System Administration Guide: Network Services

UUCP /etc/uucp/Devices File

The /etc/uucp/Devices file contains information for all the devices that can be used to establish a link to a remote computer. These devices include ACUs (which include high-speed modems), direct links, and network connections.

An entry in the /etc/uucp/Devices file has the following syntax:

Type   Line   Line2   Class   Dialer-Token-Pairs

The following is an entry in the Devices file for a U.S. Robotics V.32bis modem that is attached to port A and is running at 38,400 bps.

ACUEC   cua/a   -   38400   usrv32bis-ec

Entry in the Type field. For more information, see Type Field in /etc/uucp/Devices File.


Entry in the Line field. For more information, see Line Field in the /etc/uucp/Devices File.


Entry in the Line2 field. For more information, see Line2 Field in the /etc/uucp/Devices File.


Entry in the Class field. For more information, see Class Field in the /etc/uucp/Devices File.


Entry in the Dialer-Token-Pairs field. For more information, see Dialer-Token-Pairs Field in the /etc/uucp/Devices File.

Each field is described in the next section.

Type Field in /etc/uucp/Devices File

This field describes the type of link that the device establishes. The UUCP Type field can contain one of the keywords that is described in the sections that follow.

Direct Keyword

The Direct keyword appears mainly in entries for cu connections. This keyword indicates that the link is a direct link to another computer or a port selector. Create a separate entry for each line that you want to reference through the -l option of cu.

ACU Keyword

The ACU keyword indicates that the link to a remote computer (whether through cu, UUCP, asppp, or Solaris PPP 4.0) is made through a modem. This modem can be connected either directly to your computer or indirectly through a port selector.

Port Selector

The port selector is a variable that is replaced in the Type field by the name of a port selector. Port selectors are devices that are attached to a network that prompts for the name of a calling modem, then grant access. The file /etc/uucp/Dialers contains caller scripts only for the micom and develcon port selectors. You can add your own port selector entries to the Dialers file. See UUCP /etc/uucp/Dialers File for more information.

System-Name Variable

This variable is replaced by the name of a machine in the Type field, indicating that the link is a direct link to this particular computer. This naming scheme is used to associate the line in this Devices entry with an entry in /etc/uucp/Systems for the computer System-Name.

Type Fields in Devices File and Systems File

Example 26–5 shows a comparison of the fields in /etc/uucp/Devices and the fields in /etc/uucp/Systems. The keyword that is used in the Type field of the Devices file is matched against the third field of the Systems file entries. In the Devices file, the Type field has the entry ACUEC, indicating an automatic call unit, in this instance a V.32bis modem. This value is matched against the Type field in the Systems file, which also contains the entry ACUEC. See UUCP /etc/uucp/Systems File for more information.

Example 26–5 Comparison of Type Fields in Devices file and Systems File

The following is an example of an entry in the Devices file.

ACUEC cua/a - 38400 usrv32bis-ec

The following is an example of an entry in the Systems file.

Arabian Any ACUEC 38400 111222 ogin: Puucp ssword:beledi

Line Field in the /etc/uucp/Devices File

This field contains the device name of the line (known as port) that is associated with the Devices entry. If the modem that is associated with a particular entry were attached to the /dev/cua/a device (serial port A), the name that is entered in this field would be cua/a. An optional modem control flag, M, can be used in the Line field to indicate that the device should be opened without waiting for a carrier. For example:


Line2 Field in the /etc/uucp/Devices File

This field is a placeholder. Always use a hyphen (-) here. 801–type dialers, which are not supported in the Solaris OS, use the Line2 field. Non-801 dialers do not normally use this configuration, but still require a hyphen in this field.

Class Field in the /etc/uucp/Devices File

The Class field contains the speed of the device, if the keyword ACU or Direct is used in the Type field. However, the Class field can contain a letter and a speed, such as C1200 or D1200, to differentiate between classes of dialers, such as Centrex or Dimension PBX.

This differentiation is necessary because many larger offices can have more than one type of telephone network. One network might be dedicated to serving only internal office communications while another network handles the external communications. In such a situation, you must distinguish which line or lines should be used for internal communications and which should be used for external communications.

The keyword that is used in the Class field of the Devices file is matched against the Speed field of the Systems file.

Example 26–6 Class Field in the Devices file

ACU   cua/a   -   D2400  hayes

Some devices can be used at any speed, so the keyword Any can be used in the Class field. If Any is used, the line matches any speed that is requested in the Speed field of the Systems file. If this field is Any and the Systems file Speed field is Any, the speed defaults to 2400 bps.

