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HELIOS EtherShare UB User manual |
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The following section contains miscellaneous technical information about EtherShare which is primarily of interest to experienced system administrators only.
In order to be able to communicate using the AppleTalk protocols, EtherShare needs support from the operating system. Commonly, UNIX suppliers deliver the TCP/IP networking protocols together with their standard operating system release, but no AppleTalk networking protocols. EtherShare thus contains drivers that implement the AppleTalk protocol with Ethernet. On some machines, EtherShare also supports other network connections like Token Ring. All files that relate to the kernel side of the EtherShare system reside in the directory "HELIOSDIR/etc/kernel". The following is a detailed description of what is changed in the operating system by the EtherShare installation. This is probably of interest to advanced UNIX users only, since the EtherShare configuration shell scripts hide most of the details necessary to get the AppleTalk drivers running.
The kernel modules come in two flavors, depending on host operating system architecture. System V.4 based systems use a stream-based architecture where each AppleTalk communication endpoint is represented as a file descriptor opened through the streams multiplexor "/dev/ddp". Berkeley-based systems use file descriptors opened through the socket mechanism.
Solaris, SGI IRIX, HP-UX 11, and IBM RS/6000 systems support a concept of loading drivers, which can be loaded into the operating system during runtime. In such cases, it is not necessary to re-link the UNIX kernel with new modules. The "start-helios" shell script takes care of loading the driver when starting AppleTalk, if the driver is not already loaded.
EtherShare uses two kernel modules on Solaris systems, "aarp" contains the "AppleTalk Address Resolution Protocol" streams module and "ddp" the "Datagram Delivery Protocol" streams multiplexor. "aarp" is located in "/kernel/strmod" and "ddp" in "/kernel/drv". During installation the files are copied from "HELIOSDIR/etc/kernel" to the "/kernel" directory. In addition, the installation script adds a line to the "/etc/minor_perm" and "/etc/devlink.tab" and files to get the proper link from "/devices/pseudo/clone:ddp" entry to "/dev/ddp" using the proper permissions. The drivers are loaded and unloaded by Solaris automatically, no loading or unloading should be necessary.
A long list of all loaded modules can be produced by using the "modinfo" command. The "modunload" command can be used to unload the drivers, but only if they are unused.
On IBM RS/6000 systems, only one driver is loaded by the "start-helios" script ("HELIOSDIR/etc/kernel/atalk"). This driver is dependent upon the AIX version. The installation procedure makes a link from the corresponding and appropriate file to "/usr/lib/drivers".
In addition, entries are added to the ODM database to allow the loading of the driver through the "mkdev" command. The logical name for the kernel module is "atalk0". Use the following command to load the module:
Note: Under AIX, the unloading of network protocols is not supported.
On SGI IRIX systems, the loadable drivers reside in "HELIOSDIR/etc/kernel" and are automatically loaded by "start-helios" with the ml command. A list of all loaded drivers can be displayed using ml list. With ml unld and the corresponding ID number (which can be obtained from the drivers list) the module can be unloaded again.
The drivers "aarp" and "ddp" are copied into the system directory of a HP-UX 11 operating system by the "kminstall" command. To automatically load the modules in the kernel use "kmupdate".
Many of the functions of EtherShare are aided by the high performance of the UNIX operating system, and EtherShare is closely integrated with a number of the more common system programs and facilities in UNIX.
For example, EtherShare often uses the host program "syslogd". This program is responsible for passing information within the host system itself, and is used by EtherShare mainly as a medium of transport.
"syslogd", which runs continuously in the background within UNIX, has the task of processing status and error messages from other active programs, and sending them to a specific output device or file in accordance with its configuration. All of the EtherShare modules use the services of "syslogd" to output system error messages and warnings.
By changing the configuration file "/etc/syslog.conf" on the server, the administrator is able to exactly control the flow of messages. For example, messages can be automatically passed on to users logged-on to the system (or entire groups), or simply stored in files or output to the system console.
With some operating systems, EtherShare (as many other UNIX programs) will not log any error messages or warnings unless "syslogd" has been appropriately configured.
Important: For the following commands it is required to use the HELIOS "dt utilities". These utilities mimic the functionality of the UNIX commands "mkdir", "rmdir", "chmod", "chown", "chgrp", etc., while maintaining the integrity of the desktop database. The "dt utilities" are described in the Base manual.
The UNIX program "mkdir" can be used to create new subdirectories in the UNIX file system. "mkdir" can also be used by the administrator to create new folders for the Macintosh. Please refer, however, to the notes contained in 6.3 "Directory and file formats". Folders are best created or deleted by using the Finder on a Macintosh workstation. "rmdir" (remove directory) can be used to remove directories/folders when they are no longer needed.
The UNIX system program "chmod" (change mode) can be used to change user privileges for files and directories in the UNIX file system. You can also use "chmod" to change access privileges for HFS (Hierarchical File System) volumes created for Macintosh computers on the EtherShare file server, although you should normally use the Macintosh program Get Info (in the File menu) for this purpose. Please refer to 6.3 "Directory and file formats" and 6.6 "Access privileges".
Important: You should never change the privileges of files in the EtherShare program directories, or in spool directories used by the HELIOS print server.
The UNIX programs "chown" and "chgrp" can be used to change the owner (creator) or group of a file or directory, although you should normally use the Macintosh program Get Info (in the File menu) for this purpose. Only the system administrator can change the owner of a file or change the file's group to one in which the owner is not a member.
The UNIX program "cron" (cronos <Greek>= time), which runs continuously within UNIX, can be configured to start and stop specified programs at predetermined times. An appropriate entry in the cron configuration table (crontab) can be used to start and stop a particular server at a specified time of day. "cron" can also be used to automate data backup procedures.
"ufsdump" is a data archiving program available on BSD UNIX systems. It is the recommended program for making backup (security) copies of network volumes to a tape streamer or other removable storage media attached to the UNIX host. You can read in the archive again with "restore". See also "Data backup" in the Base manual.
| © 2005 HELIOS Software GmbH |
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