UUCP /etc/uucp/Systems File
The /etc/uucp/Systems file contains the information that is needed by the uucico daemon to establish a communication link to a remote computer. /etc/uucp/Systems is the first file that you need to edit to configure UUCP.
Each entry in the Systems file represents a remote computer with which your host communicates. A particular host can have more than one entry. The additional entries represent alternative communication paths that are tried in sequential order. In addition, by default UUCP prevents any computer that does not appear in /etc/uucp/Systems from logging in to your host.
By using the Sysfiles file, you can define several files to be used as Systems files. See UUCP /etc/uucp/Sysfiles File for a description of Sysfiles.
System-Name Time Type Speed Phone Chat ScriptExample 26-1 Entry in /etc/uucp/Systems
Arabian Any ACUEC 38400 111222 ogin: Puucp ssword:beledi
System-Name Field in /etc/uucp/Systems File
This field contains the node name of the remote computer. On TCP/IP networks, this name can be the machine's host name or a name that is created specifically for UUCP communications through the /etc/uucp/Sysname file. See UUCP /etc/uucp/Systems File. In Example 26-1, the System-Name field contains an entry for remote host Arabian.
Time Field in /etc/uucp/Systems File
day Portion of Time Field
time Portion of Time Field
Example 26-1 shows Any in the Time field, which indicates that host Arabian can be called at any time.
The time portion should be a range of times that are specified in 24-hour notation, for example, 0800-1230 for 8:30 a.m. to 12:30 p.m. If no time portion is specified, any time of day is assumed to be allowed for the call.
A time range that spans 0000 is permitted. For example, 0800-0600 means all times are allowed other than times between 6 a.m. and 8 a.m.
retry Portion of Time Field
The retry subfield enables you to specify the minimum time (in minutes) before a retry, following a failed attempt. The default wait is 60 minutes. The subfield separator is a semicolon (;). For example, Any;9 is interpreted as call any time, but wait at least 9 minutes before retrying after a failure occurs.
If you do not specify a retry entry, an exponential back-off algorithm is used. This means that UUCP starts with a default wait time that grows larger as the number of failed attempts increases. For example, suppose the initial retry time is 5 minutes. If no response occurs, the next retry is 10 minutes later. The next retry is 20 minutes later, and so on until the maximum retry time of 23 hours is reached. If retry is specified, the value specified is always the retry time. Otherwise, the back-off algorithm is used.
Type Field in /etc/uucp/Systems File
This field contains the device type that should be used to establish the communication link to the remote computer. The keyword that is used in this field is matched against the first field of Devices file entries.Example 26-2 Keyword With the Type Field
Arabian Any ACUEC, g 38400 1112222 ogin: Puucp ssword:beledi
You can define the protocol that is used to contact the system by adding the protocol to the Type field. The previous example shows how to attach the protocol g to the device type ACUEC. For information about protocols, see Protocol Definitions in /etc/uucp/Devices File.
Speed Field in /etc/uucp/Systems File
This field, also known as the Class field, specifies the transfer speed of the device that is used in establishing the communication link. The UUCP speed field can contain a letter and speed, such as C1200 or D1200, to differentiate between classes of dialers. Refer to Class Field in the /etc/uucp/Devices File.Example 26-3 Entry in Speed Field
eagle Any ACU, g D1200 NY3251 ogin: nuucp ssword:Oakgrass
Phone Field in /etc/uucp/Systems File
This field enables you to specify the telephone number, known as a token, of the remote computer for automatic dialers, which are known as port selectors. The telephone number consists of an optional alphabetic abbreviation and a numeric part. If an abbreviation is used, the abbreviation must be listed in the Dialcodes file.Example 26-4 Entry in the Phone Field
nubian Any ACU 2400 NY555-1212 ogin: Puucp ssword:Passuan eagle Any ACU, g D1200 NY=3251 ogin: nuucp ssword:Oakgrass
In the Phone field, an equal sign (=) instructs the ACU to wait for a secondary dial tone before dialing the remaining digits. A dash (-) in the string instructs the ACU to pause four seconds before dialing the next digit.
