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.Thus, if wehad put !rec.games.go after rec, all articles from this group would have been threaded nevertheless.nn offers several methods to remove expired articles from its databases.The first is to update thedatabase by scanning the newsgroup directories and discarding the entries whose corresponding articlehas exceeded its expiration date.This is the default operation obtained by invoking nnmaster with theE option.It is reasonably quick, unless you're doing this via NNTP.The second method behaves exactly like a default expiration run of mthreads; it removes only thoseentries that refer to articles with numbers below the low-water mark in the active file.It may beenabled using the e option.Finally, the third strategy discards the entire database and recollects all articles.It may be enabled usingthe E3 option.The list of groups to be expired is given by the F option in the same fashion as above.However, if youhave nnmaster running as daemon, you must kill it (using k) before expiration can take place, andrestart it with the original options afterward.Thus the proper command to run expiration on all groupsusing the first method is: # nnmaster -kF ""# nnmaster -lrCThere are many more flags that fine-tune the nn's behavior.If you are concerned about removing badarticles or assembling article digests, read the nnmaster manual page.nnmaster relies on a file named GROUPS, which is located in /var/lib/nn.If it does not exist whennnmaster is first run, it is created.For each newsgroup, it contains a line that begins with the group'sname, optionally followed by a time stamp and flags.You may edit these flags to enable certain behaviorfor the group in question, but you may not change the order in which the groups appear.[1] The flagsallowed and their effects are detailed in the nnmaster manual page, too.Notes[1] Their order has to agree with that of the entries in the (binary) MASTER file.Prev Home Nexttrn Configuration Up Example Network:The VirtualBrewery[ Please note that the University of Edinburgh is not responsible for the content ofthese WWW pages.For queries please contact user@ph.ed.ac.uk whereuser appears after the ~ and before the / in the URL for this page ] Linux Network Administrators GuidePrev NextAppendix B.Useful Cable ConfigurationsA Serial NULL Modem CableA serial null modem cable will work for both SLIP and PPP.Again, you will need two DB-25connectors.This time your cable requires only eight conductors.You may have seen other NULL modem cable designs, but this one allows you to use hardware flowcontrol which is far superior to XON/XOFF flow control or none at all.The conductor configuration isshown in Figure B-2:Again, if you have a shield, you should connect it to the first pin at one end only.Figure B-1.Parallel PLIP cableFigure B-2.Serial NULL-Modem cable Prev Home NextUseful Cable Configurations Up Linux Network Administrator'sGuide, Second Edition CopyrightInformation[ Please note that the University of Edinburgh is not responsible for the content ofthese WWW pages.For queries please contact user@ph.ed.ac.uk whereuser appears after the ~ and before the / in the URL for this page ] Linux Network Administrators GuidePrev NextChapter 4.Configuring the Serial HardwareIntroduction to Serial DevicesThe Unix kernel provides devices for accessing serial hardware, typically called tty devices (pronouncedas it is spelled: T-T-Y).This is an abbreviation for Teletype device, which used to be one of the majormanufacturers of terminal devices in the early days of Unix.The term is used now for anycharacter-based data terminal.Throughout this chapter, we use the term to refer exclusively to the Linuxdevice files rather than the physical terminal.Linux provides three classes of tty devices: serial devices, virtual terminals (all of which you can accessin turn by pressing Alt-F1 through Alt-Fnn on the local console), and pseudo-terminals (similar to atwo-way pipe, used by applications such as X11).The former were called tty devices because the originalcharacter-based terminals were connected to the Unix machine by a serial cable or telephone line andmodem.The latter two were named after the tty device because they were created to behave in a similarfashion from the programmer's perspective.SLIP and PPP are most commonly implemented in the kernel.The kernel doesn't really treat the ttydevice as a network device that you can manipulate like an Ethernet device, using commands such asifconfig.However, it does treat tty devices as places where network devices can be bound.To do this, thekernel changes what is called the line discipline of the tty device.Both SLIP and PPP are linedisciplines that may be enabled on tty devices.The general idea is that the serial driver handles datagiven to it differently, depending on the line discipline it is configured for.In its default line discipline,the driver simply transmits each character it is given in turn
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