PAM (actually Linux-PAM, or Linux Pluggable Authentication Modules) allows a system administrator to determine how applications use authentication to verify the identity of a user. PAM provides shared libraries of modules (located in /lib/security) that, when called by an application, authenticate a user. The term “Pluggable” in PAM’s name refers to the ease with which you can add and remove modules from the authentication stack. The configuration files kept in the /etc/pam.d directory determine the method of authentication and contain a list (i.e., stack) of calls to the modules. PAM may also use other files, such as /etc/passwd, when necessary.
Instead of building the authentication code into each application, PAM provides shared libraries that keep the authentication code separate from the application code. The techniques of authenticating users stay the same from application to application. In this way, PAM enables a system administrator to change the authentication mechanism for a given application without ever touching the application.
PAM provides authentication for a variety of system-entry services (login, ftp, and so on). You can take advantage of PAM’s ability to stack authentication modules to integrate system-entry services with different authentication mechanisms, such as RSA, DCE, Kerberos, and smartcards.
From login through using su to shutting the system down, whenever you are asked for a password (or not asked for a password because the system trusts that you are who you say you are), PAM makes it possible for the system administrator to configure the authentication process. It also makes the configuration process essentially the same for all applications that use PAM for authentication.
The configuration files stored in /etc/pam.d describe the authentication procedure for each application. These files usually have names that are the same as or similar to the names of the applications that they authenticate for. For example, authentication for the login utility is configured in /etc/pam.d/login. The name of the file is the name of the PAM service2 that the file configures. Occasionally one file may serve two programs. PAM accepts only lowercase letters in the names of files in the /etc/pam.d directory.
PAM warns you about errors it encounters, logging them to the /var/log/messages or /var/log/secure files. Review these files if you are trying to figure out why a changed PAM file is not working properly. To prevent a malicious user from seeing information about PAM unnecessarily, PAM sends error messages to a file rather than to the screen.
Caution: Do not lock yourself out of the system
Editing PAM configuration files correctly takes care and attention. It is all too easy to lock yourself out of the computer with a single mistake. To avoid this problem, always keep backup copies of the PAM configuration files you edit, test every change thoroughly, and make sure you can still log in once the change is installed. Keep a Superuser session open until you have finished testing. When a change fails and you cannot log in, use the Superuser session to replace the newly edited files with their backup copies.
Source of Information : Prentice Hall A Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Showing posts with label Red Hat Linux. Show all posts
Showing posts with label Red Hat Linux. Show all posts
Sunday, December 12, 2010
Thursday, June 17, 2010
Controlling Windows : The Window Manager
A window manager—the program that controls the look and feel of the basic GUI—runs under a desktop manager (such as GNOME or KDE) and controls all aspects of the windows in the X Window System environment. The window manager defines the appearance of the windows on the desktop and controls how you operate and position them: open, close, move, resize, minimize, and so on. It may also handle some session management functions, such as how a session is paused, resumed, restarted, or ended.
Window decorations. A window manager controls window decorations—that is, the titlebar and border of a window. Aside from the aesthetic aspects of changing window decorations, you can alter their functionality by modifying the number and placement of buttons on the titlebar.
The window manager takes care of window manipulation so client programs do not need to do so. This setup is very different from that of many other operating systems, and the way that GNOME deals with window managers is different from how other desktop environments work. Window managers do more than simply manage windows—they provide a useful, good-looking, graphical shell to work from. Their open design allows users to define their own policies, down to the fine details.
Theoretically GNOME is not dependent on any particular window manager and can work with any of several window managers. Because of their flexibility, you would not see major parts of the desktop environment change if you were to switch from one window manager to another. A desktop manager collaborates with the window manager to make your work environment intuitive and easy to use. Although the desktop manager does not control window placement, it does get information from the window manager about window placement.
Fedora/RHEL Window Managers
Metacity and Compiz—the default window managers for GNOME—provide window management and start many components through GNOME panel objects. They also communicate with and facilitate access to other components in the environment. The Desktop Effects window allows you to switch between Metacity and Compiz.
Using the standard X libraries, programmers have created other window managers, including blackbox, fluxbox, and WindowMaker. You can use yum to install any of these packages.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Window decorations. A window manager controls window decorations—that is, the titlebar and border of a window. Aside from the aesthetic aspects of changing window decorations, you can alter their functionality by modifying the number and placement of buttons on the titlebar.
The window manager takes care of window manipulation so client programs do not need to do so. This setup is very different from that of many other operating systems, and the way that GNOME deals with window managers is different from how other desktop environments work. Window managers do more than simply manage windows—they provide a useful, good-looking, graphical shell to work from. Their open design allows users to define their own policies, down to the fine details.
Theoretically GNOME is not dependent on any particular window manager and can work with any of several window managers. Because of their flexibility, you would not see major parts of the desktop environment change if you were to switch from one window manager to another. A desktop manager collaborates with the window manager to make your work environment intuitive and easy to use. Although the desktop manager does not control window placement, it does get information from the window manager about window placement.
