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RedHat Linux Unleashed

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Tux the Pengin

OK, here's a freebie: A simulation of the old text-based Star Trek game we used to play on HP 2100's using a Teletype ASR-33 as a console: StarTrek Game

Neat Linux Features Often Overlooked

There are various neat things to install that can dress up your Linux X sessions, and that can be useful and informative about your operating environment. I will document installation and setup info for some of them here, as I get them running on my system.

General instructions:

To install or perform some of these, you need to be "super-user" (root, jedi, whatever...); that's why I show the "#" prompt in the instructions.

If you are logged in as a user ("$" prompt), type su and then enter your root password at the prompt.

To download files or screenshots on this page, shift-click the links.

The Stuff:

Neat little Linux commands...

If you just use a point-n-click GUI all the time, it is easy to forget the neat little commands built into Linux that hackers have added to make programing life easier over the years. Like a calendar - or a floating digital clock! (these are in RedHat, may not be present in your distribution)

  1. The Calendar:
    cal >> this month's calendar prints in your terminal.
    cal -3 >> 3-month calendar centered on this month.
    cal -y >> calendar of the whole (current) year
    cal 2005 >> calendar of the year 2005
    cal 2003 | pr -o 5 | lpr >> prints a calendar centered on paper
    cal | xmessage -font 7x14 -file "-" & >> floating calendar window!
  2. X-Stickies:
    See that last one under "The Calendar"? You can use xmessage to put up temporary little notes to yourself, like PostIt notes, only from the commandline:
    xmessage "Your message here" &
    (Note: You can hit [enter] to format new lines until closing the message with double-quotes and the "&"-sign) Do not forget the "&"-sign; that prevents locking up your commandline. Unlike PostIt notes or knotes, these messages will be lost when you log out of the session.
  3. The Floating Clock:
    xclock -digital -bg black -fg green -update 1 &
  4. Getting lots of "404" errors for "oldimage.gif" in your site stats? Use grep to find the offending pages:
    grep -R "oldimage.gif" /var/www/html
  5. Just FTP'd a directory full of subdirectories that got their permissions rearranged? Use find to recursively change permissions on just the subdirectories, not the files:
    cd uploaded_directory
    find ./ -type d -exec chmod 755 {} ";"
  6. Got some text lines you need sorted alphabetically? Use Linux' "sort" comand:
    echo "(paste text to sort here)" > sortfile
    sort -o sorted sortfile
    The sorted text is now in the file "sorted".
  7. Want to know the ASCII code for any letter in octal, hex or decimal? It's at your fingertips -- just type man ascii on the commandline!

For full details on all the options to these little helpers, see your Linux "man" pages.

Creating favicons

This comes under the category of "Web Design": Let's dress up the new Web page with one of those little icons that sit beside the link in your bookmarks lists (favorites for you IE users).

  1. First, use the Gimp to create a 16 by 16-pixel image and save it as a .png image.
  2. Now download "png2ico" from http://www.winterdrache.de/freeware/png2ico/index.html and follow the instructions for compiling it in the README files.
  3. Use the utility to convert the png file with:
    png2ico favicon.ico your16x16.png
  4. Move the .ico file to your page's images/ directory, and add this line to the <head> of your page:
    <link rel="shortcut icon" href="images/favicon.ico">

Change Gnome icon text-color

When you use a dark background image for wallpaper or a dark color on your Gnome desktop, the normally-black icon labels can be difficult or impossible to read in the nice-looking "shaped-text" icon mode.

  1. Edit or create a ".gtkrc" file in your home directory.
  2. If the file exists, add a line to the bottom:
    include "/home/youruserdir/.gtkrc.mine"
    If it does not exist, create it with that line in it.
  3. Now create the ".gtkrc.mine" file:
    style "gnome-desktop-icon" {
    fg[NORMAL] = { 0.85, 0.85, 0.85 }
    bg[NORMAL] = { 0.0, 0.0, 0.0 }
    }
    widget_class "*DesktopIcon*" style "gnome-desktop-icon"
  4. The numbers can range from 0.0(black) to 1.0(white), and represent the RGB triplet defining the color of the icon text.

Reading a KODAK memory card

  1. As root, create a mount point:
    # mkdir /mnt/mem
  2. Insert the Kodak PCMCIA card and inspect /var/log/messages to see what device the card is identified as:
    # tail /var/log/messages.
    It should show up as a hard drive, like "hde:hde1".
  3. Now just mount the card as if it was a drive:
    # mount -t auto /dev/hde1 /mnt/mem
  4. You should then be able to see files on the card:
    # ls /mnt/mem

Hard disk speed-up

  1. First, test the current speed:
    # /sbin/hdparm -t /dev/hda
    A test is made and the rate in MB/sec tells the speed.
  2. Now determine your current settings:
    # /sbin/hdparm -c -d -m /dev/hda
    (Read up on hdparm - "# man hdparm")
  3. It is our experience that the -m option does not make much difference, and sometimes slows things down.
    This will usually boost speed:
    # /sbin/hdparm -c1 -d1 -k /dev/hda
    (-c1 = 32 bit I/O, -d1 = DMA on, -k = keep settings)
  4. If this works for you (makes a speed increase) just add that line to the end of your /etc/rc.d/rc.local file to activate it at startup.

ETerm

  1. Change to your home directory, if you are not already there:
    # cd
  2. Get the latest version source file here: http://www.eterm.org
  3. Unpack it:
    # tar -xzf Eterm*.gz
  4. Change to the unpacked directory:
    # cd Eterm-0.8.9
  5. Type:
    # ./ configure
    # make
    # make install
  6. The binary is installed in /usr/bin
  7. To open an Eterm in shaded transparency mode, type:
    # Eterm --trans --shade 30%
  8. For other options, see the man page for Eterm.
  9. Clean up your /home/root directory while still as root; The tar file and temporary Eterm-0.8.9 directory may be deleted.

Root-Tail

  1. Change to your /home/root directory, if you are not already there:
    # cd
  2. Get the source file here: root-tail-0.0.4b.tar.gz
  3. Unpack it:
    Type:# tar -xzf root-t*.gz.
  4. Type: # cd rt-0.0.4B
  5. Compile:
    # xmkmf -a
    # make
  6. Install:
    # cp rt /usr/X11R6/bin
    # cp rt.1 /usr/man/man1
  7. To invoke root-tail from the command line, type:
    # rt -g 80x12+50+10 /var/log/messages,green &
    This puts an 80-column, 12-line display 50 pixels to the right and 10 pixels down from the upper left corner. The file displayed is /ver/log/messages, and the type appears in green.
  8. For an explanation of the options, see the man page for rt.
  9. Clean up your /home/root directory while still root user; the tar file and temporary rt-0.0.4B directory may be deleted.

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