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# Talkback

### Talkback:143/lg_mail.html

[ In reference to "Mailbag" in LG#143 ]

Etienne Lorrain [etienne_lorrain at yahoo.fr]

Wed, 3 Oct 2007 15:13:03 +0200 (CEST)

Clock problem

    >Hi , my name is Jimmy,can anyone help me fix the time on my PC.  I
    >change the Battery so many time ,I mean the new CMOS Battery ,but my
    >time is still not read correct

Check the board jumper which reset the CMOS configuration and your motherboard documentation - this jumper shall not be let in the "reset" position while operating the computer...

Just a guess.

### Talkback:143/sephton.html

[ In reference to "A Question Of Rounding" in LG#143 ]

Mauro Orlandini - IASF/Bologna [orlandini at iasfbo.inaf.it]

Tue, 2 Oct 2007 09:53:23 +0200 (CEST)

Talking about rounding, I almost went crazy to find out why a perl program I was writing did not give the right result. Here is the code:

    #!/usr/bin/perl
    #
    $f = 4.95;
    $F = (4.8+5.1)/2;
    $F_spr = sprintf("%.10f", (4.8+5.1)/2);

    printf "     f: %32.30f\n", $f;
    printf "     F: %32.30f\n", $F;
    printf " F_spr: %32.30f\n", $F_spr;

    if ($f == $F) { print "\n f equals F!\n\n"; }

The test fails even if $f and $F are the same! I solved by using $F_spr instead of $F, but it took me a day to find it out... 8-(

Ciao, Mauro

    --
      _^_                                                                    _^_
    ( _ )------------------------------------------------------------------( _ )
      | / | Mauro Orlandini          Email: orlandini at iasfbo.inaf.it           | \ |
      | / | INAF/IASF Bologna        Voice: +39-051-639-8667                   | \ |
      | / | Via Gobetti 101          Fax:   +39-051-639-8723                   | \ |
      | / | 40129 Bologna - Italy    WWW:   http://www.iasfbo.inaf.it/~mauro/  | \ |
      | / |--------------------------------------------------------------------| \ |
      | / | Today's quote:                                                     | \ |

[ Thread continues here (6 messages/16.07kB) ]

### Talkback: 143/anonymous.html

[ In reference to "Linux Console Scrollback" in LG#143 ]

Andre Ferreira [andre.ferreira at safebootbrasil.com.br]

Thu, 18 Oct 2007 10:20:23 -0300

Hello,

I have a suggestion for the article about the Linux Console Scrollback that appears in Linux Gazette #143 (October 2007).

He talks about the console scoll back function is not enough to see the kernel messages, also he talks about see the message log that don't have everything.

My suggestion is to mention the "kernel ring buffer" that can be accessed and manipulated using the command "dmesg".

Of course change the size of the scroll back buffer in console has other uses than to see the output of the kernel boot, but as he gives this as an example I think is useful to talk about the kernel ring buffer.

Best regards,

Andre

### Talkback: issue45/lg_tips45.html

[ In reference to "/lg_tips45.html" in LG#issue45 ]

Gary Dale [garydale at torfree.net]

Wed, 17 Oct 2007 19:33:16 -0400

While the coverage of this topic was generally thorough, there was one important point that was missed. If you want to use tar to directly split archives, you cannot use compression. If you want a compressed archive, you must compress it first then use split to break it into appropriate chunks.

However, if you do things this way, you must be aware that each chunk must be good for you to be able to rejoin them later. For example, if you were to split an archive into IG segments to back up to a UDF filesystem (until recent kernels there was a 1G limit on UDF files) such as a DVD-RAM, you must verify the copies to ensure you will be able to restore the original archive later. If one of the segments develops a bad sector, you may lose the entire archive.

### Talkback: 135/misc/lg/diagnosing_sata_problems.html

[ In reference to "Linux Console Scrollback" in LG#135 ]

Neil Youngman [ny at youngman.org.uk]

Thu, 25 Oct 2007 22:02:09 +0100

On Thursday 25 October 2007 20:18, you wrote:

    > Hi!
    > I read your post in
    > http://linuxgazette.net/135/misc/lg/diagnosing_sata_problems.html
    > Did you get your sata drive work?
    > I've got these kind of problems:
    > http://ubuntuforums.org/showthread.php?t=591288
    > Can you give any advices?
    >
    > -Juho from Finland

I solved my problems by replacing the SATA card. I'm afraid I can't offer much advice. If it was working before you upgraded and you haven't touched the hardware then it sounds like software. I'd try a few different live CDs (Knoppix, Mint, etc), see which ones work and look at whether there are obvious differences, such as modules loaded. That might offer some clues.

I've Cced the Answer Gang to see if they can offer any more useful advice.