Fedora/RHEL Window Managers
Metacity and Compiz—the default window managers for GNOME—provide window management and start many components through GNOME panel objects. They also communicate with and facilitate access to other components in the environment. The Desktop Effects window allows you to switch between Metacity and Compiz.
Using the standard X libraries, programmers have created other window managers, including blackbox, fluxbox, and WindowMaker. You can use yum to install any of these packages.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Tuesday, June 15, 2010
Controlling Windows : Changing the Resolution of the Display
The X server starts at a specific display resolution and color depth. Although you can change the color depth only when you start an X server, you can change the resolution while the X server is running. The number of resolutions available depends both on the display hardware and on the configuration of the X server. Many users prefer to do most of their work at a higher resolution but might want to switch to a lower resolution for some tasks, such as playing games. You can switch between display resolutions by pressing either CONTROL-ALT-KEYPAD-+ or CONTROL-ALT-KEYPAD- –, using the + and – on the keyboard’s numeric keypad. You can also use the Monitor Resolution Settings window (Main menu: System -> Preferences -> Display) to change the resolution of the display.
Changing to a lower resolution has the effect of zooming in on the display; as a result, you may no longer be able to view the entire workspace at once. You can scroll the display by pushing the mouse pointer against the edge of the screen.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Changing to a lower resolution has the effect of zooming in on the display; as a result, you may no longer be able to view the entire workspace at once. You can scroll the display by pushing the mouse pointer against the edge of the screen.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Sunday, June 13, 2010
Controlling Windows : Changing the Input Focus
When you type on the keyboard, the window manager directs the characters you type somewhere, usually to a window. The active window is the window accepting input from the keyboard; it is said to have the input focus. Depending on how you set up your account, you can use the mouse in one of three ways to change the input focus:
• Click-to-focus (explicit focus)—Gives the input focus to a window when you click the window. That window continues to accept input from the keyboard regardless of the location of the mouse pointer. The window loses the focus when you click another window. Although clicking the middle or right mouse button also activates a window, use only the left mouse button for this purpose; other buttons may have unexpected effects when you use them to activate a window.
• Focus-follows-mouse (sloppy focus, enter-only, or focus-under-mouse)— Gives the input focus to a window when you move the mouse pointer onto the window. That window maintains the input focus until you move the mouse pointer onto another window, at which point the new window gets the focus. When you move the mouse pointer off a window and onto the root window, the window that had the input focus does not lose it.
• Focus-strictly-under-mouse (enter-exit focus)—Gives the input focus to a window when you move the mouse pointer onto the window. That window maintains the input focus until you move the mouse pointer off the window, at which point no window has the focus. When you move the mouse pointer off a window and onto the root window, the window that had the input focus loses it, and input from the keyboard is lost.
You can use the Window Preferences window to change the focus policy. Under Fedora, you must install the control-center-extra package before you can display this window. To display this window, select Main menu: System -> Preferences -> Windows or give the command gnome-window-properties from a terminal emulator or Run Application window (ALT-F2). Put a tick in the check box next to Select windows when the mouse moves over them to select the focusfollows- mouse policy. When there is no tick in this check box, click-to-focus is in effect. Click Close. Focus-strictly-under-mouse is not available from this window.
To determine which window has the input focus, compare the window borders. The border color of the active window is different from the others or, on a monochrome display, is darker. Another indication that a window is active is that the keyboard cursor is a solid rectangle; in windows that are not active, the cursor is an outline of a rectangle.
Use the following tests to determine which keyboard focus method you are using. If you position the mouse pointer in a window and that window does not get the input focus, your window manager is configured to use the click-to-focus method. If the border of the window changes, you are using the focus-follows-mouse or focusstrictly-under-mouse method. To determine which of the latter methods you are using, start typing something, with the mouse pointer positioned on the active window. Then move the mouse pointer over the root window and continue typing. If characters continue to appear within the window, you are using focus-followsmouse; otherwise, you are using focus-strictly-under-mouse.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
• Click-to-focus (explicit focus)—Gives the input focus to a window when you click the window. That window continues to accept input from the keyboard regardless of the location of the mouse pointer. The window loses the focus when you click another window. Although clicking the middle or right mouse button also activates a window, use only the left mouse button for this purpose; other buttons may have unexpected effects when you use them to activate a window.
• Focus-follows-mouse (sloppy focus, enter-only, or focus-under-mouse)— Gives the input focus to a window when you move the mouse pointer onto the window. That window maintains the input focus until you move the mouse pointer onto another window, at which point the new window gets the focus. When you move the mouse pointer off a window and onto the root window, the window that had the input focus does not lose it.
• Focus-strictly-under-mouse (enter-exit focus)—Gives the input focus to a window when you move the mouse pointer onto the window. That window maintains the input focus until you move the mouse pointer off the window, at which point no window has the focus. When you move the mouse pointer off a window and onto the root window, the window that had the input focus loses it, and input from the keyboard is lost.
