483 lines
16 KiB
HTML
483 lines
16 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<html>
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<head>
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<title>More 2 Cent Tips & Tricks Issue 12</title>
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</head>
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<BODY BGCOLOR=#C0C0C0 TEXT=#000000 LINK=#0000FF VLINK=#0020F0
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ALINK=#FF0000 BACKGROUND="../gx/spirbind.gif">
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<table width=100%>
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<tr><td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H4>"Linux Gazette...<I>making Linux just a little more fun!</I>
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"</H4>
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<P> <hr> <P>
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<!-- QUICK TIPS SECTION ================================================== -->
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<center>
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<H1><A NAME="tips"><IMG ALIGN=MIDDLE ALT="" SRC="../gx/twocent.gif">
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More 2¢ Tips!</A></H1> <BR>
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Send Linux Tips and Tricks to <A HREF="mailto:gazette@ssc.com">
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gazette@ssc.com
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</A></center>
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<p><hr><p>
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<H3>Contents:</H3>
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<ul>
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<li><a HREF="./lg_tips12.html#dmesg">Boot Information Display</a>
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<li><a HREF="./lg_tips12.html#console">Console Tricks</a>
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<li><a HREF="./lg_tips12.html#fire">Firewalling / Masquerading with 2.0.xx</a>
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<li><a HREF="./lg_tips12.html#ftp">FTP and /etc/shells</a>
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<li><a HREF="./lg_tips12.html#adm">How to Truncate /var/adm/messages</a>
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<li><a HREF="./lg_tips12.html#html">HTML, Use of BODY Attributes</a>
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<li><a HREF="./lg_tips12.html#lowerit">lowerit Shell Script</a>
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<li><a HREF="./lg_tips12.html#user">Removing Users</a>
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<li><a HREF="./lg_tips12.html#pass">Root and Passwords</a>
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<li><a HREF="./lg_tips12.html#talk">Talk Daemon and Dynamic Addresses</a>
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<li><a HREF="./lg_tips12.html#tar">tar Tricks</a>
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</ul>
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="dmesg"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="dmesg">
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Boot Information Display
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</a></H3>
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<P>
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Date: Fri, 1 Nov 1996 09:58:52 -0800 (PST)<BR>
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From: Laurie Lynne Tucker <BR>
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<P>
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dmesg | more -- Forget (or couldn't look fast enough) at boot time? This
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command will display your boot information (a.k.a., the "kernel
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ring buffer"). For more info, see the man page.
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="console"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="console">A 2
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Cent Console Trick</a></H3>
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<P>
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Date: Fri, 08 Nov 1996 03:42:27 -0800 <BR>
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From: Igor Markov <A HREF="mailto:imarkov@math.ucla.edu">imarkov@math.ucla.edu</A><BR>
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Organization: UCLA, Department of Mathematics <BR>
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<P>
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Hi,
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<P>
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Here's my 2c console trick: <BR>
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I put the following line into my ~/.xsession file:
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<PRE>
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nxterm -ls -geometry 80x5+45+705 -rv -sb -name "System mesages" -fn 5x7
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-T "System messages" -e tail -f /var/log/messages &
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</PRE>
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and this one into my .fvwm:
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<PRE>
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Style "System messages" NoTitle, Sticky, WindowListSkip
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</PRE>
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When I login, I have a small 5-line (but scrollable) window near
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the left bottom corner (you may need to change numbers in -geometry)
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where system messages appear in tiny font as soon as they are produced.
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This lets me see when my dial-up script succeeds, when someone logs
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into my computer via TCP/IP, when some system error happen etc.
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<P>
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The .fvwm setup strips the title bar and does other useful things,
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but is not necessary.
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<P>
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Caveat: if you leave this window for long time, a cron job which
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trims /var/log/messages will change the inode # for the file and
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tail -f is bound to freeze. In 99% this cron job wakes up 2-3am, so
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tail freeze may freeze only overnight. Login/logout and everything
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will be OK. Any other ideas?
