2.1 An SNMP agent for managing UNIX workstations

  In contrast to existing commercial solutions ([4], [8]) generally based on a bottom-up approach, we focused on covering typical tasks of Unix system administrators. This top-down analysis [2] revealed the need for supporting multiple issues: The creation and deletion of user accounts and groups, the management of user quotas for system resources like storage or printer usage, the mount/unmount of filesystems and functions for starting and stopping processes. It is easy to see that the capabilities of the agent are beyond the usual monitoring tasks by permitting the execution of actions on behalf of the systems. The transfer of management information is done through the SNMPv2 management protocol.

The analysis led to the development of a UNIX workstation MIB and to the implementation of a systems management agent running on different platforms (HP-UX, IBM AIX, Sun Solaris, SunOS). The structure of this MIB is depicted in figure 2; the MIB consists of 195 variables and 15 tables and represents, among others, the following components:

  

Figure 2: Structure of the UNIX workstation MIB (taken from [2])

• Memory (main memory, swap-space)
• Devices (CPUs, printers, storage disks and filesystems etc.)
• Processes (user processes, kernel processes)
• Users (passwords, groups, quota etc.)

In order to cope with the large heterogeneity of the four supported operating systems and to enable the adaption of the agent to new provider requirements, the agent has been implemented in a modular way: Every way of accessing a MIB variable is represented by a different procedure. This means that every MIB variable has been implemented in a separate module and has either one or two interfaces, depending on whether the variable is readonly or read- and writeable. The value of a readonly MIB variable like sysName is obtained through the get_sysName procedure; variables which can be read and written are accessed through their appropriate get and set procedures.