You can use the Window Preferences window to change the focus policy. Under Fedora, you must install the control-center-extra package before you can display this window. To display this window, select Main menu: System -> Preferences -> Windows or give the command gnome-window-properties from a terminal emulator or Run Application window (ALT-F2). Put a tick in the check box next to Select windows when the mouse moves over them to select the focusfollows- mouse policy. When there is no tick in this check box, click-to-focus is in effect. Click Close. Focus-strictly-under-mouse is not available from this window.
To determine which window has the input focus, compare the window borders. The border color of the active window is different from the others or, on a monochrome display, is darker. Another indication that a window is active is that the keyboard cursor is a solid rectangle; in windows that are not active, the cursor is an outline of a rectangle.
Use the following tests to determine which keyboard focus method you are using. If you position the mouse pointer in a window and that window does not get the input focus, your window manager is configured to use the click-to-focus method. If the border of the window changes, you are using the focus-follows-mouse or focusstrictly-under-mouse method. To determine which of the latter methods you are using, start typing something, with the mouse pointer positioned on the active window. Then move the mouse pointer over the root window and continue typing. If characters continue to appear within the window, you are using focus-followsmouse; otherwise, you are using focus-strictly-under-mouse.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Wednesday, June 9, 2010
Using the Internet to Get Help
The Internet provides many helpful sites related to Linux. Aside from sites that offer various forms of documentation, you can enter an error message from a program you are having a problem with in a search engine such as Google (www.google.com, or its Linux-specific version at www.google.com/linux). Enclose the error message within double quotation marks to improve the quality of the results. The search will likely yield a post concerning your problem and suggestions about how to solve it.
Red Hat Web sites. The Red Hat and Fedora Web sites are rich sources of information. The following list identifies locations that may be of interest:
• Fedora documentation is available at docs.fedoraproject.org.
• Manuals for Red Hat Linux through Linux 9 and RHEL are available at www.redhat.com/docs.
• Various types of support documents and support are available at www.redhat.com/apps/support (requires free registration).
• You can query the Red Hat Knowledgebase at kbase.redhat.com.
• The home pages for Fedora (fedoraproject.org) and RHEL (www.redhat.com) have a wealth of information.
• Fedora/RHEL support forums are online discussions about any Red Hat–related issues that people want to raise. One forum is dedicated to new users; others to Apache, the X Window System, and so on. Go to www.redhat.com/mailman/listinfo to browse the lists. Another site that has similar, useful information is fedoraforum.org.
• The Fedora/RHEL bugs database is available at bugzilla.redhat.com. Anyone can search the database. To submit new bugs or append to existing bugs, you need to sign up for a free account.
• Fedora weekly news is available at fedoraproject.org/wiki/FWN.
• RHEL hardware help is available from the Red Hat hardware catalog at hardware.redhat.com. The hardware that Fedora supports is mostly a superset of that supported by RHEL.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Red Hat Web sites. The Red Hat and Fedora Web sites are rich sources of information. The following list identifies locations that may be of interest:
• Fedora documentation is available at docs.fedoraproject.org.
• Manuals for Red Hat Linux through Linux 9 and RHEL are available at www.redhat.com/docs.
• Various types of support documents and support are available at www.redhat.com/apps/support (requires free registration).
• You can query the Red Hat Knowledgebase at kbase.redhat.com.
• The home pages for Fedora (fedoraproject.org) and RHEL (www.redhat.com) have a wealth of information.
• Fedora/RHEL support forums are online discussions about any Red Hat–related issues that people want to raise. One forum is dedicated to new users; others to Apache, the X Window System, and so on. Go to www.redhat.com/mailman/listinfo to browse the lists. Another site that has similar, useful information is fedoraforum.org.
• The Fedora/RHEL bugs database is available at bugzilla.redhat.com. Anyone can search the database. To submit new bugs or append to existing bugs, you need to sign up for a free account.
• Fedora weekly news is available at fedoraproject.org/wiki/FWN.
• RHEL hardware help is available from the Red Hat hardware catalog at hardware.redhat.com. The hardware that Fedora supports is mostly a superset of that supported by RHEL.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Saturday, May 22, 2010
The History of GNU–Linux
Fade to 1983
Richard Stallman (www.stallman.org) announced1 the GNU Project for creating an operating system, both kernel and system programs, and presented the GNU Manifesto, which begins as follows:
GNU, which stands for Gnu’s Not UNIX, is the name for the complete UNIX-compatible software system which I am writing so that I can give it away free to everyone who can use it.
Some years later, Stallman added a footnote to the preceding sentence when he realized that it was creating confusion:
The wording here was careless. The intention was that nobody would have to pay for *permission* to use the GNU system. But the words don’t make this clear, and people often interpret them as saying that copies of GNU should always be distributed at little or no charge. That was never the intent; later on, the manifesto mentions the possibility of companies providing the service of distribution for a profit. Subsequently I have learned to distinguish carefully between “free” in the sense of freedom and “free” in the sense of price. Free software is software that users have the freedom to distribute and change. Some users may obtain copies at no charge, while others pay to obtain copies—and if the funds help support improving the software, so much the better. The important thing is that everyone who has a copy has the freedom to cooperate with others in using it.
