501 lines
9.4 KiB
HTML
501 lines
9.4 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>Control Messages</TITLE
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CONTENT="Modular DocBook HTML Stylesheet Version 1.57"><LINK
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TITLE="C News"
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TITLE="Miscellaneous Files"
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><TR
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><TH
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>Linux Network Administrators Guide</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="x-087-2-cnews.misc.html"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 21. C News</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="x-087-2-cnews.nfs.html"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="X-087-2-CNEWS.CONTROL"
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>21.8. Control Messages</A
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></H1
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><P
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>
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The Usenet news protocol knows a special category of articles that
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evoke certain responses or actions by the news system. These are called
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<I
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CLASS="EMPHASIS"
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>control</I
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> messages. They are recognized by the presence of a
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<TT
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CLASS="REPLACEABLE"
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><I
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>Control:</I
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></TT
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> field in the article header, which contains the
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name of the control operation to be performed. There are several types of them,
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all of which are handled by shell scripts located in
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<TT
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CLASS="FILENAME"
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>/usr/lib/news/ctl</TT
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>.</P
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><P
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>Most of these messages perform their action automatically at the time the article
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is processed by C News without notifying the newsmaster. By default, only
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<SPAN
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CLASS="SYSTEMITEM"
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>checkgroups</SPAN
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> messages will be handed
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to the newsmaster, but you may change this by editing the scripts.</P
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="X-087-2-CNEWS.CONTROL.CANCEL"
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>21.8.1. The cancel Message</A
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></H2
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><P
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>
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The most widely known message is <SPAN
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CLASS="SYSTEMITEM"
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>cancel</SPAN
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>, with which a user can cancel an
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article sent earlier. This effectively removes the article from the
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spool directories, if it exists. The <SPAN
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CLASS="SYSTEMITEM"
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>cancel</SPAN
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> message is forwarded to all sites
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that receive news from the groups affected, regardless of whether the
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article has been seen already. This takes into account the possibility
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that the original article has been delayed over the cancellation
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message. Some news systems allow users to cancel other people's
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messages; this is, of course, a definite no-no.</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="X-087-2-CNEWS.CONTROL.ADDGROUP"
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>21.8.2. newgroup and rmgroup</A
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></H2
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><P
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>
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Two messages dealing with creation or removal of newsgroups are the
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<SPAN
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CLASS="SYSTEMITEM"
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>newgroup</SPAN
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> and
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<SPAN
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CLASS="SYSTEMITEM"
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>rmgroup</SPAN
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> messages. Newsgroups below the
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“usual” hierarchies may be created only after a discussion and
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voting has been held among Usenet readers. The rules applying to the
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<SPAN
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CLASS="SYSTEMITEM"
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>alt</SPAN
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> hierarchy allow for something
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close to anarchy. For more information, see the regular postings in
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<SPAN
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CLASS="SYSTEMITEM"
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>news.announce.newusers</SPAN
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> and
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<SPAN
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CLASS="SYSTEMITEM"
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>news.announce.newgroups</SPAN
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>. Never send
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a <SPAN
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CLASS="SYSTEMITEM"
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>newgroup</SPAN
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> or
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<SPAN
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CLASS="SYSTEMITEM"
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>rmgroup</SPAN
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> message yourself unless you
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definitely know that you are allowed to.</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="X-087-2-CNEWS.CONTROL.CHECKGROUPS"
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>21.8.3. The checkgroups Message</A
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></H2
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><P
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>
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<SPAN
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CLASS="SYSTEMITEM"
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>checkgroups</SPAN
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> messages are sent by news
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administrators to make all sites within a network synchronize their
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<TT
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CLASS="FILENAME"
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>active</TT
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> files with the realities of Usenet. For example,
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commercial Internet Service Providers might send out such a message to their
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customers' sites. Once a month, the “official”
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<SPAN
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CLASS="SYSTEMITEM"
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>checkgroups</SPAN
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> message for the major
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hierarchies is posted to
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<SPAN
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CLASS="SYSTEMITEM"
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>comp.announce.newgroups</SPAN
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> by its
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moderator. However, it is posted as an ordinary article, not as a control
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message. To perform the <SPAN
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CLASS="SYSTEMITEM"
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>checkgroups</SPAN
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>
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operation, save this article to a file, say <TT
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CLASS="FILENAME"
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>/tmp/check</TT
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>,
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remove everything up to the beginning of the control message itself, and feed
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it to the <SPAN
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CLASS="SYSTEMITEM"
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>checkgroups</SPAN
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> script using the
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following command:
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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># <TT
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CLASS="USERINPUT"
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><B
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>su news -c "/usr/lib/news/ctl/checkgroups" < /tmp/check</B
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></TT
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></PRE
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></TD
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></TR
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></TABLE
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></P
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><P
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>This will update your <TT
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CLASS="FILENAME"
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>newsgroups</TT
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> file from the new list
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of groups, adding the groups
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listed in <TT
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CLASS="FILENAME"
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>localgroups</TT
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>. The old
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<TT
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CLASS="FILENAME"
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>newsgroups</TT
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> file will be moved to
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<TT
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CLASS="FILENAME"
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>newsgroups.bac</TT
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>. Note that posting the message locally
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rarely works, because <B
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CLASS="COMMAND"
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>inews</B
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>, the command that accepts
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and posts articles from users, refuses to accept that large an article.</P
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><P
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>If C News finds mismatches between the
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<SPAN
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CLASS="SYSTEMITEM"
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>checkgroups</SPAN
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> list and the
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<TT
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CLASS="FILENAME"
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>active</TT
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> file, it produces a list of commands that
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would bring your site up to date and mails it to the news administrator. </P
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><P
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>The output typically looks like this:
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>From news Sun Jan 30 16:18:11 1994
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Date: Sun, 30 Jan 94 16:18 MET
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From: news (News Subsystem)
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To: usenet
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Subject: Problems with your active file
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The following newsgroups are not valid and should be removed.
