Analysis of UUCP function in Unix operating system

UNIX operating system has a lot to learn from the place, here we mainly introduce the UNIX operating system in the UUCP, let's study together! The UUCP system is a set of programs that completes file transfer, performs commands between systems, maintains system usage statistics, and protects security.

UUCP is the most widely used network Utility system for two reasons:

* First, UUCP is the only standard network system available for all UNIX operating system versions

* Second, UUCP is the cheapest network system. Only one cable is required to connect the two systems, and then the UUCP can be built. If you need to transfer data between two systems that are hundreds of or thousands of kilometers away, you need two modems with dial-up capabilities.

1 Unix Operating system UUCP command

One of the UUCP commands is UUCP, which is used for file transfers between two systems, and the UUCP command format is similar to the format of the CP command, except that UUCP allows the user to copy files between systems, the general format of the command is as follows:

Source_file is usually a UNIX operating system file but not necessarily, destination_file is usually a file or directory of another system. The format of the specified Destination_file is:

UUCP provides system administrators with an option to restrict UUCP files that are passed in and out of the UNIX operating system to the/USR/SPOOL/UUCPPUBLIC directory structure. If you tell UUCP that the transferred file is stored in a different directory, the system will send back a:

UUCP allows the simplification of symbols ~ to replace/usr/spool/uucppublic/.

Sometimes you can also use UUCP to copy files from another system to a UNIX operating system, as long as the file you want to pass into this system is designated as a source file with System!file, such as:

The previous command cannot be copied to a file if the file transfer directory is restricted on a remote machine. The safest way to copy files to this system is to file transfer through the Uucppublic directory on both systems:

2 Uux Command

The Uux command can be used to execute commands on another UNIX operating system, a feature called remote Command ren line. The most common use of Uux is to send mail between systems to execute uux within it. Typical Uux requests are as follows:

This command formats the file listing and then connects to the Remote1 printer PR1 on the UNIX operating system. Uux option "-" enables Uux to establish the standard input device for this command as a remote command Standard input devices. When only one system in several systems is connected to a printer, a common Uux prints the file.

Of course, remote command hospitality must be strictly restricted to protect system security. For example: This system should not allow users on other systems to run the following command:

This command will enable the UNIX operating system to transfer/etc/passwd files to the system outside, generally, only a few commands are allowed to execute. Rmail is a restricted mail program that is often executed to allow through Uux One of the commands. Also allows rnews netnews pseudo offline commands to be executed on systems running Netnews, and LP to run on systems that provide print devices.

3 Uucico Program

Instead of calling another system and transferring files and executing commands, the UUCP and Uux commands queue the user's request and start the Uucico program. Uucico completes the actual communication work. It calls other systems, logs in, The transfer data can be a file or request remote command execution. If the phone line is busy, or if other Unix operating systems are shut down, the transfer request remains in the queue, and uucico subsequent functional operations are typically cron-completed to send these transfer requests.

Uucico completes the sending and receiving of data. In the/etc/passwd file of the system, there are uucico logins for other systems entering entry into the system, and the default shell specified in the entry entry is Uucico. Therefore, when other systems call this system, they directly talk to Uucico.

4 UUXQT Program

When the Uucico of another system requests a remote command execution, Uucico of the system queues the request and initiates the UUXQT program to execute a remote command request before exiting.