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Chapter 27 UUCP ReferenceThis chapter provides reference information for working with UUCP. The following topics are covered: UUCP /etc/uucp/Systems FileThe /etc/uucp/Systems file contains the information needed by the uucico daemon to establish a communication link to a remote computer. It is the first file 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. 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. Each entry in the Systems file has the following format:
The following example shows the fields of the Systems file. Example 27-1 Fields in /etc/uucp/Systems
UUCP System-Name FieldThis field contains the node name of the remote computer. On TCP/IP networks, this can be the machine's host name or a name created specifically for UUCP communications through the /etc/uucp/Sysname file. See "UUCP /etc/uucp/Systems File". In Example 27-1, the System-Name field contains an entry for remote host arabian. UUCP Time FieldThis field specifies the day of week and time of day when the remote computer can be called. The format of the Time field is: daytime[;retry] The day portion can be a list containing some of the following entries: Table 27-1 Day Field
Example 27-1 shows Any in the Time field, indicating that host arabian can be called at any time. The time portion should be a range of times specified in 24-hour notation. (Example: 0800-1230 for 8:30 AM to 12:30 PM.) 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 AM and 8 AM. UUCP Retry SubfieldThe 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. What this means is 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 there is no response, 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, that is always the retry time. Otherwise, the back-off algorithm is used. UUCP Type FieldThis field contains the device type that should be used to establish the communication link to the remote computer. The keyword used in this field is matched against the first field of Devices file entries. Example 27-2 Type Field and /etc/uucp/Devices File
You can define the protocol used to contact the system by adding it on to the Type field. The previous example shows how to attach the protocol g to the device type ACUEC. (For information on protocols, see "UUCP Protocol Definitions in the Devices File".) UUCP Speed FieldThis field (also known as the Class field) specifies the transfer speed of the device used in establishing the communication link. It can contain a letter and speed (for example, C1200, D1200) to differentiate between classes of dialers (refer to "UUCP Class Field"). Some devices can be used at any speed, so the keyword Any can be used. This field must match the Class field in the associated Devices file entry: Example 27-3 Speed Field and /etc/uucp/Devices File
If information is not required for this field, use a dash (-) as a place holder for the field. UUCP Phone FieldThis field allows you to specify the telephone number (token) of the remote computer for automatic dialers (port selectors). The telephone number consists of an optional alphabetic abbreviation and a numeric part. If an abbreviation is used, it must be one that is listed in the Dialcodes file: Example 27-4 Phone Field Correspondence
In the System-Name string, an equals sign (=) tells 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 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 on to the switch. In this way, the port selector knows the remote machine with which your host wants to communicate. (This is 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 using the Dialcodes file. UUCP Chat-Script FieldThis field (also called the Login field) contains a string of characters 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 format: expect send [expect send] .... expect represents the string that the local host expects to get from the remote host to initiate conversation. send is the string the local host sends after it receives the expect string from the remote host. A chat-script can have more than one expect-send sequence. A basic chat-script might contain:
The expect field can be made up of subfields of the form: expect[-send-expect]... where -send is sent if the prior expect is not successfully read, and -expect following the send is the next expected string. For example, with strings login--login, the UUCP on the local host expects login. If UUCP gets login from the remote machine, it goes to the next field. If it does not get login, it sends a carriage return, then looks for login again. If the local computer initially does not expect any characters, use the characters "" (NULL string) in the expect field. All send fields are sent followed by a carriage return unless the send string is terminated with a \c. Here is an example of a Systems file entry that uses an expect-send string:
This example tells 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 get ogin: send the login name Puucpx. When you get ssword: (for Password:), send the password xyzzy. The following table lists some useful escape characters. Table 27-2 Escape Characters Used in Systems File Chat-Script
Enabling Dialback Through the Chat-ScriptSome 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, it disconnects the link to the remote machine and then calls the remote machine back. 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 get the characters INITIATED from the dial-in server. After the INITIATED characters have been matched, the dialing facility flushes any subsequent characters it 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. You need not have a string of characters directly preceding or following the \H, as shown in the previous sample string. UUCP Hardware Flow ControlYou 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 would enable hardware flow control in a Systems file entry:
This pseudo-send string can also be used in entries in the Dialers file. UUCP Setting ParityIn some cases, 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. For example:
In the same manner, P_EVEN sets parity to even (the default), P_ODD sets odd parity, and P_ONE sets the parity bit to 1. The parity couplet can be inserted anywhere in the chat-script. It applies to all information in the chat-script following the "" P_ZERO. It can also be used in entries in the Dialers file. UUCP /etc/uucp/Devices FileThe /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 includes modern, high-speed modems--direct links, and network connections. Here is an entry in /etc/uucp/Devices for a US Robotics V.32bis modem attached to port A and running at 38,400 bps.