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alt.ascii-art
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bionet.molbio.gene-org
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comp.windows.x.intrisics
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de.answers
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You can do this by executing the commands:
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/usr/lib/news/maint/delgroup alt.ascii-art
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/usr/lib/news/maint/delgroup bionet.molbio.gene-org
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/usr/lib/news/maint/delgroup comp.windows.x.intrisics
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/usr/lib/news/maint/delgroup de.answers
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The following newsgroups were missing.
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comp.binaries.cbm
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comp.databases.rdb
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comp.os.geos
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comp.os.qnx
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comp.unix.user-friendly
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misc.legal.moderated
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news.newsites
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soc.culture.scientists
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talk.politics.crypto
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talk.politics.tibet</PRE
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></TD
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></TR
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></TABLE
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></P
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><P
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>When you receive a message like this from your news system, don't
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believe it automatically. Depending on who sent the
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<SPAN
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CLASS="SYSTEMITEM"
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>checkgroups</SPAN
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> message, it may lack a few
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groups or even entire hierarchies; you should be careful about removing
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any groups. If you find groups are listed as missing that you want to carry
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at your site, you have to add them using the <B
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CLASS="COMMAND"
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>addgroup</B
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>
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script. Save the list of missing groups to a file and feed it to the
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following little script:
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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>#!/bin/sh
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#
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WHOIAM=`whoami`
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if [ "$WHOIAM" != "news" ]
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then
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echo "You must run $0 as user 'news'" >&2
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exit 1
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fi
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#
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cd /usr/lib/news
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while read group; do
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if grep -si "^$group[[:space:]].*moderated" newsgroup; then
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mod=m
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else
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mod=y
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fi
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/usr/lib/news/maint/addgroup $group $mod
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done</PRE
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></TD
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></TR
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></TABLE
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> </P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="X-087-2-CNEWS.CONTROL.SENDSYS"
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>21.8.4. sendsys, version, and senduuname</A
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></H2
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><P
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> Finally, there are three messages that can be used to find out about
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the network's topology. These are <SPAN
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CLASS="SYSTEMITEM"
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>sendsys</SPAN
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>, <SPAN
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CLASS="SYSTEMITEM"
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>version</SPAN
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>, and <SPAN
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CLASS="SYSTEMITEM"
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>senduuname</SPAN
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>. They cause C News to return
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the <TT
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CLASS="FILENAME"
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>sys</TT
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> file to the sender, as well as a software
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version string and the output of <B
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CLASS="COMMAND"
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>uuname</B
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>,
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respectively. C News is very laconic about <SPAN
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CLASS="SYSTEMITEM"
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>version</SPAN
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> messages; it returns a simple,
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unadorned <TT
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CLASS="LITERAL"
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>C</TT
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>.</P
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><P
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>Again, you should <I
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CLASS="EMPHASIS"
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>never</I
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> issue such a message unless you
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have made sure that it cannot leave your (regional) network. Replies to
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<SPAN
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CLASS="SYSTEMITEM"
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>sendsys</SPAN
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> messages can quickly bring down
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a UUCP network.<A
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NAME="X-087-2-FNCN09"
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HREF="#FTN.X-087-2-FNCN09"
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>[1]</A
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></P
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></DIV
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></DIV
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><H3
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CLASS="FOOTNOTES"
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>Notes</H3
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><TABLE
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BORDER="0"
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CLASS="FOOTNOTES"
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WIDTH="100%"
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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WIDTH="5%"
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><A
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NAME="FTN.X-087-2-FNCN09"
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HREF="x-087-2-cnews.control.html#X-087-2-FNCN09"
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>[1]</A
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></TD
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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WIDTH="95%"
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><P
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>I wouldn't try this on the Internet, either.</P
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></TD
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></TR
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></TABLE
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
|
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><A
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HREF="x-087-2-cnews.misc.html"
|
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="index.html"
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>Home</A
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="x-087-2-cnews.nfs.html"
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>Next</A
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>Miscellaneous Files</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="x-087-2-cnews.html"
|
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>Up</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
|
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>C News in an NFS Environment</TD
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></TR
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></TABLE
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