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<P>
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Igor
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<P> <hr> <P>
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<!-- ===================================================================== -->
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</td> </tr> </table>
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<a name="fire"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="fire">Firewalling / Masquerading
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with 2.0.xx</a></H3>
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<P>
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Date: Sat, 2 Nov 1996 10:57:30 -0500 (EST) <BR>
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From: Preston Brown <A HREF="mailto:pbrown@econ.yale.edu">pbrown@econ.yale.edu</A><BR>
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<P>
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Regarding the recent message about not being able to get IP masquerading
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working with 2.0.xx kernels:
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<P>
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First, I *believe* that IP forwarding may have to be enabled for firewall
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support, but I can't say for sure. Suffice to say that I have forwarding,
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firewalling, and masquerading all compiled into my kernel. I have a PPP
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link set up to the outside world, and my local ethernet subnet
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(192.168.2.x) is masquerades so it can talk to the outside world as well.
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<P>
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ipfwadm is used to set up the information (I call it from
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/etc/rc.d/rc.local at boot time):
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<PRE>
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# ip forwarding policies
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ipfwadm -F -p deny ; default policy is to deny
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; forwarding to all hosts.
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ipfwadm -F -a m -S 192.168.2.0/24 ; add an entry for masquerading of
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; my local subnet
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modprobe ip_masq_ftp ; load ftp support module
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</PRE>
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a 'ipfwadm -F -l' (i.e. list all forwarding policies) yields:
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<PRE>
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IP firewall forward rules, default policy: deny
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type prot source destination ports
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acc/m all 192.168.2.0/24 anywhere n/a
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</PRE>
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Indicating that all is fine. Your local subnet now should be set up to
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talk to the outside world just fine.
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<P>
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--- <BR>
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-Preston Brown, preston.brown@yale.edu
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="ftp"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="ftp">FTP and /etc/shells</a></H3>
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<P>
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Date: Fri, 1 Nov 1996 09:58:52 -0800 (PST)<BR>
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From: Laurie Lynne Tucker <BR>
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<P>
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A user's shell must be included in the list at /etc/shells for ftp to
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work!!!!! (by default, you get only /bin/sh and /bin/bash!)
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<P>
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-- <BR>
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laurie
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<P>
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="adm"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="adm">How to Truncate
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/var/adm/messages</a></H3>
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<P>
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Date: Fri, 1 Nov 1996 09:58:52 -0800 (PST)<BR>
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From: Alex
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<P>
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In answer to the question:
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<blockquote>
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What is the proper way to close and reopen a new /var/adm/messages file
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from a running system?
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</blockquote>
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Step one: rename the file. Syslog will still be writing in it after
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renaming so you don't lose messages.
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Step two: create a new one. After re-initializing syslogd it will be
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used.
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Step three: Make syslog use the new file. Do not restart it, just
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re-initialize.
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<ol>
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<li>mv /var/adm/messages /var/adm/messages.prev
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<li>touch /var/adm/messages
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<li>kill -1 pid-of-syslogd
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</ol>
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<P>
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This should work on a decent Unix(like) system, and I know Linux is
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one of them.
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<P>
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="html"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="html">
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HTML, Use of BODY Attributes
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</a></H3>
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<P>
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Date: Thu, 14 Nov 1996 12:55:15 -0500 <BR>
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From: "Michael O'Keefe", <A HREF="mailto:michael.okeefe@lmc.ericsson.se">
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michael.okeefe@lmc.ericsson.se</A><BR>
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Organization: Ericsson Research Canada <BR>
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<P>
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G'day,
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<P>
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If you are going to use any of the attributes to the <BODY> tag, then
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you should supply all of the attributes, even if you supply just the
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default values.
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<P>
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The default <BODY> tag for Netscape, Mosaic and MSIE is
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<BODY BGCOLOR=#C0C0C0 TEXT=#000000 LINK=#0000FF VLINK=#0020F0
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ALINK=#FF0000>
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<P>
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If you wish to slip the BACKGROUND attribute in there, by all means
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continue to do so, but for completeness (and good HTML designing) you
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should supply the other attributes as well.