Each field is described in the next section. UUCP Type FieldThis field describes the type of link that the device establishes. It can contain one of the keywords described in the sections that follow. Direct KeywordThe 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. Make a separate entry for each line that you want to reference through the -l option of cu. ACU KeywordThe ACU keyword indicates that the link to a remote computer (whether through cu, UUCP, or PPP) is made through a modem. This modem can be connected either directly to your computer or indirectly through a port selector. Port SelectorThis is a variable that is replaced in the Type field by the name of a port selector. Port selectors are devices attached to a network that prompt 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.) Sys-NameThis 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 to an entry in /etc/uucp/Systems for the computer Sys-Name. Type Field and /etc/uucp/Systems FileExample 27-5 shows a comparison between the fields in /etc/uucp/Devices and fields in /etc/uucp/Systems. The titles of each column apply only to fields in the Devices file. The keyword 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 case a V.32bis modem. This value is matched against the third field in the Systems file, which also contains the entry ACUEC. (See "UUCP /etc/uucp/Systems File" for more information.) Example 27-5 Type Field and /etc/uucp/Systems File Equivalent
UUCP Line FieldThis field contains the device name of the line (port) associated with the Devices entry. For instance, if the modem associated with a particular entry were attached to the /dev/cua/a device (serial port A), the name 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:
UUCP Line2 FieldThis field is a placeholder. Always use a dash (-) here. 801 type dialers, which are not supported in the Solaris environment, use the Line2 field. Non-801 dialers do not normally use this configuration, but still require a hyphen in this field. UUCP Class FieldThe Class field contains the speed of the device, if the keyword ACU or Direct is used in the Type field. However, it can contain a letter and a speed (for example, C1200, D1200) to differentiate between classes of dialers (Centrex or Dimension PBX). This 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 handles the external communications. In such a case, it becomes necessary to distinguish which line(s) should be used for internal communications and which should be used for external communications. The keyword used in the Class field of the Devices file is matched against the Speed field of Systems file. Example 27-6 UUCP Class Field
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 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. UUCP Dialer-Token-Pairs FieldThe 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 not present, it is taken from a related entry in the Systems file. The token portion can be supplied immediately following the dialer portion. The last dialer token pair might not be present, depending on the associated dialer. In most cases, 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 table shows the special dialer types. Table 27-3 Dialer-Token Pairs
See "UUCP Protocol Definitions in the Devices File" for more information. Structure of the Dialer-Token-Pairs FieldThe DTP field can be structured four different ways, depending on the device associated with the entry:
Example 27-7 Dialers Field for Direct Connect Modem
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 case the phone number) is taken from the Phone field of a Systems file entry. (\T is implied, as described in Example 27-9.)
Example 27-8 UUCP Dialers Field for Computers on Same Port Selector
As shown, the token portion is left blank. This 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".) This type of DTP contains an escape character (\D), which ensures that the contents of the Phone field not interpreted as a valid entry in the Dialcodes file.