In the manifesto, after explaining a little about the project and what has been accomplished so far, Stallman continues:
Why I Must Write GNU
I consider that the golden rule requires that if I like a program I must share it with other people who like it. Software sellers want to divide the users and conquer them, making each user agree not to share with others. I refuse to break solidarity with other users in this way. I cannot in good conscience sign a nondisclosure agreement or a software license agreement. For years I worked within the Artificial Intelligence Lab to resist such tendencies and other inhospitalities, but eventually they had gone too far: I could not remain in an institution where such things are done for me against my will.
So that I can continue to use computers without dishonor, I have decided to put together a sufficient body of free software so that I will be able to get along without any software that is not free. I have resigned from the AI Lab to deny MIT any legal excuse to prevent me from giving GNU away.
Next Scene, 1991
The GNU Project has moved well along toward its goal. Much of the GNU operating system, except for the kernel, is complete. Richard Stallman later writes:
By the early ’90s we had put together the whole system aside from the kernel (and we were also working on a kernel, the GNU Hurd,3 which runs on top of Mach4). Developing this kernel has been a lot harder than we expected, and we are still working on finishing it.5
...[M]any believe that once Linus Torvalds finished writing the kernel, his friends looked around for other free software, and for no particular reason most everything necessary to make a UNIX-like system was already available. What they found was no accident—it was the GNU system. The available free software6 added up to a complete system because the GNU Project had been working since 1984 to make one. The GNU Manifesto had set forth the goal of developing a free UNIX-like system, called GNU. The Initial Announcement of the GNU Project also outlines some of the original plans for the GNU system. By the time Linux was written, the [GNU] system was almost finished.7
Today the GNU “operating system” runs on top of the FreeBSD (www.freebsd.org) and NetBSD (www.netbsd.org) kernels with complete Linux binary compatibility and on top of Hurd pre-releases and Darwin (developer.apple.com/opensource) without this compatibility.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Richard Stallman (www.stallman.org) announced1 the GNU Project for creating an operating system, both kernel and system programs, and presented the GNU Manifesto, which begins as follows:
GNU, which stands for Gnu’s Not UNIX, is the name for the complete UNIX-compatible software system which I am writing so that I can give it away free to everyone who can use it.
Some years later, Stallman added a footnote to the preceding sentence when he realized that it was creating confusion:
The wording here was careless. The intention was that nobody would have to pay for *permission* to use the GNU system. But the words don’t make this clear, and people often interpret them as saying that copies of GNU should always be distributed at little or no charge. That was never the intent; later on, the manifesto mentions the possibility of companies providing the service of distribution for a profit. Subsequently I have learned to distinguish carefully between “free” in the sense of freedom and “free” in the sense of price. Free software is software that users have the freedom to distribute and change. Some users may obtain copies at no charge, while others pay to obtain copies—and if the funds help support improving the software, so much the better. The important thing is that everyone who has a copy has the freedom to cooperate with others in using it.
In the manifesto, after explaining a little about the project and what has been accomplished so far, Stallman continues:
Why I Must Write GNU
I consider that the golden rule requires that if I like a program I must share it with other people who like it. Software sellers want to divide the users and conquer them, making each user agree not to share with others. I refuse to break solidarity with other users in this way. I cannot in good conscience sign a nondisclosure agreement or a software license agreement. For years I worked within the Artificial Intelligence Lab to resist such tendencies and other inhospitalities, but eventually they had gone too far: I could not remain in an institution where such things are done for me against my will.
So that I can continue to use computers without dishonor, I have decided to put together a sufficient body of free software so that I will be able to get along without any software that is not free. I have resigned from the AI Lab to deny MIT any legal excuse to prevent me from giving GNU away.
Next Scene, 1991
The GNU Project has moved well along toward its goal. Much of the GNU operating system, except for the kernel, is complete. Richard Stallman later writes:
By the early ’90s we had put together the whole system aside from the kernel (and we were also working on a kernel, the GNU Hurd,3 which runs on top of Mach4). Developing this kernel has been a lot harder than we expected, and we are still working on finishing it.5
...[M]any believe that once Linus Torvalds finished writing the kernel, his friends looked around for other free software, and for no particular reason most everything necessary to make a UNIX-like system was already available. What they found was no accident—it was the GNU system. The available free software6 added up to a complete system because the GNU Project had been working since 1984 to make one. The GNU Manifesto had set forth the goal of developing a free UNIX-like system, called GNU. The Initial Announcement of the GNU Project also outlines some of the original plans for the GNU system. By the time Linux was written, the [GNU] system was almost finished.7
Today the GNU “operating system” runs on top of the FreeBSD (www.freebsd.org) and NetBSD (www.netbsd.org) kernels with complete Linux binary compatibility and on top of Hurd pre-releases and Darwin (developer.apple.com/opensource) without this compatibility.
