Unix Preparations on the Master PC

A number of simple Unix-level modifications of the master PC (e.g., NFS export of the CDROM drive) are needed before starting the Linux installation on the remaining hrothgar PCs.

Exporting hrothgar's CDROM Drive

Of the four PC's in the original hrothgar Beowulf system, only the Master PC has a CDROM drive. In order to use this drive via NFS for Linux installations on the remaining PCs, a few simple edits to files in /etc were needed.

Log into hrothgar (as root), change directory to /etc, then

  1. Modify the fstab file to make the CDROM drive usefully exportable. The modified /etc/fstab on hrothgar contained the lines:
    /dev/hda1 / ext2 defaults 1 1 /dev/hda5 /home ext2 defaults 1 2 /dev/hda6 swap swap defaults 0 0 /dev/fd0 /mnt/floppy ext2 noauto 0 0 /dev/cdrom /mnt/cdrom iso9660 noauto,ro,user,unhide 0 0
    (The user,unhide entries in the /dev/cdrom line are the key parts).

  2. Modify the exports file to include the CDROM. The exports file on hrothgar became:
    /mnt/cdrom 192.168.8.41(ro) /mnt/cdrom 192.168.8.42(ro) /mnt/cdrom 192.168.8.43(ro)
    That is, all other PCs within hrothgar (on the 192.168.8 "internal" network) are given access to the CDROM on the master PC.

  3. Actually export the CDROM drive by executing the command

    /usr/sbin/exportfs
    from the command line prompt.

The edits above will mount and export the CDROM drive the next time the master PC is rebootted. Alternately, the command:

mount /mnt/cdrom
will mount the CDROM drive now, and a df command should produce a listing like:
[root@hrothgar /etc]# df Filesystem 1024-blocks Used Available Capacity Mounted on /dev/hda1 1018392 316001 649775 33% / /dev/hda5 1844892 27948 1721589 2% /scratch00 /dev/hdb 624736 624736 0 100% /mnt/cdrom

Remark: In principle, the manipulations just described can be done through a GUI. After logging in as root, enter the startx command to begin the fvwm X-window manager and then click on the File System Configuration button at the bottom of the control panel. Personally, we found direct edits of the configuration files to be easier.

Activating The Second Ethernet Card

The instructions in the Master Linux Loading document configure the first ethernet connection into the Master PC ("eth0") to be on the external LAN. The second ethernet line ("eth1") must next be activated and linked with the remaining PCs through the ethernet switch.

This is most easily done through the Network Configuration button of the root control panel (logged on as root and running the X-windows system). This should open a Network Configurator panel, with four buttons (Names, Hosts, Interfaces, Routing) across the top. Click on the Interfaces button, which will open the Interface Configuration Panel. A generic sample of this panel is shown here.

Typical Interface Configuration Control Panel

Aside from obvious differences in network numbers, the actual Interface Control panel seen on the PC should look similar, except that the third line should begin with eth1, not eth0.

Warning: If the control panel does not have an entry for both eth0 and eth1, then the system did not recognize both ethernet cards on the Master PC. This must be fixed before continuing with the Beowulf installation. See the RedHat Installation Manual and other on-line documents at the RedHat site for help.

Assuming that a line for eth1 shows up in the panel, the steps to configure the interface are simple (using the network number assignments described in the Know Your Network section of the Preliminaries document):

  1. Click on and highlight the eth1 row and then click on the Edit button at the bottom of the panel. This will produce the Edit Ethernet/Bus Interface panel seen in the figure.

  2. Enter the IP Address (192.168.8.40) and Netmask (255.255.255.0) values for the interface.

  3. Click on the Activate interface at boot time button - so the interface will come up on all subsequent system boots.

  4. Make sure the interface protocol selector reads none.

  5. Click on the Done button to close the Edit panel.

  6. With the eth1 row of the main panel still highlighted, click on the Activate button at the bottom of the panel to activate the interface.

To confirm that the interface is now active, go to (or open) an xterm window and enter the command:

/sbin/ifconfig
After entries for lo and eth0, an entry for the new eth1 should look something like the following:
eth1 Link encap:Ethernet HWaddr 00:A0:C9:85:56:3D inet addr:192.168.8.40 Bcast:192.168.8.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:480341 errors:0 dropped:0 overruns:0 TX packets:116020 errors:0 dropped:0 overruns:0 Interrupt:9 Base address:0xff40
(with, presumably, far smaller counts for the number of transmitted and received packets!)

At this point, the new ethernet card/interface should be connected to the switch and the remaining PCs should also be connected to the switch using 100baseT cables.

The /home File System

As discussed in the Know Your NFS/File Strategy section of the Preliminaries document, the disk management model on the hrothgar system puts user home directories onto the /scratch00 partition of the Master PC (see the Disk Formatting section of the Master Loading document). To make these accessible through the more usual names (/home/joshua, /home/gretchen, etc.), the following commands were executed as root:

cd /home tar cvf home.tar * | Move the existing /home to /scratch00 mv home.tar /scratch00 cd /scratch00 tar xvf home.tar rm home.tar cd / | Remove old /home /bin/rm -r home ln -s scratch00 home | Create symbolic link

Installing and Operating Minicom

The individual PCs within the hrothgar system are connected through a 100baseT Bay Networks BayStack 350T switch. This device includes reasonable configuration and diagnostic software, which can be accessed via a serial console port on the back of the switch. The Master PC was configured to talk to the switch as follows:

  1. As root, enter the command modemtool. This produces a simple dialogue window. Select cua0 (COM1: under MS-DOS) as the serial port.

  2. Connect the Console port on the BayStack box to Serial2 on the back of the Master PC (took some trial and error experiments to determine which serial port was actually COM1).

  3. As root, enter the command minicom -s. This will produce the configuration panel:
    l-----[configuration]------| | Filenames and paths | | File transfer protocols | | Serial port setup | | Modem and dialing | | Screen and keyboard | | Save setup as dfl | | Save setup as.. | | Exit | | Exit from Minicom | ----------------------------
    Toggle down to Serial port setup, hit return, and set the value for option E - Bps/Par/Bits to 9600 8N1. Return to the menu, and select Exit. This starts communications with the switch. After a ^C or two to wake things up, the basic BayStack configuration menu should appear:
    BayStack 350T Main Menu IP Configuration... SNMP Configuration... System Characteristics... Switch Configuration... Service Port Configuration... Spanning Tree Configuration... TELNET Configuration... Software Download... Display Event Log Reset Reset to Default Settings Logout Use arrow keys to highlight option, press or to select option.

    The Switch Configuration option from the main menu provides (among other things) data on the actual packet traffic rates through the switch.