Example 27-9 UUCP Dialers Field for Modems Connected to Port Selector
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 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, where Ventel is the dialer and the token is retrieved from the Systems file. Two escape characters can appear in a DTP field:
UUCP Protocol Definitions in the Devices FileYou can define the protocol to use with each device in /etc/uucp/Devices. This 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".) If you do specify the protocol, you must use the 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 27-4 Protocols Used in /etc/uucp/Devices
Here is an example showing a protocol designation for a device entry:
This example indicates that, for device TCP, try to use the t protocol. If the other end 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. UUCP /etc/uucp/Dialers FileThe /etc/uucp/Dialers file contains dialing instructions for many commonly used modems. You probably do not need to change or add entries to this file unless you plan to use a nonstandard modem or plan to customize your UUCP environment. Nevertheless, you should understand what is in the file and how it relates to the Systems and Devices file. The text specifies the initial conversation that must take place on a line before it can be made available for transferring data. This conversation, often referred to as a chat-script, is usually a sequence of ASCII strings that is transmitted and expected, and it is often used to dial a phone number. As shown in the examples in "UUCP /etc/uucp/Devices File", the fifth field in a Devices file entry is an index into the Dialers file or a special dialer type (TCP, TLI, or TLIS). The uucico daemon attempts to match the fifth field in the Devices file with the first field of each Dialers file entry. In addition, each odd-numbered Devices field, starting with the seventh position is used as an index into the Dialers file. If the match succeeds, the Dialers entry is interpreted to perform the dialer conversation. Each entry in the Dialers file has the following format:
The following example shows the entry for a US Robotics V.32bis modem. Example 27-10 /etc/uucp/Dialers File Entry
The Dialer field matches the fifth and additional odd-numbered fields in the Devices file. The Substitutions field is a translate string: the first of each pair of characters is mapped to the second character in the pair. This is usually used to translate = and - into whatever the dialer requires for "wait for dial tone" and "pause." The remaining expect-send fields are character strings. The following example shows some sample entries in the Dialers file, as distributed when you install UUCP as part of the Solaris installation program. Example 27-11 Excerpts From /etc/uucp/Dialers
The following table lists escape characters commonly used in the send strings in the Dialers file. Table 27-5 Backslash Characters for /etc/uucp/Dialers
Here is a penril entry in the Dialers file:
First, the substitution mechanism for the phone number argument is established, so that any = is replaced with a W (wait for dial tone) and any - with a P (pause). The handshake given by the remainder of the line works as listed:
UUCP Hardware Flow ControlYou can also use the pseudo-send STTY=value string to set modem characteristics. For instance, STTY=crtscts enables outbound hardware flow control; STTY=crtsxoff enables inbound hardware flow control; and STTY=crtscts,crtsxoff enables both outbound and inbound hardware flow control. STTY accepts all the stty modes. See the stty(1) and termio(7I) man pages. The following example would enable hardware flow control in a Dialers entry:
This pseudo-send string can also be used in entries in the Systems file. UUCP Setting ParityIn some cases, 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 parity to zero:
In the same manner, P_EVEN sets it to even (the default); P_ODD sets it to odd; and P_ONE sets it to one. This pseudo-send string can also be used in entries in the Systems file. Other Basic UUCP Configuration FilesThe files in this section can be used in addition to the Systems, Devices, and Dialers file when doing basic UUCP configuration. UUCP /etc/uucp/Dialcodes FileThe /etc/uucp/Dialcodes file enables you to define dial-code abbreviations that can be used in the Phone field in the /etc/uucp/Systems file. You can use the Dialcodes files to provide additional information about a basic phone number that is used by several systems at the same site. Each entry has the format: abbreviation dial-sequence where abbreviation represents the abbreviation used in the Phone field of the Systems file and dial-sequence represents the dial sequence passed to the dialer when that particular Systems file entry is accessed. The following table shows the correspondences between the two files. Table 27-6 Correspondences Between Dialcodes and Systems Files
