Sunday, 19 May 2013

Linux Softwares


Linux Softwares


Software is what makes the system work. Without software, a computer system would be useless. We cover
important software issues here, and how small programs found on remote Web sites can solve most of your
problems.

Tip 1: Background image in X Window



By default, the background in X Window is a grey background. Some window managers have their own
options to set other backgrounds, and some don't.

A program you can use to set your background is a program that comes with most Linux distributions. It's
called XV, and you can specify which background image you want with this line:
xv -quit -root image.gif
This will set the background to be the image.gif file. You can add that line in your .xinitrc file, in your home
directory, so it is executed each time you launch X Window.


Tip 2: Customize Netscape Communicator



Netscape Communicator has one nice feature that few people use. When you download it, it has a Personal
Toolbar with buttons that most of us may not find really useful, so we either turn it off or don't look at it.
I found it to be a much more useful tool than the Bookmarks. What appears on that bar is simply what's
inside the Personal Folder inside your Bookmarks.
You can ceate folders in it for news sites, Linux sites, etc and move your bookmarks into them (with the Edit
Bookmarks option).
You then have your own personal portal in your browser:


Tip 3: POP3 in Pine



Many Linux users use Pine as their mail client. Lets see how you can use Pine both with local mail and with
POP3 mail, without using fetchmail or some other tool to get POP mail first.
First you will want to use multiple config files:
pine -p localmail
pine -p popserver1
pine -p popserver2
You need to configure Pine to use your POP3 server. In the program go to Setup, Config. You'll want to set
something like this in your inbox-path:
{pop.server.com/pop3/user=myid}INBOX
Now restart Pine and it will ask you for your password and connect to the remote server, and use it just like if
you were accessing local mail.

Tip 4: Multiple accounts in Pine



You can use multiple POP3, IMAP or other incoming mail accounts in the same config file by editing the line
"incoming-folders=" from .pinerc in your local home directory.
The syntax is:
incoming-folders= "Nick1" {pop1.domain.com/pop3/user=login}INBOX,
"Nick2" {pop2.somewhere.com/pop3/user=login}INBOX
This will create a new collection in Pine with these folders in it, plus the mail folder on the local system.


Tip 5: Running Java programs



Java is an interpreted language. Usualy Java is found on the Web, in small programs called applets. But many
Java applications exist. They are like applets, but require a Java Virtual Machine to run on your system.
Netscape Communicator and any Java-enabled browser can run Java applets, but what if you want to run Java
programs?
Java programs are files ending with .class and must be run in a JVM. The Java Development Kit comes with
a JVM. What you need is the Linux port of the JDK that you can find at http://www.blackdown.org. Once
installed, you can run any Java application using the line:
java Program
Where java is the JVM, from the JDK package, and Program is the class found inside the Program.class file.
Note that you do not have to specify the .class part of the file to run it.

Tip 6: Virtual hosts in Apache



Apache, the popular Web server for Linux and Unix, allows you to host virtual hostnames with multiple IP
addresses. You can set one IP to each hostname. But what if you want to host multiple hostnames on a single
IP? Apache allows you to do it.
The trick is a single command that goes in the httpd.conf configuration file:
NameVirtualHost 1.2.3.4
Replacing 1.2.3.4 with your real IP address, this will allow Apache to know on which IP it should serve the
virtual hostnames. Then you can add the virtual commands for every hostname you want to host:
<VirtualHost virtual.host.com>
ServerAdmin webmaster@virtual.host.com
DocumentRoot /home/httpd/virtual
ServerName virtual.host.com
</VirtualHost>
This will add virtual.host.com in your list of virtual hosts and serve the pages in /home/httpd/virtual. Of
course you need to have the actual virtual.host.com hostname pointing to that system.


Tip 7: Libc versus Glibc



A few years ago, every Linux system used the libc version 5.x library. The libc library is the main library that
all Unix C programs use. The functions they access are defined in that library.
Recently a new version of the library was introduced by the GNU project called GNU libc, or glibc, which is
also called libc 6. Some distributions and older systems won't have glibc, and they won't support glibc
binaries. This doesn't change anything for binaries you compile, but binaries you download that are linked to
the GNU libc will not work.
There are 2 ways to get them to work. The first is to upgrade. You can upgrade to a newer version that does
support glibc, or change your distribution to one that already has glibc as its main library. The other way is to
install glibc on your current system. This requires you to know what you are doing and to backup your
system first. See the GNU page at http://www.gnu.org page for more information on GNU products.


Tip 8: Aliases with Qmail



Qmail is a mail program that allows users to send and receive emails. It also has a lot of good features, one of
them being aliases. You can add aliases to users who do not have an account on the system. Here is how to do
it:
•??Create an account called "alias" if it doesn't exist, and go in its home directory.
•??Edit a file called .qmail-username where username is the alias you want to add.
•??Add the address in the file with a & in front of it.
Here is an example of a .qmail-username file:
&me@mydomain.com
&meagain@some.other.domain.net
This will forward any mail going to user "username" to the 2 listed email addresses.