Source of Information : Prentice Hall A.Practical Guide to Fedora and Red Hat Enterprise Linux 5th Edition
Sunday, August 24, 2008
Installing and Running sendmail in Red Hat Linux
The full sendmail distribution consists of three RPM packages: sendmail, sendmail-cf, and sendmail-doc. Only the first package is truly necessary to send and receive mail on your machine. The second package includes configuration macros and other files that can help you reconfigure your site's sendmail installation if the defaults are insufficient. The third package contains documentation files that help to explain some of the details of the current version.
The sendmail binary packages are included in the Red Hat distribution. The sendmail package is on CD #1, while the sendmail-cf package is on CD #2, and the sendmail-doc package is on CD #3. From the Red Hat RPMS directory on each CD-ROM, the following command installs the packages:
# rpm -ivv sendmail*
Starting sendmail
Once installed, the sendmail service is turned on by default. To start sendmail immediately, you can either reboot the machine or just run /etc/init.d/sendmail start to start the server. The procedure for starting and stopping sendmail is no different from that of other server processes.
Other Mail Servers Available for Red Hat Linux
The open-source version of sendmail is not the only mail server available for Red Hat Linux, but it is definitely the most common. Other servers are described in the following list, with URLs that provide further information.
• Postfix — The Postfix MTA is the only mail-server software besides Sendmail that comes with Red Hat Linux. Written by Wietse Venema (of tcp_wrappers fame), this free mail server was designed with security in mind and executes most functions as an unprivileged user in a restricted chroot environment. The server encompasses more than a dozen small programs (each performing a simple, distinct task) and several single-purpose queues. Information and source code can be found at www.postfix.org.
• Exim — The Exim MTA is a free mail server (under GNU) that runs on Linux and other UNIX systems. This MTA includes enhanced protection against unsolicited junk mail and mail bombs. Find out more about Exim from the Exim Home Page (www.exim.org).
• Qmail — Also conceived with security as a high priority, this mail server (written by Daniel J. Bernstein) offers secure and reliable message transfer, mailbox quotas, virtual domains, and antispam features. More information is available from www.qmail.org/top.html.
• Sendmail (commercial version) — Based on the same source code as open-source sendmail, this product is distributed as binary executables built specifically for Red Hat Linux (among other Linux and UNIX variants). Pricing for the Sendmail Advanced Message Server is based on the number of mailboxes you are serving. The product offers simple installation, Web-based management, and support. Details can be found at www.sendmail.com.
• Smail — Smail offers many of the same features as sendmail but is somewhat easier to configure and requires less memory. The source code can be downloaded from ftp://ftp.planix.com/pub/Smail/.
Incoming messages received by sendmail are processed and stored in the /var/spool/mail directory. Each file in this directory represents a valid user name on the local machine. The file is created automatically when you add a user. People with login accounts use this directory and their user account name as their incoming mailboxes (for example, /var/spool/mail/johnq).
Outgoing messages go in /var/spool/mqueue directory while waiting to be sent. Filenames in this directory follow a consistent naming scheme. The first two characters indicate what type of data is stored in the file. Subsequent characters form a unique random identifier based on the PID of the sendmail process that is handling that message.
Other programs
Several other executable programs are included in the distribution.
Logging performed by sendmail
The amount of logging performed by sendmail is configurable in the sendmail.cf file, but the default level provides good coverage of informational notices and error messages. By default, the syslog facility (/etc/syslog.conf file) stores logging information from sendmail in the /var/log/maillog file.
An informational message similar to the following is written in the /var/log/maillog file each time the daemon starts (which also causes the hashed alias database to be regenerated):
Feb 16 12:52:40 toys sendmail[1758]: alias database /etc/aliases
rebuilt by root
Feb 16 12:52:40 toys sendmail[1758]: /etc/aliases: 63 aliases, longest
10 bytes, 625 bytes total
Feb 16 12:52:40 toys sendmail[1787]: starting daemon (8.12.8):
SMTP+queueing@01:00:00
Each time a message is sent or received, a log file entry is created:
Feb 16 12:54:34 toys sendmail[1120]: OAA01120: from=root, size=161,
class=0, pri=3 0161, nrcpts=1,
msgid=<199907191254.oaa01120@toys.linuxtoys.net>, relay=root@localhost
Feb 16 12:54:35 toys sendmail[1127]: OAA01120: to=jkpat, ctladdr=root
(0/0), delay=00:00:01, xdelay=00:00:00, mailer=local, stat=Sent
The logs even show when people attempt things that perhaps they shouldn't try. The wiz and debug commands were implemented in earlier versions of sendmail and were found to be a huge security problem. You may log file entries, such as those shown in the code examples below, as people with malicious intent check to make sure that you're not running a vulnerable sendmail daemon. Also, the expn and vrfy commands (which can be disabled via a configuration option) could give out more information than you'd care to distribute.