The following table contains sample entries in a Dialcodes file. Table 27-7 Entries in the Dialcodes File
In the first row, NY is the abbreviation to appear in the Phone field of the Systems file. For example, the Systems file might have the entry: NY5551212 When uucico reads NY in the Systems file, it searches the Dialcodes file for NY and obtains the dialing sequence 1=212. This is the dialing sequence needed for any phone call to New York City. It includes the number 1, an equal sign (=) meaning pause and wait for a secondary dial tone, and the area code 212. uucico sends this information to the dialer, then returns to the Systems file for the remainder of the phone number, 5551212. The entry jt 9=847- would work with a Phone field in the Systems file such as jt7867. When uucico reads the entry containing jt7867 in the Systems file, it sends the sequence 9=847-7867 to the dialer, if the token in the dialer-token pair is \T. UUCP /etc/uucp/Sysfiles FileThe /etc/uucp/Sysfiles file lets you assign different files to be used by uucp and cu as Systems, Devices, and Dialers files. (For more information on cu, see the cu(1C) man page.) You might want to use Sysfiles for:
The format of the Sysfiles file is:
w represents uucico, cu, or both separated by a colon. x represents one or more files to be used as the Systems file, with each file name separated by a colon and read in the order presented. y represents one or more files to be used as the Dialers file. z is one or more files to be used as the Devices file. Each file name is assumed to be relative to the /etc/uucp directory, unless a full path is given. The following sample, /etc/uucp/Sysfiles defines a local Systems file (Local_Systems) in addition to the standard /etc/uucp/Systems file:
When this entry is in /etc/uucp/Sysfiles, both uucico and cu first check in the standard /etc/uucp/Systems. If the system they are trying to call doesn't have an entry in that file, or if the entries in the file fail, then they look in /etc/uucp/Local_Systems. Given the previous entry, cu and uucico share the Dialers and Devices files. When different Systems files are defined for uucico and cu services, your machine stores two different lists of Systems. You can print the uucico list using the uuname command or the cu list using the uuname -C command. Another example of the file, where the alternate files are consulted first and the default files are consulted in case of need is:
UUCP /etc/uucp/Sysname FileEvery machine that uses UUCP must have an identifying name, often referred to as the node name. This is the name that appears in the remote machine's /etc/uucp/Systems file, along with the chat-script and other identifying information. Normally, UUCP uses the same node name as is returned by the uname -n command, which is also used by TCP/IP. You can specify a UUCP node name independent of the TCP/IP host name by creating the /etc/uucp/Sysname file. The file has a one-line entry containing the UUCP node name for your system. UUCP /etc/uucp/Permissions FileThe /etc/uucp/Permissions file specifies the permissions that remote computers have with respect to login, file access, and command execution. Some options restrict the remote computer's ability to request files and its ability to receive files queued by the local machine. Another option is available that specifies the commands that a remote machine can execute on the local computer. UUCP Structuring EntriesEach entry is a logical line, with physical lines terminated by a backslash (\) to indicate continuation. Entries are made up of options delimited by blank space. Each option is a name-value pair in the following format: name=value Values can be colon-separated lists. No blank space is allowed within an option assignment. Comment lines begin with a pound sign (#), and they occupy the entire line up to a newline character. Blank lines are ignored (even within multiple-line entries). The types of Permissions file entries are:
Note - When a remote machine calls you, its identity is questionable unless it has a unique login and verifiable password.
