The Weekend Mechanic

Welcome to the June edition

Welcome back, this time to the June Edition of the Linux Weekend Mechanic.How have you all been?? I have been incrediably busy. You would not believe the amount of geology coursework that I have to do as part of my course. I can tell you one thing though....I hope that I never have to write about "the palaeographical environments that the wenlock limestone formed in, with relation to the fossil corals", ever again!!

The LWM mailbox

What follows, is any e-mails that I received, related to the previous Linux Weekend Mechanic. See what you think.....

From:    Thomas Nyman
To:      "Thomas Adam", <n6tadam@users.purbeck.dorset.sch.uk>
Sent:    Friday, May 04,2001 10:33 AM
Subject: Weekend mechanic

I like the "mechanic"
Two things that I would like to see explained are these.

1) If I install windows I may have a number of problems but never with my
monitor and graphical interface. Personally I have often experienced the
problem that I cannot get Xwindows to show on the screen monitor in a satisfactory
way, i.e its either way to big for my monitor or its way to small...I
have so far not found an easy to understand explanation on how to remedy such a
problem.

2) It would be "darn nifty" if you could put in a section on how to login via telnet
and run xwindows on another machine.

Anyway, thanks, and keep up the good work,

Thomas

From: nomi 
To: "Thomas Adam", <n6tadam@users.purbeck.dorset.sch.uk>
Subject: Linux Weekend Mechanic
Date: 12 May 2001 16:05

Hi, I read your article on LinuxGazette.  Could you cover how to setup
X, mainly the XF86Config file(s)?  I'm a console guy and know what I
need to know there, but when it comes to X (and editing it's
settings)..I'm totally lost.  Thanks.

Syed N. Ahmad

From: Don Reid 
To: <n6tadam@users.purbeck.dorset.sch.uk>
Subject: shell aliases
Date: 08 May 2001 21:21

Your article on "Customising the Shell Environment" has a lot
of good info for people new to the command line.

One point I would like to add is that you can get into a lot
of trouble by aliasing over existing commands (rather than making
up new names).  If you run a script that uses one of these commands,
your changes may alter the way it works.

My preference is to retrain my fingers to type a new command.

There are ways to restrict aliases to interactive shells, but
those don't work for sources scripts.


--
Don Reid

From: root 
To: <n6tadam@users.purbeck.dorset.sch.uk>
Subject: thank for the bash tip
Date: 10 May 2001 13:24

I tried the tip about the shortcut in .bashrc. At first it did not work;
meaning: I was recieving the no command found ect... So after a reboot,
it work perfectly and made some other shortcuts that worked at the first
time or trial.

I wonder what will be next? and I waiting to see it.

Thank you for your time

Sylvain.

From: Paul Rowland 
To: <n6tadam@users.purbeck.dorset.sch.uk>
Subject: weekend mech
Date: 02 May 2001 12:48

Dude,

Your comments are totally in geekdom. You rule!

Paul

From: Josef Moffett 
To: <n6tadam@users.purbeck.dorset.sch.uk>
Subject: Your Cron bits and bobs
Date: 08 May 2001 6:17

Hi there Thomas,

I've been using Linux now for about 3 years, and recently (about a year ago
now - time really flys when you're  having fun ;-) installed debian on an
old 486 at home to give me a masq box and firewall for my small home
network.

All my machines run linux at some point, but generally (mainly because I am
a flightsim maniac - fly II is out now, woo hoo) still am tied to windows. I
am dying for flight gear to come out a bit more stable so I can run it on
Linux!

Anyway, back the email (sorry about the ramble). I've been looking for more
info about Cron for ages now. I use the linux box as a local mailserver and
newserver (using leafnode). The pop3 server seems to work on its own -
although I do have a few quirks. Of course for this, I've got to get it
dialing in every now and then.

So far what I've done is to hijack (quite blatantly) the standard once a day
cron script (by the name, strangly enough of "standard" ;-) and tell it to
dialup using pon with a provider script with a very short timeout (30 secs).
In my ip-up script i then add fetchmail and fetchnews.

It works, but of course doesn't do it more than once a day, and reading
through man cron.d and the like, didn't really get me much further. I've
always got some wierd error. (I can't remember what it was, I think about
permissions - despite using it as root, but not serious).