Dialer-Token-Pairs Field in the /etc/uucp/Devices File

The Dialer-Token-Pairs (DTP) field contains the name of a dialer and the token to pass it. The DTP field has this syntax:

dialer token [dialer token]

The dialer portion can be the name of a modem, a port monitor, or it can be direct or uudirect for a direct-link device. You can have any number of dialer-token pairs. If the dialer portion is not present, it is taken from a related entry in the Systems file. The token portion can be supplied immediately after the dialer portion.

The last dialer-token pair might not be present, depending on the associated dialer. In most situations, the last pair contains only a dialer portion. The token portion is retrieved from the Phone field of the associated Systems file entry.

A valid entry in the dialer portion can be defined in the Dialers file or can be one of several special dialer types. These special dialer types are compiled into the software and are therefore available without having entries in the Dialers file. The following list shows the special dialer types.


TCP/IP network


Transport Level Interface Network (without STREAMS)


Transport Level Interface Network (with STREAMS)

See Protocol Definitions in /etc/uucp/Devices File for more information.

Structure of the Dialer-Token-Pairs Field in the /etc/uucp/Devices File

The DTP field can be structured four different ways, depending on the device that is associated with the entry.

See the first way that the DTP field can be structured:

Directly connected modem – If a modem is connected directly to a port on your computer, the DTP field of the associated Devices file entry has only one pair. This pair would normally be the name of the modem. This name is used to match the particular Devices file entry with an entry in the Dialers file. Therefore, the Dialer field must match the first field of a Dialers file entry.

Example 26–7 Dialers Field for Directly Connect Modem

Dialers   hayes =,-,  ""          \\dA\pTE1V1X1Q0S2=255S12=255\r\c 
                                  \EATDT\T\r\c CONNECT

Notice that only the dialer portion (hayes) is present in the DTP field of the Devices file entry. This means that the token to be passed on to the dialer (in this instance, the phone number) is taken from the Phone field of a Systems file entry. (\T is implied, as described in Example 26–9.)

See the second and third ways that the DTP field can be structured:

Example 26–8 UUCP Dialers Field for Computers on Same Port Selector

Dialers    develcon ,""   ""            \pr\ps\c est:\007 \E\D\e \007

As shown, the token portion is left blank. This designation indicates that it is retrieved from the Systems file. The Systems file entry for this computer contains the token in the Phone field, which is normally reserved for the phone number of the computer. Refer to UUCP /etc/uucp/Systems File for details. This type of DTP contains an escape character (\D), which ensures that the content of the Phone field is not interpreted as a valid entry in the Dialcodes file.

See the fourth way that the DTP field can be structured:

Modems that are connected to port selector – If a high-speed modem is connected to a port selector, your computer must first access the port selector switch. The switch makes the connection to the modem. This type of entry requires two dialer-token-pairs. The dialer portion of each pair (the fifth and seventh fields of the entry) is used to match entries in the Dialers file, as follows.

Example 26–9 UUCP Dialers Field for Modems Connected to Port Selector

develcon ""     ""    \pr\ps\c  est:\007    \E\D\e      \007
ventel   =&-%   t""   \r\p\r\c  $           <K\T%\r>\c  ONLINE!

In the first pair, develcon is the dialer and vent is the token that is passed to the Develcon switch to tell it which device, such as a Ventel modem, to connect to your computer. This token is unique for each port selector, as each switch can be set up differently. After the Ventel modem has been connected, the second pair is accessed. Ventel is the dialer and the token is retrieved from the Systems file.

Two escape characters can appear in a DTP field:

Protocol Definitions in /etc/uucp/Devices File

You can define the protocol to use with each device in /etc/uucp/Devices. This specification is usually unnecessary because you can use the default or define the protocol with the particular system you are calling. Refer to UUCP /etc/uucp/Systems File for details. If you do specify the protocol, you must use the following form:

Type,Protocol [parameters]

For example, you can use TCP,te to specify the TCP/IP protocol.

The following table shows the available protocols for the Devices file.

Table 26–2 Protocols Used in /etc/uucp/Devices




This protocol is commonly used for transmissions over TCP/IP and other reliable connections. t assumes error-free transmissions.


This protocol is UUCP's native protocol. g is slow, reliable, and good for transmission over noisy telephone lines.


This protocol assumes transmission over error-free channels that are message oriented, as opposed to byte-stream oriented, such as TCP/IP.  


This protocol is used for transmission over X.25 connections. f relies on flow control of the data stream and is meant for working over links that can (almost) be guaranteed to be error free, specifically X.25/PAD links. A checksum is enacted over a whole file only. If a transport fails, the receiver can request retransmission or retransmissions.

Here is an example that shows a protocol designation for a device entry:

TCP,te - - Any TCP - 

This example indicates that, for device TCP, you should try to use the t protocol. If the other end of the transmission refuses, use the e protocol.

Neither e nor t is appropriate for use over modems. Even if the modem assures error-free transmission, data can still be dropped between the modem and the CPU.