computer systems is not available or configurable: Either the user is valid on all nodes or it is not, irrespective of whether or not a user may login to one or more nodes. The present invention provides such selective validity. Generally, in accordance with this invention, user authentication modules on an individual system in the cluster check an attribute that defines a user account&#39;s “validity” on the local system for each request processed by the module. If the attribute defines the user as “valid” on the system, then the request proceeds normally. If the attribute defines the user as “not valid,” then the module would return an error status that “the user does not exist” on the local system to the requester.  
         [0035]     With this mechanism in place, a cluster administrator managing a cluster of 1000 nodes, for example, has the ability to centrally define user accounts, but can isolate the validity of a single account to 400 of those nodes where the user is permitted to manage processes and files. The account would not be valid on the other 600 nodes in the cluster where the user is not permitted to manage processes and files. This is more convenient and efficient than having to define the user manually on 400 nodes.  
         [0036]     An important advantage of this technique is that an administrator can create a user account in a cluster and decide where the user exists or does not exist in the cluster. As an added benefit, if the user&#39;s access requirements grow to an additional 200 nodes, for example, then the validity definition only needs to be changed, instead of creating the user account on the additional 200 nodes. The mechanism can also be used to temporarily suspend the validity of a user account in a cluster while preserving the user&#39;s definition in the central user management system.  
         [0037]     More specifically, in a preferred embodiment, the invention works by including two attributes, validforhosts and invalidforhosts, for example, that define the hosts in the cluster where the user account is valid and invalid. The attribute is preferably included as part of the user account definition in the central user management system (e.g., LDAP or NIS). The authentication module on an individual system in the cluster would, upon request for authentication or authorization for a specific user, check for the validity of that user in the system by requesting the information from the central user management system. The request would be processed at the central server, or locally against a cache of user account values (if configured). Alternatively, a file, /etc/security/validusers, for example, would include attribute definitions for validforhosts and invalidforhosts. This file would then be distributed to each node using a central distribution system such as IBM Cluster Systems Management (CSM) Configuration File Management (CFM). In this configuration, the authentication module on the individual system would instead verify the validity of a user account by reading the local file for each user authentication or authorization request. If a match is not found in the validusers file or its cache, then the system would request the information from the central user management system.  
         [0038]     The attributes validforhosts and invalidforhosts specify a list of the hosts where a user account is valid and not valid. For example, consider the user account jsmith shown in  FIG. 3 . In this case, if any authentication or authorization requests were made for jsmith on node 1 , node 2 , or node 3 , the user account would be considered valid by the user authentication module on those nodes. If any user authentication or authorization requests were made for jsmith on node 4  and node 5 , the user account would be considered as invalid or “non-existent” on those nodes. This means that jsmith cannot login or as another user create processes or files that are owned by jsmith. Although defined in the user management system, the Operating system would treat jsmith as if the account did not exist.  
         [0039]     The two valid attributes work together to determine where a user is valid. Both attributes are provided for flexibility when specifying a user&#39;s validity. Empty attributes indicate that a user is valid everywhere in the cluster. Wildcards can be used to specify validity: invalidhosts=* means that a user is invalid everywhere in the cluster. If a host H 1  is included in both the validforhosts and invalidforhosts, the invalid definition has precedence over the valid definition, and the user account is invalid on host H 1 .  
         [0040]     With the user of the invalidforhosts as described above—and in contrast to the use of the hostdeniedlogin attribute mentioned above—the computer operating system will not allow the creation of files, processes, or other system resources (su for example) for or associated with a user id. For all intents and purposes, the user id does not exist on that host.  
         [0041]     To improve the specification of valid hosts, integration of the user management system with a cluster systems management environment, such as IBM CSM can be an option. CSM provides the notion of user definable node groups. A node group, for example as shown in  FIG. 4 , is a container/reference to addressable nodes within the cluster. Instead of specifying multiple hosts in the validforhosts or invalidforhosts list, a single node group can be used, for instance as shown in  FIG. 4 .  
         [0042]     It should be understood that the present invention can be embodied in a computer program product, which comprises all the respective features enabling the implementation of the methods described herein, and which—when loaded in a computer system—is able to carry out these methods. Computer program, software program, program, or software, in the present context mean any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: (a) conversion to another language, code or notation; and/or (b) reproduction in a different -material form.  
         [0043]     While it is apparent that the invention herein disclosed is well calculated to fulfill the objects stated above, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art and it is intended that the appended claims cover all such modifications and embodiments as fall within the true spirit and scope of the present invention.