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As you can see in the SunOS 4.1.x configuration, an extensive list of daemons are started to service users and provide system-level services. Notice that these daemons are started from only two startup files. This setup makes the maintenance of the SunOS system easier because the startup routines aren’t scattered all over the place. Obviously, this is an important benefit when you need to make changes to the startup process, such as add new daemons, modify the operation of existing ones, or remove unneeded daemons.
It is important to consider that the startup procedures of the various Unix flavors often are very different depending upon the heritage. SunOS 4.1.x, for example, is derived from the Berkeley Software Distribution (BSD) code and as such bears little or no resemblence to the startup procedure seen in Solaris 2.x, which is based upon the Unix System Laboriatories Unix System V Release 4.
The same is true when comparing Unix System V Release 3.2 and Release 4. These differences are important to note, because they make it easier to hide inconspicuous programs for later action.
Table 2.2 lists daemons that are used to start and operate the HP-UX operating system on a Hewlett-Packard HP9000 Series 700 workstation.
| File Name | Daemon | Description |
|---|---|---|
| /etc/rc | lpsched | Printer daemon |
| cron | Executes commands at specified dates and times | |
| vtdaemon | Responds to vt requests | |
| envd | System physical environment daemon | |
| rbootd | Remote boot server | |
| syslogd | Logs system messages | |
| /etc/netlinkrc | nettl | Controls network tracing and logging |
| inetd | Internet services daemon | |
| /etc/audiorc | Aserver | Audio server |
| /etc/netbsdsrc | gated | Network routing daemon |
| named | Internet domain name server | |
| rwhod | System status server | |
| sendmail | Sends mail over the Internet | |
| /etc/netnfsrc | portmap | TCP/IP port to RPC program number mapper |
| ypserv | NIS server | |
| ypbind | NIS domain binding agent | |
| rpc.mountd | NFS mount request server | |
| nfsd | Client file system requests | |
| biod | Asynchronous block I/O daemons | |
| pcnfsd | (PC)NFS authentication and print request server | |
| rpc.lockd | Network lock daemon | |
| rpc.statd | Network status monitor | |
| /etc/netnmrc | snmpd | Daemon that responds to SNMP requests |
The HP-UX startup sequence makes use of a large number of files, each of which are tightly linked to a given subsystem. For example, the file netlinkrc is used to start the network processes. With this type of startup file layout, it is much harder to locate the daemons and to modify the system startup procedure.
Regardless of the Unix implementation being considered, the use of the /etc/rc file to start the system is common. Consider the list of files required to start the daemons on an SCO OpenServer 5.0 system. Table 2.3 lists the daemons and their start up file locations.
| File Name | Daemon | Description |
|---|---|---|
| /etc/rc2.d//01MOUNTFSYS | auditd | Reads audit collection files generated by the audit subsystem and compact the records |
| /etc/rc2.d/P75cron | cron | Executes commands at specified dates and times |
| /etc/rc2.d/P86mmdf | deliver | Handles the management of all mail delivery |
| /etc/rc2.d/S80lp | lpsched | Printer daemon |
| /etc/rc2.d/S84rpcinit | portmap | TCP/IP port to RPC program number mapper |
| rwalld | Network rwall server | |
| rusersd | Network user name server | |
| rexd | RPC-based remote execution server | |
| /etc/rc2.d/S85nis | ypserv | NIS server and binder processes |
| ypbind | NIS server and binder processes | |
| /etc/rc2.d/S85tcp | maskreply | Sends gratuitous ICMP mask reply |
| syslogd | Logs system messages | |
| inetd | Internet services daemon | |
| snmpd | Daemon that responds to SNMP requests | |
| named | Internet domain name server | |
| routed | Network routing daemon | |
| irdd | Internet Router Discovery daemon | |
| gated | Network routing daemon | |
| rarpd | TCP/IP Reverse Address Resolution Protocol server | |
| timed | Time server daemon | |
| rwhod | System status server | |
| lpd | Printer daemon | |
| /etc/rc2.d/S89nfs | nfsd | Client file system requests |
| mountd | NFS mount request server | |
| pcnfsd | (PC)NFS authentication and print Request server | |
| biod | Asynchronous block I/O daemons | |
| automount | Automatically mounts NFS file systems | |
| statd | Network status monitor | |
| lockd | Network lock daemon | |
SCO Unix products use a file system structure that is grouped by the desired run level. Run levels, their meanings, and how to switch between them are discussed in the section, “Unix Run Levels.”
Like the HP-UX implementation, a number of SCO Unix startup scripts are used to start daemons. Each script essentially is dedicated to starting the daemons for a specific function group. This is not necessarily bad design, but it requires a detailed level of understanding of the underlying system structure.
The following sections examine what each of these daemons offers to the system and to the users of that system.
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