Added to that, is the fact that it works (just less often than I'd like) and
the addage does say, "if it ain't broke...". Anyway, your article looks like
just the thing to get me to sort this out more professionally.

And then, perhaps I'd need to find a way to increase the "quiet hours" at
home so that I can find the time to work on the linux box (or anything else
in the computers!) without my 19month son helping my efforts by banging away
at the keys!

Cheers, and thanks again

JOE

Linux Installation: Xwindow and monitors

Thomas Nyman in his e-mail (see above), raised a good point about how installing your monitor does not always work, when using Xwindow. Indeed, I had not really given it much thought, as I had always fixed it, without really thinking what I was doing.

When I first installed Linux (all those years ago), I immediately booted into AnotherLevel (FVWM2), and realised that my screen resolution was set at 640x480, and that everytime I tried to open a window, I could not see enough of it to click to change any of the settings. What was going on??? I was sure that I had told it to use 800x600 screen resolution!! If you find that you have a similar problem, then I have a very quick fix.....

1. Change to a spare terminal, by pressing <Ctrl><Alt><Fx> ("Fx" being a function key). Now log in as root

2. Edit the file "/etc/XF86Config" using your favourite text editor.

3. Because XF86Config varies with different Linux distributions, I cannot say specifically where the section is, but you want to find the section labelled Screen which should look something like this....

Section "Screen"
Driver  	"SVGA"
SubSection "Display"
Depth  	8
Modes  	"800x600"  "640x480"
EndSubSection

SubSection "Display"
Depth  	16
Modes  	"800x600"  "640x480"
  EndSubSection
  SubSection "Display"
    Depth  	24
    Modes  	"800x600"  "640x480"
  EndSubSection
  SubSection "Display"
    Depth  	32
    Modes  	"800x600"  "640x480"
  EndSubSection
  Monitor  	"Primary-Monitor"
  Device  	"Primary-Card"
  DefaultColorDepth  	8
EndSection

4. Now what you have to do, is to change the resolution for each colour depth that you will be using. To do this, you must edit the values next to "Modes". The syntax for this, is that the first value you come to is the one that is activated first, and then the second is a backup if the first value failed and so on.

To tell X that you want to use a certain colour depth, you must also edit the value next to "DefaultColorDepth" to be whatever depth that you want. Note: that you can only specify one default colour depth!!

So, if you will be running in 16bit mode with 800x600 display, then you would set the following, making sure that you specify the next resolution as a backup.

 Modes  	"800x600"  "640x480"

And then, if you have not done so already, change the value of "DefaultColorDepth" to be 16

And that is all there is to it. Save the file and then boot up your X display.

I know that there are programs which can do this editing for you such as "Xconfigurator", but I find that editing the file myself is much quicker!!

Setting up and customising Xwindow

This article may be of some use to those people who prefer the command line, but would like to use X, but don't know how to go about it.It may also be of use to those who are interested in getting X to work in a satisfactory manor. Now, I believe that this topic has been covered before in an early issue of the Linux Gazette, but as I was asked directly, I thought I would write the article anyway!!

Firstly, you must decide how you are going to run your X display. There are two ways of doing this, either by entering a different run-level, which will in turn run an X login client such as XDM, GDM, or KDM, or by typing in the command startx & at the console, after you have logged in.

The advantages of using the first method is that if you know that you will nearly always be using Xwindows then you won't have to worry about starting it yourself.

KDM has a nice feature that allows you to select a different Window Manager before you logon, which I have found quite useful. The configuration for this can be done from KDE itself, using the program "kcontrol". By clicking "Applications --> login". A screenshot of how to configure KDM can be seen below.

The other alternative that I mentioned was to use XDM. This is the login client that I use, as it is simple!! This one takes a little more configuration that KDM but it is the one that I like to use.

The files

Here are a list of files that we shall be using, and they are all found in the directory: "/etc/X11/xdm". The files we shall be concentrating on, are the following:

Customisation

I shall take each file in turn, explain that files role, and tell you the best way to customise it....

This file allows you to customise the look and feel of the main login window. You can also set and disable certain keystrokes. This file is probably the most important to customise.

While it may not be necessary for you to customise this file, I shall point out things that you can do, if you feel the need. I shall not be covering this file line by line, but most of the information in this file is quite self explanitory.