Feb 16 13:03:27 toys sendmail[699]: NOQUEUE: "wiz" command from localhost
[127.0.0 .1] (127.0.0.1)
Feb 16 13:03:29 toys sendmail[699]: NOQUEUE: "debug" command from
localhost [127.0 .0.1] (127.0.0.1)
Feb 16 13:03:37 toys sendmail[701]: NOQUEUE: localhost [127.0.0.1]:
expn oracle
Feb 16 13:03:43 toys sendmail[702]: NOQUEUE: localhost [127.0.0.1]:
vrfy oracle
>>> Read more about What is Red Hat Linux SMTP and sendmail <<<
Source of Information : Red Hat Linux Bible: Fedora and Enterprise Edition
The sendmail binary packages are included in the Red Hat distribution. The sendmail package is on CD #1, while the sendmail-cf package is on CD #2, and the sendmail-doc package is on CD #3. From the Red Hat RPMS directory on each CD-ROM, the following command installs the packages:
# rpm -ivv sendmail*
Starting sendmail
Once installed, the sendmail service is turned on by default. To start sendmail immediately, you can either reboot the machine or just run /etc/init.d/sendmail start to start the server. The procedure for starting and stopping sendmail is no different from that of other server processes.
Other Mail Servers Available for Red Hat Linux
The open-source version of sendmail is not the only mail server available for Red Hat Linux, but it is definitely the most common. Other servers are described in the following list, with URLs that provide further information.
• Postfix — The Postfix MTA is the only mail-server software besides Sendmail that comes with Red Hat Linux. Written by Wietse Venema (of tcp_wrappers fame), this free mail server was designed with security in mind and executes most functions as an unprivileged user in a restricted chroot environment. The server encompasses more than a dozen small programs (each performing a simple, distinct task) and several single-purpose queues. Information and source code can be found at www.postfix.org.
• Exim — The Exim MTA is a free mail server (under GNU) that runs on Linux and other UNIX systems. This MTA includes enhanced protection against unsolicited junk mail and mail bombs. Find out more about Exim from the Exim Home Page (www.exim.org).
• Qmail — Also conceived with security as a high priority, this mail server (written by Daniel J. Bernstein) offers secure and reliable message transfer, mailbox quotas, virtual domains, and antispam features. More information is available from www.qmail.org/top.html.
• Sendmail (commercial version) — Based on the same source code as open-source sendmail, this product is distributed as binary executables built specifically for Red Hat Linux (among other Linux and UNIX variants). Pricing for the Sendmail Advanced Message Server is based on the number of mailboxes you are serving. The product offers simple installation, Web-based management, and support. Details can be found at www.sendmail.com.
• Smail — Smail offers many of the same features as sendmail but is somewhat easier to configure and requires less memory. The source code can be downloaded from ftp://ftp.planix.com/pub/Smail/.
Incoming messages received by sendmail are processed and stored in the /var/spool/mail directory. Each file in this directory represents a valid user name on the local machine. The file is created automatically when you add a user. People with login accounts use this directory and their user account name as their incoming mailboxes (for example, /var/spool/mail/johnq).
Outgoing messages go in /var/spool/mqueue directory while waiting to be sent. Filenames in this directory follow a consistent naming scheme. The first two characters indicate what type of data is stored in the file. Subsequent characters form a unique random identifier based on the PID of the sendmail process that is handling that message.
Other programs
Several other executable programs are included in the distribution.
Logging performed by sendmail
The amount of logging performed by sendmail is configurable in the sendmail.cf file, but the default level provides good coverage of informational notices and error messages. By default, the syslog facility (/etc/syslog.conf file) stores logging information from sendmail in the /var/log/maillog file.
An informational message similar to the following is written in the /var/log/maillog file each time the daemon starts (which also causes the hashed alias database to be regenerated):
Feb 16 12:52:40 toys sendmail[1758]: alias database /etc/aliases
rebuilt by root
Feb 16 12:52:40 toys sendmail[1758]: /etc/aliases: 63 aliases, longest
10 bytes, 625 bytes total
Feb 16 12:52:40 toys sendmail[1787]: starting daemon (8.12.8):
SMTP+queueing@01:00:00
Each time a message is sent or received, a log file entry is created:
Feb 16 12:54:34 toys sendmail[1120]: OAA01120: from=root, size=161,
class=0, pri=3 0161, nrcpts=1,
msgid=<199907191254.oaa01120@toys.linuxtoys.net>, relay=root@localhost
Feb 16 12:54:35 toys sendmail[1127]: OAA01120: to=jkpat, ctladdr=root
(0/0), delay=00:00:01, xdelay=00:00:00, mailer=local, stat=Sent
The logs even show when people attempt things that perhaps they shouldn't try. The wiz and debug commands were implemented in earlier versions of sendmail and were found to be a huge security problem. You may log file entries, such as those shown in the code examples below, as people with malicious intent check to make sure that you're not running a vulnerable sendmail daemon. Also, the expn and vrfy commands (which can be disabled via a configuration option) could give out more information than you'd care to distribute.