Tip 9: Samba with Windows 98 or NT 4



Samba is a product allowing you to connect your Linux systems to Windows systems for file and printer
sharing. By default the SMB protocol used by Samba sends passwords in clear text. Windows 98 and NT use
encrypted passwords.
If you can't seem to connect from a Windows system on a Samba server, it might well be because the Samba
server doesn't know about the encrypted passwords. You need to read the documentation about encryption in
the Samba package. There is a utility to convert a Linux /etc/passwd file to encrypted mode so Samba can
support Windows encrypted passwords.
Note that Samba also works with Windows 3.1 and Windows 95, with no encryption.


Tip 10: KDE drag and drop icons



KDE is a window manager for the X Window system. It comes with a toolbar at the bottom of the screen and
default buttons. You can drag icons from your desktop to the toolbar. The problem is that there is no option to
add icons.
The trick is to drag a file on the toolbar and then edit it. Open KFM and drag the program you want on the
toolbar. You can then edit it and change the settings of the new icon in the toolbar:


Tip 11: Find files



Find is a very useful and powerful utility. It is often used by system administration and in shell scripts. Here
are 2 commands that might be useful:
find / -perm -4000 -print
This command will find every file on the system that is suid. This means that when you run it you will be
running it as an other user. For example, traceroute is a utility that needs to be run as root. To allow users to
run it, systems administrators will set it suid root so it will be run as root even if a user starts it. This can be
useful, but can also be a big security risk if the utility has a security hole in it.
Here is another interesting command:
find / -atime +10 -print
This command will find all the files accessed more than 10 days ago. Commands like this one can be useful
to find old files that need to be backuped or erased.


Tip 12: asm or linux include files not found



On older Linux systems, you may have some errors about include files not found in the asm/ or linux/
directory when you try to compile some programs. This means that the kernel source code was not installed.
Bot asm/ and linux/ directories are links to the kernel source code.
To install them on your system, you need to get the kernel source code. Then you need to link the directories:
ln -s /usr/src/linux/include/asm /usr/include/asm
ln -s /usr/src/linux/include/linux /usr/include/linux
This will link the 2 directories in the include tree allowing applications to find them.


Tip 13: ICQ on Linux



The original ICQ client does not currently run on Linux. Fortunately, there are clones that do run on Linux
and offer the ICQ service to users. A popular ICQ program is Licq available from http://licq.wibble.net.
Another popular one is Micq available at http://micq.chatzone.org. Other ICQ programs are also available for
Linux. This is licq:


Tip 14: Reading foreign documents



Linux comes with various freely available word processors and office suites. Unfortunately, Microsoft Office
doesn't come with a Linux native port. But you can still read and write Word and Excel files.
Word Perfect is a Corel word processor product that has a Linux port. The latest version is Word Perfect 8. It
is available freely for personal use on Linux, and will read and write Word files. It is available from
http://linux.corel.com. Another program is Star Office. This product from Star Division looks very much like
Microsoft Office and offers similar features. It will also read and write all kinds of file formats. Star Office is
available freely for personal use from http://www.stardivision.com:


Tip 15: Scanning with Linux



A number of scanning programs exist for Linux. A popular one currently is SANE which stands for "Scanner
Access Now Easy" and is available from http://www.mostang.com/sane. It is an application programming
interface that provides standardized access to scanners.
Several graphical frontends are also available from the SANE Web page.


Tip 16: Real audio and video



Real Networks has released their Real Player for Linux. Unfortunately, many users had problems setting it
up. When running an older kernel, you may need to disable the 16bits sound playback. When running the
Linux kernel 2.2 with Real Player 5.0, you may need to use a workaround to get the Real Player to work. The
workaround is available from the Web.
Real Networks provides the Real Player for Linux and for RedHat Linux. The RedHat Linux version comes
in the RPM format. Here it is:


Tip 17: Emulation



Linux is source compatible with Unix. This means that all of the Unix programs should work on Linux when
compiled correctly, with little or no change to the source. Unix does provide a wide variaty of software
programs, but some programs are only available on non-Unix systems.
A number of emulators are available on Linux. We'll see 4 of them:
•??One of them is called WINE and stands for WINE Is Not an Emulator. It used to stand for
Windows Emulator. WINE will run various Windows 16bits and 32bits applications. The
home page for WINE is at http://www.winehq.com.
•??To emulate DOS programs, a program called DOSemu exists. That program comes with an X
Window interface and a console interface. It will run most DOS programs. You may want to
run graphic-intensive programs like DOS games in the console interface of DOSemu. Like
WINE, DOSemu is a free product.
•??To emulate MacOS programs, a commercial program called Executor exists. It will run a
MacOS-like shell in X Window and will run various MacOS programs.
•??A new commercial program is now available for every OS. It is called VMware and will create
a virtual PC, allowing you to run nearly any operating system, including DOS, Windows NT
and FreeBSD. It is very stable and comes with a 30 day free license.


