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Installing a Modem

This section describes how to install a modem onto a serial port. It describes how to set up the hardware and software to support a UUCP modem connection. (Refer to the Serial Device Manager in the System Manager for a GUI-based approach to the tasks discussed in this section.)

Topics in this section are

Silicon Graphics is compatible with most industry-standard modems. This section uses the US Robotics Sportster and Telebit modems as examples for the installation procedure. If you are using another type of modem, substitute its information where applicable.

You can use the standard system software to set up a modem for three different modes:

If you want to set up your modem for a SLIP or PPP connection, complete the modem configuration steps in the chapter and then refer to the SLIP or PPP configuration procedures in IRIX Admin: Networking and Mail.

Before You Begin

There are a few prerequisites you should be aware of before installing the modem. Review the following points before installing the modem.

Warning: Be sure you are not violating a site security policy by installing a modem on your system. If your system is networked to other systems, access to your system by modem provides a potential point of unauthorized access to the entire network.

Setting Up the Modem Software

The major tasks for setting up the modem software are similar, no matter how you choose to use your modem.

Table 1-2 provides an overview of the major tasks for each of the three usage modes. An "x" in the table denotes that the task is performed.

Overview of Modem Software Setup
TaskDial-In
Only
Dial-Out
Only
Dial-In/
Dial-Out
Turn off the port
in /etc/inittab
xxx
Execute telinit q to
reinitialize the port
xxx
Run fix-modem
configuration script
xxx
Edit Devices file xx
Chown device to uucp xx
Update action field in /etc/inittabx x

Modem Software Setup, All Modes

The installation procedure in this section is used to start the software setup for the three usage modes. Follow the procedure until you reach the section that is specific for the usage mode you have chosen. Then continue with that section. For example, if you are configuring your modem for dial-in only, complete the procedures in this section and the "Dial-In Mode" section.

  1. Log in as root.

  2. Edit /etc/inittab to turn off the port you will be using for your modem so that you can configure it correctly.

    Find the line for the port. The line begins with tportnumber, where portnumber is the number of a serial port. For example, if you connected your modem to port 2, look for a line similar to the following:

    t2:23:respawn:/etc/getty -N ttyd2 co_9600 #port 2

    Change respawn to off. This tells the system not to restart the /etc/getty program when it exits. If it is already off, continue to the next step. The line should look like this when you are finished:

    t2:23:off:/etc/getty -N ttyd2 co_9600 #port 2

  3. Write and exit the /etc/inittab file.

  4. Inform init about the change to inittab with the following command:

    telinit q

  5. Run the modem configuration script for your modem type (see Table 1-1). Select the appropriate argument for its usage mode from Table 1-3 for the port you are configuring.

    Determining the Usage Mode for Modem Configuration
    Dial-InDial-OutDial-In/Dial-Out
    -i-o-io

    Note: Be sure to view the entire configuration script for information and command arguments specific to your modem type before running the script.

    For example, if you want to configure a US Robotics Sportster modem for dial-in/dial-out connected to port 2, use the fix-usr command and specify a dial-in/dial-out argument (-io) and the port number to which the modem is connected. For example, enter the command

    /etc/uucp/fix-usr -io 2

    You can also specify the optional modem model type and the modem speed using the command

    /etc/uucp/fix-usr -io -m SPORT -s 38400 2

    As another example, to configure a Telebit modem for dial-in only mode, use the fix-telebit command and specify a dial-in modem (-i), the model of the modem (tb+, t1000, t1600, t2500) and its speed, and the port number to which the modem is connected.

    In this example, if a T2500 modem is connected to port 2 at 19,200 baud, dial-in only, enter the following command:

    /etc/uucp/fix-telebit -i -m t2500 -s 19200 2

Dial-Out Mode

This section describes additional steps for configuring dial-out only and dial-in/dial-out modems. Be sure you have completed the steps in "Modem Software Setup, All Modes" before starting the setup in this section.

You turn on dial-out modem software by editing the /etc/uucp/Devices file. You also have to change ownership of the port to UUCP.

  1. Edit the /etc/uucp/Devices file to specify the port to which the modem is connected and to set the correct baud rate for the modem. Also, add a direct line for use in debugging problems. The lines have the following forms:

    ACU ttynportnumber null baud 212 x dialer
    Direct ttydportnumber - baud direct

  2. Change the ownership of the device files. For example, if you are using serial port 2, give the following command (substituting the appropriate tty device as determined above):

    chown uucp /dev/tty[dfm]2

When you have finished the above process, try to dial out through the modem to verify the dial-out setup, as described in "Dialing Out to Another Modem". For more information on dialer options, see the file /etc/uucp/Dialers.

Dial-In Mode

Be sure you have completed the steps in "Modem Software Setup, All Modes". For dial-in/dial-out mode, be sure you have also completed the steps in "Dial-Out Mode".

Complete the configuration by editing the file /etc/inittab. Perform the following steps:

  1. Edit the file /etc/inittab again so that the system recognizes that the port is used for the modem (as opposed to a terminal). This editing also sets the interface speed on the port and enables user logins through the port.

    Find the line for the port to which the modem is connected. The line begins with tportnumber, where portnumber is the number of a serial port. For example, if you connected your modem to port 2, look for a line similar to the following:

    t2:23:off:/etc/getty -N ttyd2 co_9600 #port 2

    Make the following changes to this line:

  2. Write and exit the /etc/inittab file.

  3. Inform init about the change to /etc/inittab with the following command:

    telinit q

To test the dial-in setup, have someone try to dial in to the system through this modem.

To dial out through the modem to verify the dial-out setup, continue with the section "Dialing Out to Another Modem."

Timing Out a Dial-In Connection

There is no standard way to configure the system to time out dial-in connections after a set amount of time. One way to accomplish this, however, is by using a shell for the dial-in account that supports time-outs after a specified period (for example, tcsh).

Warning: You should not change root's shell to /usr/bin/tcsh if /usr is a separate filesystem because it may not be mounted in single-user mode.

Note: The tcsh timeout does not work for dial-in connections that use PPP, SLIP, or UUCP.

Alternatively, you could write a script that determines the length of time a user is logged in and acts accordingly (refer to last(1), grep(1), and who(1) for more information).

Dialing Out to Another Modem

The cu utility dials your modem. Before you attempt to dial out, make sure your local modem is connected to both your system and a working telephone line. Also, make sure the modem is turned on. The cu syntax to dial the number 1-800-555-1234 is

cu 18005551234

Refer to the cu(1C) reference page for complete information on cu. If everything is working, you should hear the modem dialing and after a short time you should see the following message on your console:

Connected


Before You Begin
Setting Up the Modem Software
Modem Software Setup, All Modes
Dial-Out Mode
Dial-In Mode
Timing Out a Dial-In Connection
Dialing Out to Another Modem

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