Feb 16 13:03:27 toys sendmail[699]: NOQUEUE: "wiz" command from localhost
[127.0.0 .1] (127.0.0.1)
Feb 16 13:03:29 toys sendmail[699]: NOQUEUE: "debug" command from
localhost [127.0 .0.1] (127.0.0.1)
Feb 16 13:03:37 toys sendmail[701]: NOQUEUE: localhost [127.0.0.1]:
expn oracle
Feb 16 13:03:43 toys sendmail[702]: NOQUEUE: localhost [127.0.0.1]:
vrfy oracle
>>> Read more about What is Red Hat Linux SMTP and sendmail <<<
Source of Information : Red Hat Linux Bible: Fedora and Enterprise Edition
Monday, July 28, 2008
Background about Red Hat Linux
Several companies and organizations began gathering and packaging Linux software together into usable forms called distributions. The main goal of a Linux distribution is to make the hundreds of unrelated software packages that make up Linux work together as a cohesive whole. For the past few years, the most popular commercial distribution has been Red Hat Linux.
In September 2003, Red Hat, Inc., changed its way of doing business. That change resulted in the formation of the Red Hat–sponsored Fedora Project to take the development of Red Hat Linux technology into the future.
Red Hat forms the Fedora Project
The announcement of the Fedora Project by Red Hat, Inc. at first it prompted more questions than answers about the future direction of the company and its flagship Red Hat Linux product. In fact, it seemed that nothing named Red Hat Linux even existed anymore. Instead, what was Red Hat Linux would be reflected by Linux distributions coming from two paths:
• Fedora Project (http://fedora.redhat.com) — An open source project, beginning from a Red Hat Linux 9 base, that produces its own Linux distribution. While the project is sponsored by Red Hat, Inc., there is no official support for the Linux distribution (called Fedora Core) that the project produces.
• Red Hat Enterprise Linux (www.redhat.com/software/rhel) — An official, commercial Linux product from Red Hat, Inc. that is offered on an annual subscription basis. Red Hat backs up its Enterprise product line with technical support, training, and documentation.
The primary result of the Fedora Project (at least at first) is a set of three binary CDs and three source code CDs of a Linux distribution referred to as the Fedora Core. Before it was called Fedora Core, that distribution was being tested simply as the next in the series of Red Hat Linux distributions (presumably, Red Hat Linux 10).
The name change from Red Hat Linux to Fedora Core wasn't the only differences between the two distributions, however. Red Hat, Inc. also changed its association with the Fedora Core distribution in the following ways:
• No boxed sets — Red Hat decided to not sell Fedora Core through retail channels. The ever-shortening release cycle was making it difficult to manage this, and Red Hat believed that most of its customers were clever enough to download the software.
• No technical support offerings — There are no technical support programs available from Red Hat for Fedora Core, although at the moment you can still purchase the $60/year update service entitlement for Fedora.
• No Red Hat documentation — The set of manuals that came with the previous Red Hat Linux product is not being brought over to Fedora. Instead, a series of small task-oriented documents will be collected for the project in article format.
By not creating a whole support industry around Fedora Core, that project is free to produce software release on a much shorter schedule (possibly two or three times per year). This allows Fedora Core users to always have the latest software features and fixes included with a recent version of the operating system.
Another potential upside to Fedora Core is that the Fedora Project hopes to encourage community software developers to create compatible software. By including software download and installation tools (such as the yum utility) in Fedora Core, the Fedora Project hopes to encourage people to contribute to software repositories that Fedora Core users can rely on to download additional software packages.
Red Hat shifts to Enterprise Linux
The major shift of attention to Red Hat Enterprise Linux as the focus of Red Hat, Inc.'s commercial efforts has been on the horizon for some time. Some characteristics of Red Hat Enterprise Linux are:
• Longer release intervals — Instead of offering releases every 4 to 6 months, Enterprise software will have a 12 to 18 month update cycle. Customers can be assured of a longer support cycle without having to upgrade to a later release.
• Multiple support options — Customers will have the choice of purchasing different levels of support. All subscriptions will include the Update Module, which allows easy access to updates for Red Hat Enterprise Linux systems. The Management Module lets customers develop custom channels and automate management of multiple systems. The Monitoring Module allows customers to monitor and maintain an entire infrastructure of systems.
• Documentation and training — Manuals and training courses will center on the Red Hat Enterprise Linux distribution.
Red Hat Enterprise Linux install types focus on three different types of computer systems, referred to as WS (for workstations), AS (for high-end systems), and ES (for small/mid-range servers). Each system in the Red Hat Enterprise Linux family is meant to be compatible with the others. There are Basic, Standard and Premium editions of these Enterprise systems. While Basic offers only software downloads, standard and premium editions offer hard copy documentation and additional technical support.
Choosing between Fedora and Enterprise
There is so much overlap between Fedora Core and Red Hat Enterprise Linux, Fedora Core provides a way to test out much of the software that is in Enterprise editions.