If your computer is connected to a port selector, you can access other computers that are connected to that selector. The Systems file entries for these remote machines should not have a telephone number in the Phone field. Instead, this field should contain the token to be passed to the switch. In this way, the port selector knows the remote machine with which your host wants to communicate, usually just the system name. The associated Devices file entry should have a \D at the end of the entry to ensure that this field is not translated by using the Dialcodes file.
Chat-Script Field in /etc/uucp/Systems File
This field, also known as the Login field, contains a string of characters that is called a chat-script. The chat script contains the characters the local and remote machines must pass to each other in their initial conversation. Chat scripts have the following format:
expect send [expect send] ....
expect represents the string that the local host expects to receive from the remote host to initiate conversation. send is the string that the local host sends after the local host receives the expect string from the remote host. A chat script can have more than one expect-send sequence.
The -send is sent if the prior expect is not successfully read. The -expect that follows the -send is the next expected string.
For example, with strings login--login, the UUCP on the local host expects login. If UUCP receives login from the remote machine, UUCP goes to the next field. If UUCP does not receive login, UUCP sends a carriage return, then looks for login again. If the local computer initially does not expect any characters, use the characters "", for NULL string, in the expect field. All send fields are sent with a carriage return appended unless the send string is terminated with a \c.
The following is an example of a Systems file entry that uses an expect-send string:
sonora Any ACUEC 9600 2223333 "" \r \r ogin:-BREAK-ogin: Puucpx ssword:xyzzy
This example instructs UUCP on the local host to send two carriage returns and wait for ogin: (for Login:). If ogin: is not received, send a BREAK. When you do receive ogin:, send the login name Puucpx. When you receive ssword: (for Password:), send the password xyzzy.
Table 26-1 Escape Characters Used in the Chat-Script Field of the Systems File
Enabling Dialback Through the Chat Script
Some companies set up dial-in servers to handle calls from remote computers. For example, your company might have a dial-in server with a dialback modem that employees can call from their home computers. After the dial-in server identifies the remote machine, the dial-in server disconnects the link to the remote machine and then calls back the remote machine. The communications link is then reestablished.
You can facilitate dialback by using the \H option in the Systems file chat script at the place where dialback should occur. Include the \H as part of an expect string at the place where the dial-in server is expected to hang up.
For example, suppose the chat script that calls a dial-in server contains the following string:
The UUCP dialing facility on the local machine expects to receive the characters, INITIATED, from the dial-in server. After the characters, INITIATED, have been matched, the dialing facility flushes any subsequent characters that the dialing facility receives until the dial-in server hangs up. The local dialing facility then waits until it receives the next part of the expect string, the characters ogin:, from the dial-in server. When it receives the ogin:, the dialing facility then continues through the chat script.
Hardware Flow Control in /etc/uucp/Systems File
You can also use the pseudo-send STTY=value string to set modem characteristics. For instance, STTY=crtscts enables hardware flow control. STTY accepts all stty modes. See the stty(1) and termio(7I) man pages for complete details.
The following example enables hardware flow control in a Systems file entry:
unix Any ACU 2400 12015551212 "" \r ogin: Puucp ssword:Passuan "" \ STTY=crtscts
Setting Parity in /etc/uucp/Systems File
In some situations, you have to reset the parity because the system that you are calling checks port parity and drops the line if it is wrong. The expect-send couplet, "" P_ZERO, sets the high-order bit (parity bit) to 0. See this expect-send couplet in the following example:
unix Any ACU 2400 12015551212 "" P_ZERO "" \r ogin: Puucp ssword:Passuan
The following are parity couplets that can follow the expect-send couplet, "" P_ZERO:
These parity couplets can be inserted anywhere in the chat script. The parity couplets apply to all information in the chat script that follows "" P_ZERO, the expect-send couplet. A parity couplet can also be used in entries in the Dialers file. The following example includes the parity couplet, "" P_ONE:
unix Any ACU 2400 12015551212 "" P_ZERO "" P_ONE "" \r ogin: Puucp ssword:Passuan