Tip 18: Shared library not found

Binaries need to load shared libraries at runtime. They are files on your system that provide functions to the
program. Sometimes the program will report that a shared library was not found, and it will abort.
To find which libraries a program needs, you can use the ldd program. It will list all those libraries and those
missing. If you know that a library is installed, maybe you need to add it to the current library path. The path
used to look for shared libraries is in /etc/ld.so.conf. You can modify that file and add any path you want,
then as root run the ldconfig program.


Tip 19: Hard to erase files



File names in Linux can have many letters and numbers in them. Usualy, names should not have spaces in
them, although Linux can deal with them. There are some characters that should not be used in files, like "/"
and "~".
Some programs unfortunately will create strange looking file names, often as temporary files. Using the rm
command, you should be able to remove them, but it may be hard when strange alphanumeric characters are
used. Here are a few ways you should try to get rid of a file with a strange name:
•??First you should try the following:
rm -f "file name"
•??If this doesn't work you should try the console program mc.
•??With graphical file managers, you should be able to pick an icon and remove it, regardless of
the file name.

Tip 20: Files permissions



When you try to run a file it may refuse to work with an error like "Permission denied" and when you try to
view another file it may also say that you don't have permission to view it. These all come down to file
permissions, a basic feature of Unix.
There are 3 types of permissions: read, write and execute. When you list files it will say which permission the
files have:
ls -l file.dat
-rw-r--r-- 1 root users 1656 Mar 22 00:27 file.dat
The first part of that line is the permissions. They are, in order, the user permissions, the group permissions
and others permissions, where r means read, w means write and x means execute. For this file, the user, root,
has read and write permission (rw-), the group, users, can only read the file (r--) and everyone else can also
only read the file (r--).
Other letters may appear. The first letter is - for a normal file, d for a directory and c or b for a device. In
place of x you may see a letter s. This means that when you start a program, it will run as its owner.

Tip 21: Changing file permissions



To change a file's permissions, you need to use a program called chmod. With that command you can change
one or multiple file permissions. Here are a few examples:
$ chmod 755 file
$ ls -l file
-rwxr-xr-x 1 root users 1656 Mar 22 00:27 file
$ chmod 700 file
$ ls -l file
-rwx------ 1 root users 1656 Mar 22 00:27 file
$ chmod 664 file
$ ls -l file
-rw-rw-r-- 1 root users 1656 Mar 22 00:27 file
The numbers are based on the 3 types of permissions. Read = 4, write = 2 and execute = 1. A permission of
755 means the user will have read, write and execute permissions (4 + 2 + 1 = 7), and everyone else will have
read and execute permissions (4 + 1 = 5).


Tip 22: An international background



To set a background in X Window, most of the time you will use XV or a similar program to set a static
image. But there is a program out there that allows you to put something useful on your background.
Xearth, available from http://www.cs.colorado.edu/~tuna/xearth/index.html, is a program that will display a
map of the world on your background, with some useful information. The main use is to display where the
sun currently lights the planet. It will also display the current time, and stars in the sky if you want to.
Several options exist. By default, Xearth will show a round planet, but you can make it display a rectangular
map:
xearth -proj merc
Other options are available, including mono display, the number of colors, and the running priority.


Tip 23: Powerful file transfer system



Downloading several directories from an FTP server, or mirroring a web site, can be hard to do using
traditional file transfer programs.
A program called wget is available from the GNU archive at ftp://ftp.gnu.org. This is a powerful program
allowing you to do advanced functions like fetching recursive directories and even retrieving full web sites.
A graphical frontend using the GTK library is available from
http://usuarios.meridian.es/frimost1/gwget/gwget.htm.


Tip 24: Editing in text editors


One common complaint among new Linux users is that vi or other text editors are too hard to use. That may
be true, but they aren't the only available editors.
Experts used to tell new users to learn ed or vi and that they would not regret it. It was true in the past, but it
is no longer necessary to learn hard to use editors to do powerful text editing.
Graphical editors most likely came with your distribution. You may not have installed them, but they are on
your CD-ROM. Some exemples are pico, a console full screen text editor, and emacs, which work on console
and X Window, and is a very powerful text editor.
Desktop interfaces such as GNOME an KDE each come with their own text editors too. You can even find
more editors on the Web.

Tip 25: Documentation and manual



Software under Linux rarely comes with printed documentation. Some do, like the GIMP and Blender, but
most only come with online documentation. This way, you can get the documentation at the same time that
you download the program.
There are 2 traditional ways to provide documentation under Unix and Linux:
The first is man pages. These are small files containing information about every command you have on your
system. For example, if you want to know what the command df does, simply type:
man df
The man system works with level of commands, from 1 to 8, plus other extensions. For full details about the
man program, simply see its manual page:
man man
The second way to provide help is with the info system. These are usually much bigger files (the libc info
files have more than 10,000 lines of text).
To access info files, simply type the info command. It is a bit harder to use, but you can get help by typing h

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