Jak cię złapią, to znaczy, że oszukiwałeś. Jak nie, to znaczy, że posłużyłeś się odpowiednią taktyką.
On the other hand, the newsgroups exchanged may be limited by both the sending or receiving system. The set of newsgroups and distributions allowed
for transmission to a site are usually kept in the sys le. The sheer number of articles usually requires that improvements be made to the above scheme. On UUCP networks, the natural thing to do is to collect articles over a period of time, and combine them into a single le, which is compressed and sent to the remote site. This is called batching.3 An alternative technique is the ihave/sendme protocol that prevents duplicate articles from being transferred in the rst place, thus saving net bandwidth. Instead of putting all articles in batch les and sending them along, only the message ids of articles are combined 2 Wait a moment: 60 Megs at 9600 bps, that's 60 million by 1200, that is mutter, mutter, Hey! That's : : : : : : 34 hours! 3 The golden rule of netnews, according to Geo Collyer: \Thou shalt batch thine articles." 16.3. How Does Usenet Handle News? 274 into a giant \ihave" message and sent to the remote site. It reads this message, compares it to its history le, and returns the list of articles it wants in a \sendme" message. Only these articles are then sent. Of course, ihave/sendme only makes sense if it involves two big sites that receive news from several independent feeds each, and who poll each other often enough for an ecient ow of news. Sites that are on the Internet generally rely on TCP/IP-based software that uses the Network News Transfer Protocol, NNTP. It transfers news between feeds and provides 4 Usenet access to single users on remote hosts. NNTP knows three dierent ways to transfer news. One is a real-time version of ihave/sendme, also referred to as pushing news. The second technique is called pulling news, in which the client requests a list of articles in a given newsgroup or hierarchy that have arrived at the server's site after a specied date, and chooses those it cannot nd in its history le. The third mode is for interactive newsreading, and allows you or your newsreader to retrieve articles from specied newgroups, as well as post articles with incomplete header information. At each site, news are kept in a directory hierarchy below /var/spool/news, each arti- cle in a separate le, and each newsgroup in a separate directory. The directory name is made up of the newsgroup name, with the components being the path components. Thus, comp.os.linux.misc articles are kept in /var/spool/news/comp/os/linux/misc. The arti- cles in a newsgroup are assigned numbers in the order they arrive. This number serves as the le's name. The range of numbers of articles currently online is kept in a le called active, which at the same time serves as a list of newsgroups known at your site. Since disk space is a nite resource, one has to start throwing away articles after some 5 time. This is called expiring. Usually, articles from certain groups and hierarchies are expired at a xed number of days after they arrive. This may be overridden by the poster by specifying a date of expiration in the Expires: eld of the article header. 4 Described in RFC 977. 5 Some people claim that Usenet is a conspiracy by modem and hard disk vendors. Chapter 17 C News One of the most popular software packages for Netnews is C News. It was designed for sites that carry news over UUCP links. This chapter will discuss the central concepts of C News, and the basic installation and maintenance tasks. C News stores its conguration les in /usr/lib/news, and most of its binaries in the /usr/lib/news/bin directory. Articles are kept below /var/spool/news. You should make sure virtually all les in these directories are owned by user news, group news. Most problems arise from les being inaccessible to C News. Make it a rule for you to become user news using su before you touch anything in there. The only exceptions is setnewsids, which is used to set the real user id of some news programs. It must be owned by root and must have the setuid bit set. In the following, we describe all C News conguration les in detail, and show you what
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