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<P>
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The reason? You don't know what colors the user has set, and whether
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just setting a BACKGROUND image, or just a few of the colors will
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render the page viewable or not. By supplying all of the values, even
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at their defaults, you ensure that everything contrasts accordingly
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<PRE>
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--
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Michael O'Keefe |Michael.OKeefe@lmc.ericsson.se_
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Lived on and Rode a Honda CBR1000F-H |okeefe@odyssee.net / |
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"It can't rain all the time" |Work:+1 514 345 7900 X5030 / |
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- The Crow - R.I.P. Brandon |Fax :+1 514 345 7980 /_p_|
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My views are MINE ALONE, blah blah, |Home:+1 514 684 8674 \`O'|
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yackety yack - don't come back |Fax :+1 514 684 8674(PCon?)_/_\|_,
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</PRE>
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="lowerit"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="lowerit">"lowerit" Shell Script</a></H3>
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<P>
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Date: Fri, 1 Nov 1996 09:58:52 -0800 (PST)<BR>
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From: Phil Hughes, <A HREF="mailto:phil@ssc.com">phil@ssc.com</A><BR>
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<P>
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Here is a handy-dandy little shell script. It takes all the plain files
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(not directories) in the current directory and changes their names to
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lower case. Very handy when you unzip a bunch of MS-DOS files.
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If a name change would result in overwriting an existing file the script
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asks you before doing the overwrite.
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<PRE>
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--------------------------- cut here -----------------------------------
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#!/bin/sh
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# lowerit
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# convert all file names in the current directory to lower case
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# only operates on plain files--does not change the name of directories
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# will ask for verification before overwriting an existing file
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for x in `ls`
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do
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if [ ! -f $x ]; then
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continue
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fi
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lc=`echo $x | tr '[A-Z]' '[a-z]'`
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if [ $lc != $x ]; then
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mv -i $x $lc
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fi
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done
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</PRE>
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="user"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="user">
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Removing Users
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</a></H3>
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<P>
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Date: 11 Nov 1996 18:54:02 GMT <BR>
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From: Geoff Short, <A HREF="mailto:grs100@york.ac.uk">grs100@york.ac.uk</A><BR>
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<P>
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To remove users do the following:
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<P>
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Simple setups:
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<ul>
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<li>Delete password entry for user from /etc/passwd
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<li>Remove user's files using rm -r /home/user
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<li>Reboot (if any processes still running)
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</ul>
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More complex setups:
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<ul>
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<li>http://kipper.york.ac.uk/rmuser.html
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</ul>
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Geoff
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<PRE>
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----------------------------------------------------------------------------
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Ever sit and watch ants? They're always busy with grs100@york.ac.uk
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something, never stop for a moment. I just geoff@kipper.york.ac.uk
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can't identify with that kind of work ethic. http://kipper.york.ac.uk/~geoff
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----------------------------------------------------------------------------
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</PRE>
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="pass"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="pass">Root and Passwords</a></H3>
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<P>
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Date: Fri, 1 Nov 1996 09:58:52 -0800 (PST)<BR>
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From: Steve Mann <A HREF="mailto:smann@ultrix.ramapo.edu">smann@ultrix.ramapo.edu</A><BR>
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Subject: Re: Root and passwords
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<P>
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If you have forgotten your root password:
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<ol>
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<li>Use a boot disk.
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<li>Login as root.
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<li>Mount the partition with your Linux.
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<li>Edit the second field, which is the encrypted password, of /etc/passwd
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to show nothing. It would look something like this:
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<PRE>
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root::0:0:root,,,:/:/bin/zsh
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</PRE>
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instead of something like this:
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<PRE>
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wimpy:GoqTFXl3f:0:0:Steve:/root:/bin/zsh
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</PRE>
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</ol>
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You should then be able to login as root with no password at all.