1. To change the text at the top of the login box, edit the value thus:

xlogin*greeting:	Welcome to this console

I have changed the "Welcome to this console" to "Welcome to CLIENTHOST". This is so that I know, on my home network, which terminal I am using. The "CLIENTHOST" is actually a variable, which holds the first part of your hostname. Thus, in my case it is Grangedairy, but if you have not changed your hostname since you installed Linux, then most likely, "CLIENTHOST" will return LocalHost

Just as an aside, if you do want to change your hostname, edit the values stored in the "/etc/hostname", and in a file "/etc/sysconfig/network", if the latter exists. Note, for the changes to take effect, you will have to switch to run-level 6 (init 6)

2. You can also change the colour of this greeting, to be whatever you like. Find the following:

xlogin*greetColor:		CadetBlue

I have changed the "CadetBlue" value to something a little more vitalising....guess what it is?? No? It's "Yellow", and rather surprisingly, it looks good too.

3. You can also change the width of various frames of the login window too:

xlogin*borderWidth:		2
xlogin*frameWidth:		0
xlogin*innerFramesWidth:	1

The first , sets the overall border commandwidth of the login screen. Experiment to see what a value looks like. I find that 2 looks ok, on both my desktop and laptop machines.

The second command, sets the frame width of the border. I tend to leave it at 0

The third command, set the inner frame width for each of the input fields in the main login window, namely "Login" and "Password". When I edited this value, I hated the outcome, as each of the boxes looked "embossed".

You can set things like the background colour of the main screen, and change the colour of the error message "Login Incorrect":

xlogin*failColor:		red
*Foreground:			black
*Background:			#c0c0c0

Thus, the first command is very self explanitory. It should also be said, that when changing values of this type, one can either specify the name of the file, or put the #RRGGBB format aswell.

The second and third commands, sets the foreground colour and background colour respectively.

Thats it for this file. I am sorry if all of this seems rushed, but the majority of the file is fairly straightforward. I just thought that I would highlight some points of interest.

Xservers

There really isn't much to say about this file, other than this file allows you to change virtual consoles. Although I would only advise changing these settings if you know that the VT you are changing to does not have mingetty running on it. I have had some interesting problems with this before!! If you are uncertain, consult the settings in "/etc/inittab"

:0 local /usr/X11R6/bin/X :0 vt07

So, to customise this value, change the number(s) after "vt", to start X on the virtual terminal of your choice. It is also worth noting that you can also specify the colour depth to use, if you are using one other than that set in the "/etc/XF86Config" file. To do this, append the following after the "vt07" bit to look like this....

:0 local /usr/X11R6/bin/X :0 vt07 -bpp 16

[I have xdm running two xservers, one on vt9 and the other on vt10. The first one is mine. I chose vt9 because F9 the first key in the third group of function keys. vt10 is for my roomates, so they can do their thang without disturbing my idle session. My /etc/X11/xdm/Xservers (on Debian) looks like this:

:0 local /usr/bin/X11/X :0 vt9  -bpp 24 -deferglyphs 16 dpms
:1 local /usr/bin/X11/X :1 vt10 -bpp 24 -deferglyphs 16 dpms                    

-Mike.]

xdm-config

This file sets the various configurations of XDM, by invoking various files. I have never had to customise this file, so I doubt if you will either!!

window-managers

This file holds a list of window managers that X will use. Note that you can specify as many as you like, one after the other, line-by-line, but only the top one will get executed. And, if it cannot find it, then it executes the second one down, and so on. Thus my configuration is thus:

/usr/bin/X11/AnotherLevel
/usr/bin/X11/twm
#file below symlinked from "/usr/openwin/bin/openwin"
/usr/bin/X11/openwin

Closing Time

Well kind people, that concludes this months Linux Weekend Mechanic. Thanks once again to everyone who took the time to send me an e-mail, praising me, pointing out my areas of weakness, and giving article ideas. I am currently working through all your article suggestions, so please bear with me. Any more input that people can provide, is always welcome!! Keep those e-mails flooding in please!!

Anyway, I must be going. I have still got to work on my chemistry (revising the reaction conditions necessary to reduce a carboxylic acid to an alcohol using Lithiumaluminiumhydride, I think). I have then got to go and teach piano, and do some much needed Geography work. It is all go!!

In the meantime (and as like last weeks' ending)Happy Linuxing....

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