LOGNAME entries contain a LOGNAME option and MACHINE entries contain a MACHINE option. One entry can contain both options. UUCP ConsiderationsWhen using the Permissions file to restrict the level of access granted to remote computers, you should consider the following:
UUCP REQUEST OptionWhen a remote computer calls your computer and requests to receive a file, this request can be granted or denied. The REQUEST option specifies whether the remote computer can request to set up file transfers from your computer. The string REQUEST=yes specifies that the remote computer can request to transfer files from your computer. The string REQUEST=no specifies that the remote computer cannot request to receive files from your computer. This is the default value; it is used if the REQUEST option is not specified. The REQUEST option can appear in either a LOGNAME (remote computer calls you) entry or a MACHINE (you call remote computer) entry. UUCP SENDFILES OptionWhen a remote computer calls your computer and completes its work, it can attempt to take work your computer has queued for it. The SENDFILES option specifies whether your computer can send the work queued for the remote computer. The string SENDFILES=yes specifies that your computer can send the work that is queued for the remote computer as long as itis logged in as one of the names in the LOGNAME option. This string is mandatory if you have entered Never in the Time field of /etc/uucp/Systems. This designation sets up your local machine in passive mode; it is not allowed to initiate a call to this particular remote computer. (See "UUCP /etc/uucp/Systems File" for more information.) The string SENDFILES=call specifies that files queued in your computer are sent only when your computer calls the remote computer. The call value is the default for the SENDFILES option. This option is only significant in LOGNAME entries because MACHINE entries apply when calls are made out to remote computers. If the option is used with a MACHINE entry, it is ignored. UUCP MYNAME OptionThis option enables you to designate a unique UUCP node name for your computer in addition to its TCP/IP host name, as returned by the hostname command. For instance, if you have unknowingly given your host the same name as that of some other system, you might want to set the MYNAME option of the Permissions file. Or if you want your organization to be known as widget but all your modems are connected to a machine with the host name gadget, you can have an entry in gadget's Permissions file that says:
Now the system world can log in to the machine gadget as if it were logging in to widget. In order for machine world to know you also by the aliased name widget when you call it, you can have an entry that says:
You can also use the MYNAME option for testing purposes, as it allows your machine to call itself. However, because this option could be used to mask the real identity of a machine, you should use the VALIDATE option, as described in "UUCP VALIDATE Option". UUCP READ and WRITE OptionsThese options specify the various parts of the file system that uucico can read from or write to. You can designate READ and WRITE options with either MACHINE or LOGNAME entries. The default for both the READ and WRITE options is the uucppublic directory, as shown in the following strings:
The strings READ=/ and WRITE=/ specify permission to access any file that can be accessed by a local user with Other permissions. The value of these entries is a colon-separated list of path names. The READ option is for requesting files, and the WRITE option is for depositing files. One of the values must be the prefix of any full path name of a file coming in or going out. To grant permission to deposit files in /usr/news as well as the public directory, use the following values with the WRITE option:
If the READ and WRITE options are used, all path names must be specified because the path names are not added to the default list. For instance, if the /usr/news path name were the only one specified in a WRITE option, permission to deposit files in the public directory would be denied. Be careful which directories you make accessible for reading and writing by remote systems. For example, the /etc directory contains many critical system files; remote users should not have permission to deposit files in this directory. UUCP NOREAD and NOWRITE OptionsThe NOREAD and NOWRITE options specify exceptions to the READ and WRITE options or defaults. The entry:
permits reading any file except those in the /etc directory (and its subdirectories--remember, these are prefixes). It permits writing only to the default /var/spool/uucppublic directory. NOWRITE works in the same manner as the NOREAD option. You can use the NOREAD and NOWRITE options in both LOGNAME and MACHINE entries. UUCP CALLBACK OptionYou can use the CALLBACK option in LOGNAME entries to specify that no transaction takes place until the calling system is called back. The two reasons to set up CALLBACKare: For security purposes; if you call back a machine, you can be sure it is the right machine. For accounting purposes; if you are doing long data transmissions, you can choose the machine that is billed for the longer call. The string CALLBACK=yes specifies that your computer must call the remote computer back before any file transfers can take place. The default for the CALLBACK option is CALLBACK=no. If you set CALLBACK to yes, the permissions that affect the rest of the conversation must be specified in the MACHINE entry corresponding to the caller. Do not specify these permissions in the LOGNAME, or in the LOGNAME entry that the remote machine might have set for your host. Note - If two sites have the CALLBACK option set for each other, a conversation never gets started. UUCP COMMANDS OptionThe COMMANDS option can compromise the security of your system. Use it with extreme care. You can use the COMMANDS option in MACHINE entries to specify the commands that a remote computer can execute on your machine. The uux program generates remote execution requests and queues them to be transferred to the remote computer. Files and commands are sent to the target computer for remote execution. This is an exception to the rule that MACHINE entries apply only when your system calls out. Note that COMMANDS is not used in a LOGNAME entry; COMMANDS in MACHINE entries defines command permissions, whether you call the remote system or it calls you. The string COMMANDS=rmail specifies the default commands that a remote computer can execute on your computer. If a command string is used in a MACHINE entry, the default commands are overridden. For instance, the entry:
overrides the COMMAND default so that the computers named owl, raven, hawk, and dove can now execute rmail, rnews, and lp on your computer. In addition to the names as just specified, there can be full path names of commands. For example:
specifies that command rmail uses the default search path. The default search path for UUCP is /bin and /usr/bin. When the remote computer specifies rnews or /usr/local/rnews for the command to be executed, /usr/local/rnews is executed regardless of the default path. Likewise, /usr/local/lp is the lp command that is executed. Including the ALL value in the list means that any command from the remote computers specified in the entry will be executed. If you use this value, you give the remote computers full access to your machine. This allows far more access than normal users have. You should use this value only when both machines are at the same site, are closely connected, and the users are trusted. The string:
illustrates two points:
You should use the VALIDATE option whenever you specify potentially dangerous commands like cat and uucp with the COMMANDS option. Any command that reads or writes files is potentially dangerous to local security when executed by the UUCP remote execution daemon (uuxqt). UUCP VALIDATE OptionUse the VALIDATE option in conjunction with the COMMANDS option whenever you specify commands that are potentially dangerous to your machine's security. (VALIDATE is merely an added level of security on top of the COMMANDS option, though it is a more secure way to open command access than ALL.) VALIDATE provides a certain degree of verification of the caller's identity by cross-checking the host name of a calling machine against the login name it uses. The string:
ensures that if any machine other than widget or gadget tries to log in as Uwidget, the connection is refused. The VALIDATE option requires privileged computers to have a unique login and password for UUCP transactions. An important aspect of this validation is that the login and password associated with this entry are protected. If an outsider gets that information, that particular VALIDATE option can no longer be considered secure. Carefully consider which remote computers you will grant privileged logins and passwords for UUCP transactions. Giving a remote computer a special login and password with file access and remote execution capability is like giving anyone on that computer a normal login and password on your computer. Therefore, if you cannot trust someone on the remote computer, do not provide that computer with a privileged login and password. The LOGNAME entry:
specifies that if one of the remote computers that claims to be eagle, owl, or hawk logs in on your computer, it must have used the login uucpfriend. If an outsider gets the uucpfriend login and password, masquerading is easy. But what does this have to do with the COMMANDS option, which appears only in MACHINE entries? It links the MACHINE entry (and COMMANDS option) with a LOGNAME entry associated with a privileged login. This link is needed because the execution daemon is not running while the remote computer is logged in. In fact, it is an asynchronous process that does not know which computer sent the execution request. Therefore, the real question is, how does your computer know where the execution files came from? Each remote computer has its own spool directory on your local machine. These spool directories have write permission given only to the UUCP programs. The execution files from the remote computer are put in its spool directory after being transferred to your computer. When the uuxqt daemon runs, it can use the spool directory name to find the MACHINE entry in the Permissions file and get the COMMANDS list. Or, if the computer name does not appear in the Permissions file, the default list is used. This example shows the relationship between the MACHINE and LOGNAME entries:
The value in the COMMANDS option means that remote users can execute rmail and /usr/local/rnews. In the first entry, you must assume that when you want to call one of the computers listed, you are really calling either eagle, owl, or hawk. Therefore, any files put into one of the eagle, owl, or hawk spool directories is put there by one of those computers. If a remote computer logs in and says that it is one of these three computers, its execution files are also put in the privileged spool directory. You therefore have to validate that the computer has the privileged login uucpz. UUCP MACHINE Entry for OTHERYou might want to specify different option values for remote machines that are not mentioned in specific MACHINE entries. The need might arise when many computers are calling your host, and the command set changes from time to time. The name OTHER for the computer name is used for this entry as shown in this example:
All other options available for the MACHINE entry can also be set for the computers that are not mentioned in other MACHINE entries. Combining MACHINE and LOGNAME Entries for UUCPYou can combine MACHINE and LOGNAME entries into a single entry where the common options are the same. For example, the two entries:
and:
share the same REQUEST, READ, and WRITE options. You can merge them, as shown:
Combining MACHINE and LOGNAME entries makes the Permissions file more manageable and efficient. UUCP ForwardingWhen sending files through a series of machines, the intermediary machines must have the command uucp among their COMMANDS options. If you type the command:
the forwarding operation works only if machine willow permits machine oak to execute the program uucp, and if machine oak permits your machine to do the same. The machine pine, being the last machine designated, does not have to permit the command uucp since it is not doing any forwarding operations. Machines are not normally set up this way. UUCP /etc/uucp/Poll FileThe /etc/uucp/Poll file contains information for polling remote computers. Each entry in the Poll file contains the name of a remote computer to call, followed by a tab character or a space, and finally the hours the computer should be called. The format of entries in the Poll file are: sys-name hour ... For example, the entry
provides polling of computer eagle every four hours. The uudemon.poll script processes the Poll file but does not actually perform the poll. It merely sets up a polling work file (always named C.file) in the spool directory. The uudemon.poll script starts the scheduler, and the scheduler examines all work files in the spool directory. UUCP /etc/uucp/Config FileThe /etc/uucp/Config file enables you to override certain parameters manually. Each entry in the Config file has this format: parameter=value See the Config file provided with your system for a complete list of configurable parameter names. The following Config entry sets the default protocol ordering to Gge and changes the G protocol defaults to 7 windows and 512-byte packets.
UUCP/etc/uucp/Grades FileThe /etc/uucp/Grades file contains the definitions for the job grades that can be used to queue jobs to a remote computer. It also contains the permissions for each job grade. Each entry in this file represents a definition of an administrator-defined job grade that lets users queue jobs. Each entry in the Grades file has the following format: User-job-grade System-job-grade Job-size Permit-type ID-list Each entry contains fields that are separated by blank space. The last field in the entry is made up of subfields also separated by spaces. If an entry takes up more than one physical line, you can use a backslash to continue the entry onto the following line. Comment lines begin with a pound sign (#) and occupy the entire line. Blank lines are always ignored. UUCP User-job-grade FieldThis field contains an administrative-defined user job grade name of up to 64 characters. UUCP System-job-grade FieldThis field contains a one-character job grade to which User-job-grade is mapped. The valid list of characters is A-Z, a-z, with A having the highest priority and z the lowest. Relationship Between User and System Job GradesThe user job grade can be bound to more than one system job grade. It is important to note that the Grades file is searched sequentially for occurrences of a user job grade. Therefore, any multiple occurrences of a system job grade should be listed according to the restriction on the maximum job size. While there is no maximum number for the user job grades, the maximum number of system job grades allowed is 52. The reason is that more than one User-job-grade can be mapped to a System-job-grade, but each User-job-grade must be on a separate line in the file. Here is an example:
Given this configuration in a Grades file, these two User-job-grade will share the same System-job-grade. Because the permissions for a Job-grade are associated with a User-job-grade and not a System-job-grade, two User-job-grades can share the same System-job-grades and have two different sets of permissions. Default GradeYou can define the binding of a default User-job-grade to a system job grade. You must use the keyword default as user job grade in the User-job-grade field of the Grades file and the system job grade that it is bound to. The Restrictions and ID fields should be defined as Any so that any user and any size job can be queued to this grade. Here is an example:
If you do not define the default user job grade, the built-in default grade Z is used. Because the restriction field default is Any, multiple occurrences of the default grade are not checked. UUCP Job-size FieldThis field specifies the maximum job size that can be entered in the queue. Job-size is measured in bytes and can be a list of the options listed shown in the following table: Table 27-8 Job-size Field
Here are some examples:
UUCP Permit-type FieldThis field contains a keyword that denotes how to interpret the ID list. The following table lists the keywords and their meanings. Table 27-9 Permit-type Field
UUCP ID-list FieldThis field contains a list of login names or group names that are to be permitted or denied queuing to this job grade. The list of names are separated by a blank space and terminated by a newline character. The keyword Any is used to denote that anyone is permitted to queue to this job grade. Other UUCP Configuration FilesThis section describes three less-frequently modified files that impact the use of UUCP facilities. UUCP /etc/uucp/Devconfig FileThe /etc/uucp/Devconfig file enables you to configure devices by service--uucp or cu. Devconfig entries define the STREAMS modules that are used for a particular device. They have the format: service=x device=y push=z[:z...] x can be cu, uucico, or both separated by a colon. y is the name of a network and must match an entry in the Devices file. z is replaced by the names of STREAMS modules in the order that they are to be pushed onto the Stream. Different modules and devices can be defined for cu and uucp services. The following entries are for a STARLAN network and would most commonly be used in the file:
This example pushes ntty, then tirdwr. UUCP /etc/uucp/Limits FileThe /etc/uucp/Limits file controls the maximum number of simultaneous uucicos, uuxqts, and uuscheds that are running in the uucp networking. In most cases, the default values are fine and no changes are needed. If you want to change them, however, use any text editor. The format of the Limits file is: service=x max=y: x can be uucico, uuxqt or uusched, and y is the limit permitted for that service. The fields can be in any order and in lowercase. The following entries should most commonly be used in the Limits file:
The example allows five uucicos, five uuxqts, and two uuscheds running on your machine. UUCP remote.unknown FileThe other file that affects the use of communication facilities is the remote.unknown file. This file is a binary program that executes when a machine not found in any of the Systems files starts a conversation. It logs the conversation attempt and drops the connection. If you change the permissions of the remote.unknown file so it cannot execute, your system accepts connections from any system. This program executes when a machine that is not in any of the Systems starts a conversation. It logs the conversation attempt but fails to make a connection. If you change the permissions of this file so it cannot execute (chmod 000 remote.unknown), your system accepts any conversation requests. This is not a trivial change, and you should have good reasons for doing it. UUCP Administrative FilesThe UUCP administrative files are described next. These files are created in spool directories to lock devices, hold temporary data, or keep information about remote transfers or executions.
These files can remain in the spool directory if the communications link is unexpectedly dropped (usually on computer crashes). The lock file is ignored (removed) after the parent process is no longer active. The lock file contains the process ID of the process that created the lock.
UUCP Error MessagesThis section lists the error messages associated with UUCP. UUCP ASSERT Error MessagesThe following table lists ASSERT error messages. Table 27-11 ASSERT Error Messages
UUCP STATUS Error MessagesThe following table is a list of the most common STATUS error messages. Table 27-12 UUCP STATUS Messages
UUCP Numerical Error MessagesThe following table lists the exit code numbers of error status messages produced by the /usr/include/sysexits.h file. Not all are currently used by uucp. Table 27-13 UUCP Error Messages by Number
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