Neil

### Talkback: 108/bilbrey.html

[ In reference to "Using a Non-Default GUI (in RHEL and kin) " in LG#108 ]

Brian Bilbrey [bilbrey at orbdesigns.com]

Wed, 31 Oct 2007 18:29:19 -0400

On Wed, Oct 31, 2007 at 12:15:46PM -0700, nishith datta wrote:

    >    hi brian,
    >    Sorry if I am bothering you with this email.
    >    This is in connection with your article about winmans in linuxGazette. It
    >    was very informative and good. I was struggling with installing fluxbox on
    >    RHEL 4.0 and I finally could do it with help of your article.
    >    Just that I have not understood what is the purpose of  the following
    >    files /etc/X11/gdm/Sessions/fluxbox and the
    >    /etc/X11/dm/Sessions/fluxbox.desktop.
    >
    >    Both have a exec command and I have entered the fluxbox binary only in the
    >    fluxbox.desktop file . It is working fine . What is the fluxbox file in
    >    gdm/Sessions dir for ?
    >    my files look like this :-
    >       /etc/X11/gdm/Sessions/fluxbox file
    >        #!/bin/bash
    >        exec /etc/X11/xdm/Xsession FluxBox
    >
    >        /etc/X11/dm/Sessions/fluxbox.desktop file
    >        [Desktop Entry]
    >        Encoding=UTF-8
    >        Name=FluxBox
    >        Comment=This session logs you into fluxbox
    >        Exec=/opt/fluxbox-1.0.0/src/fluxbox
    >        Icon=
    >        Type=Application
    >    I hate to bother you . Hope it is alright and you will help me out in
    >    understanding things better.

No problem, Nishith. You're referring to this article, I think:

http://linuxgazette.net/108/bilbrey.html

I would hazard to guess that /etc/X11/dm is the default display manager directory, where by default I mean "the place where Red Hat expects to find display manager session stuff". Then there's directories for the assorted actual display managers: xdm, kdm, gdm. That's for stock X, KDE, and Gnome, respectively. But in each of those login manager screens, you can select which window manager you want to use for that (and optionally future) X sessions. So in each display manager configuration directory, there are session files designed to work with that particular display manager, for each installed Window Manager. So, for instance, if you installed RHEL4 in kitchen sink mode, with both KDE and Gnome goo, then you're likely to find these:

/etc/X11/ dm xdm gdm kdm

Then, when you install a non-stock RPM of, say, fluxbox, you'll likely find separate files for that window manager to define a session under each of those DMs. That they're different (which seems to be your confusion) is a function of the fact that each is a configuration file for a different display manager.

But all of the others eventually refer back to files in /etc/X11/dm/Sessions for the setup and startup of the window manager. In one Red Hat box I can touch, I find /etc/X11/gdm/Sessions/GNOME. That invokes /etc/X11/xdm/Xsession with an argument of "gnome". Looking at Xsession, I see that ... it leads elsewhere entirely: /usr/share/switchdesk.

[ ... ]

[ Thread continues here (1 message/4.29kB) ]

### Talkback: 141/misc/lg/backup_software_strategies.html

[ In reference to "Linux Console Scrollback" in LG#141 ]

Kapil Hari Paranjape [kapil at imsc.res.in]

Mon, 22 Oct 2007 11:05:33 +0530

Hello,

There was a discussion a while ago about Backup Strategies.

The enclosed URL points to some pre-strategic thoughts on Backup. I have not yet used this thinking to formulate a proper Backup plan that is consistent with it.

http://www.imsc.res.in/IMScWiki/WhatIsBackup

I have not yet submitted it as an article for LG since the actual strategy is missing --- what good is theory without a practical formula?!

Regards,

Kapil. --

### "A Question Of Rounding" in issue #143

Paul Sephton [paul at inet.co.za]

Sat, 06 Oct 2007 19:53:57 +0200

Hello, all

In order to clarify a few points, set some issues to rest, and update the listing of the source code that appeared in "A Question Of Rounding", the following may be of interest.

First of all, I have to state unequivocally that there is no bug. There never was a bug. The printf() family of functions completely follow the letter of both the C99 and IEEE specifications (at least for GLibC). The matter has been completely explored and put to rest.

The issues brought to light in the article are, however very pertinent to those of us who make a living producing code. The listing below addresses some of the real life issues some of us face when having to deal with floating point arithmetic.

Please refer to the discussion which follows for an explanation as to why printf() behaves the way it does, and what this code does to address some of the problems I highlighted in my article. The discussion is also a summary of some of the many points raised in the bug report discussion, and the information provided to me during that process by a few very smart people.

[ ... ]

[ Thread continues here (1 message/11.43kB) ]

Talkback: Discuss this article with The Answer Gang

Copyright © 2007, . Released under the Open Publication License unless otherwise noted in the body of the article. Linux Gazette is not produced, sponsored, or endorsed by its prior host, SSC, Inc.

Published in Issue 144 of Linux Gazette, November 2007

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