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Section: C Library Functions (3)
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cfg_subsys_reconfig - Reconfigure attribute values for a subsystem  


Configuration Management Library (libcfg.a)  


#include <cfg.h> cfg_status_t cfg_subsys_reconfig(
        cfg_handle_t *handle,
        caddr_t subsys,
        cfg_attr_t *attributes,
        int nattributes);  


Structure identifying the means of communication between your application and the configuration management server. For local requests, pass NULL in this parameter. For remote requests, pass the value returned from the cfg_connect() routine. Specifies the name of the subsystem for which you are modifying attribute values. On input, contains a list of attributes whose value you want to modify. For each attribute, the list includes the attribute name, data type, and the new value.

On return, contains a status for each attribute. The status indicates whether the system was able to make the modification and, if not, what problem caused the error. The number of attributes whose values you are changing.


Use the cfg_subsys_reconfig() routine to modify attribute values for a subsystem. The modifications made by this routine take effect immediately because they are made to the in-memory copy of the subsystem. Neither the kernel nor the subsystem stores a copy of the modifications, so if the system is rebooted or the subsystem is unconfigured the modifications are lost. When the subsystem is once again configured into the kernel, the value of its attributes are retrieved from the /etc/sysconfigtab database and the subsystem code.

To make permanent changes to attribute values, store the new attribute values in the /etc/sysconfigtab database. See sysconfigtab(4) for information about that database.

When your application calls the cfg_subsys_reconfig() routine, it passes a list of attribute names and values. The application passes this information in an array of structures of type cfg_attr_t. For information about this structure, see libcfg(3). The following list describes the information that is passed to the system by your application: Attributes can be integer, string, or binary data. To specify the data type of your attribute you pass one of these attribute data types: CFG_ATTR_STRTYPE, CFG_ATTR_INTTYPE, CFG_ATTR_UNITTYPE, CFG_ATTR_LONGTYPE, CFG_ATTR_ULONGTYPE, CFG_ATTR_BINTYPE For attributes that are themselves a structure, your application must pass the index for the attribute whose value you want to modify. The attribute value specifies the new value for the attribute.

Be aware that the system updates attributes in the order in which you specify them in the attribute list. This order can be important when one attribute is validated based on another attribute's current setting. On return, the system supplies the status for each attribute. The status is returned in the attribute parameter, which is normally an array of structures of the type cfg_attr_t. For information about this structure, see libcfg(3). The following table describes the status values your application might receive from the cfg_subsys_reconfig() routine:

Status CodeMeaning

CFG_ATTR_SUCCESSSuccessful operation
CFG_ATTR_EEXISTSNo attribute by that name exists
CFG_ATTR_EOP Attribute does not support the reconfigure operation
CFG_ATTR_ESUBSYS Subsystem failure (code within the subsystem returned an error)
CFG_ATTR_EINDEX The index for an indexed attribute is out of range
CFG_ATTR_ELARGE The new attribute value or length is too large
CFG_ATTR_ESMALL The new attribute value or length is too small



The following example illustrates the use of the cfg_subsys_reconfig() routine: cfg_attr_t attributes[1]; cfg_status_t retval; cfg_handle_t handle; int i; int nattributes;

/*****************************************************/ /* Initialize attribute names for the request */

strcpy (attributes[0].name, "maxmounts"); attributes[0].type = CFG_ATTR_INTTYPE; attributes[0].attr.num.val = 30; nattributes = 1;

/***************************************************/ /* Call the cfg_subsys_reconfig() routine */

retval = cfg_subsys_reconfig(&handle, "lvm", attributes, nattributes);

if (retval != CFG_SUCCESS)
    print_error (retval);

else {

     for (i=0; i<1; i++) {
        if (attributes[i].status != CFG_ATTR_SUCCESS) {
            printf("%s:", attributes[i].name);
            switch (attributes[i].status){
             case CFG_ATTR_EEXISTS:
               printf("unknown attribute\n");
             case CFG_ATTR_EOP:
               printf("attribute does not allow this operation\n");
               break; . . .
               printf("unknown error\n");
    } }

In this example, the application attempts to modify the value of the maxmounts attribute. This attribute, which is part of the lvm subsystem is being set to the value 30.

On return the application checks the status of the request as a whole and of the attribute itself. If the request and attribute status both indicate success, the application continues. Otherwise, an error is displayed.  


Upon successful completion, cfg_subsys_reconfig() returns CFG_SUCCESS. Other return values indicate that an error has occurred. For information about handling return values from routines in the configuration management library, see libcfg(3).  


Commands: cfgmgr(8), sysconfig(8)

Routines: libcfg(3) delim off




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Time: 02:42:16 GMT, October 02, 2010