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<P>
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Steve
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<PRE>
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==================================================================
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/ Steve M Insignificant message goes here \
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| CCIS: 529-7500 x7922 \|||/ |
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| Home: 722-1632 0 * |
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| Beeper: 1-800-502-2775 or 201-909-1575 oo0 ^ 0oo |
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| Email: smann@ultrix.ramapo.edu ~~~~~~~~~ |
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| Ramapo College Apartments (Cypress Q): 934-9357
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\ This line left blank for no reason /
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=================================================================
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</PRE>
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="talk"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="talk">
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Talk Daemon and Dynamic Addresses
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</a></H3>
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<P>
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Date: 11 Nov 1996 16:33:02 GMT <BR>
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From: Adam Jenkins, <A HREF="mailto:ajenkins@kalgoorlie.cs.umass.edu">
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ajenkins@kalgoorlie.cs.umass.edu </A><BR>
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Organization: CMPSCI Department, UMass Amherst <BR>
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<P>
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Having problems sending a talk request to an IP-address other than your own?
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<P>
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The solution is to reset
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your host name to your new dynamic address. You need to figure out what dynamic
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address you've been assigned. Then you can use the "host" command to find the
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symbolic name for it, and then use the "hostname" command to reset your
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machine's hostname. Like this:
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<P>
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host 128.119.220.0a
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<P>
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Prints out a name. Use it in:
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<P>
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hostname name.domain.edu
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<P>
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That's it. You need to be root to run the "hostname" command with an argument. If
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you're using pppd to get your connection, you can put all of this into your
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/etc/ppp/ip-up script -- read the pppd man page for more info -- so that it will get
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done automatically when you log in.
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<P>
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The reason you need to do this is because when talk sends a talk request, it also
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sends along what it thinks is the return address so that the remote talk can respond.
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So if your local machine has a fake address, the remote talk will get that as the
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return address and you'll never see the response.
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<P>
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I also saw a patched version of talk on sunsite somewhere, where he made some hack to
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talk to get it to find your real address. But I like the "hostname" solution better
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because I've found at least one other program with the same problem, and the
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"hostname" solution fixes it too.
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<P> <hr> <P>
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<!--================================================================-->
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</td> </tr> </table>
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<a name="tar"><p></a>
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<table>
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<td><img src="../gx/blank.gif" width=50></td>
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<td>
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<H3><IMG ALIGN=BOTTOM ALT="" SRC="../gx/lil2cent.gif"><a name="tar">tar Tricks</a></H3>
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<P>
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Date: Tue, 12 Nov 1996 15:01:58 +0000 <BR>
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From: Dominic Binks <A HREF="mailto:dominic.binks@aethos.co.uk">dominic.binks@aethos.co.uk</A><BR>
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Organization: AEthos Communication Systems Ltd. <BR>
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<P>
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A couple of things that interested me about the article on tar. I'm
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sure that the idea is to introduce pipes, and some of the lesser known
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unix utilities (tr, cut), but
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<PRE>
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tar -tfvz file.tar.gz | tr -s ' ' | cut -d ' ' -f8 | less
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</PRE>
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can be written more concisely
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<PRE>
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tar tfz file.tar.gz | less
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</PRE>
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Also you can use wild cards so
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<PRE>
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tar tfz file.tar.gz *README*
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</PRE>
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will list all readmes in the file.
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<P>
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Finally two last pieces of useful Unix magic.
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<PRE>
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tar cfv - dir
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</PRE>
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|
will tar the directory dir and send the output to standard output. One
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|
piece of magic liked by Unix gurus is
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<PRE>
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|
tar cfv - dir | (cd dir2; tar xf -)
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|
</PRE>
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|
which copies one directory hierarchy to another location.
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|
<P>
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|
Another piece of tar that might be really useful is that taring up a dos
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|
file system and moving it somewhere else will preserve *everything*.
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|
This means you can move your main DOS partition around, something that
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|
is very difficult to do with DOS.
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|
<P>
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|
One final tip for all UNIX newbies: you got a file which unix will not
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|
allow you to delete.
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|
<PRE>
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|
rm -- 'file'
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|
</PRE>
|
|
will get rid of it. In general -- terminates argument processing so
|
|
that everything following is passed directly to the executable.
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|
<P>
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|
Have fun
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<P>
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|
Dominic Binks
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<P> <hr> <P>
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