Although Fedora Core may not be right for everyone, Fedora Core is still great for students, home users, most small businesses, and anyone just wanting to try out Red Hat Linux technology. Larger businesses should seriously consider the implications to support, training, and future upgrade paths before choosing whether to go the Fedora route or sign on with Red Hat Enterprise Linux.
Source of Information : Red Hat Linux Fedora For Dummies
In September 2003, Red Hat, Inc., changed its way of doing business. That change resulted in the formation of the Red Hat–sponsored Fedora Project to take the development of Red Hat Linux technology into the future.
Red Hat forms the Fedora Project
The announcement of the Fedora Project by Red Hat, Inc. at first it prompted more questions than answers about the future direction of the company and its flagship Red Hat Linux product. In fact, it seemed that nothing named Red Hat Linux even existed anymore. Instead, what was Red Hat Linux would be reflected by Linux distributions coming from two paths:
• Fedora Project (http://fedora.redhat.com) — An open source project, beginning from a Red Hat Linux 9 base, that produces its own Linux distribution. While the project is sponsored by Red Hat, Inc., there is no official support for the Linux distribution (called Fedora Core) that the project produces.
• Red Hat Enterprise Linux (www.redhat.com/software/rhel) — An official, commercial Linux product from Red Hat, Inc. that is offered on an annual subscription basis. Red Hat backs up its Enterprise product line with technical support, training, and documentation.
The primary result of the Fedora Project (at least at first) is a set of three binary CDs and three source code CDs of a Linux distribution referred to as the Fedora Core. Before it was called Fedora Core, that distribution was being tested simply as the next in the series of Red Hat Linux distributions (presumably, Red Hat Linux 10).
The name change from Red Hat Linux to Fedora Core wasn't the only differences between the two distributions, however. Red Hat, Inc. also changed its association with the Fedora Core distribution in the following ways:
• No boxed sets — Red Hat decided to not sell Fedora Core through retail channels. The ever-shortening release cycle was making it difficult to manage this, and Red Hat believed that most of its customers were clever enough to download the software.
• No technical support offerings — There are no technical support programs available from Red Hat for Fedora Core, although at the moment you can still purchase the $60/year update service entitlement for Fedora.
• No Red Hat documentation — The set of manuals that came with the previous Red Hat Linux product is not being brought over to Fedora. Instead, a series of small task-oriented documents will be collected for the project in article format.
By not creating a whole support industry around Fedora Core, that project is free to produce software release on a much shorter schedule (possibly two or three times per year). This allows Fedora Core users to always have the latest software features and fixes included with a recent version of the operating system.
Another potential upside to Fedora Core is that the Fedora Project hopes to encourage community software developers to create compatible software. By including software download and installation tools (such as the yum utility) in Fedora Core, the Fedora Project hopes to encourage people to contribute to software repositories that Fedora Core users can rely on to download additional software packages.
Red Hat shifts to Enterprise Linux
The major shift of attention to Red Hat Enterprise Linux as the focus of Red Hat, Inc.'s commercial efforts has been on the horizon for some time. Some characteristics of Red Hat Enterprise Linux are:
• Longer release intervals — Instead of offering releases every 4 to 6 months, Enterprise software will have a 12 to 18 month update cycle. Customers can be assured of a longer support cycle without having to upgrade to a later release.
• Multiple support options — Customers will have the choice of purchasing different levels of support. All subscriptions will include the Update Module, which allows easy access to updates for Red Hat Enterprise Linux systems. The Management Module lets customers develop custom channels and automate management of multiple systems. The Monitoring Module allows customers to monitor and maintain an entire infrastructure of systems.
• Documentation and training — Manuals and training courses will center on the Red Hat Enterprise Linux distribution.
Red Hat Enterprise Linux install types focus on three different types of computer systems, referred to as WS (for workstations), AS (for high-end systems), and ES (for small/mid-range servers). Each system in the Red Hat Enterprise Linux family is meant to be compatible with the others. There are Basic, Standard and Premium editions of these Enterprise systems. While Basic offers only software downloads, standard and premium editions offer hard copy documentation and additional technical support.
Choosing between Fedora and Enterprise
There is so much overlap between Fedora Core and Red Hat Enterprise Linux, Fedora Core provides a way to test out much of the software that is in Enterprise editions.
Although Fedora Core may not be right for everyone, Fedora Core is still great for students, home users, most small businesses, and anyone just wanting to try out Red Hat Linux technology. Larger businesses should seriously consider the implications to support, training, and future upgrade paths before choosing whether to go the Fedora route or sign on with Red Hat Enterprise Linux.
Source of Information : Red Hat Linux Fedora For Dummies
What You Can Do with Red Hat Linux
Linux is freely available software. The source code for Linux, which is the heart and soul of the operating system, is also publicly available. The Free Software Foundation (FSF) contributes much of the utilitarian software that makes using Linux much easier — FSF is the brainchild of the great Richard Stallman.
Red Hat Linux combines all those pieces plus some additional applications and then goes another step and adds a few of its own to create an integrated product. Red Hat, Inc., combines the basic Linux operating system with software (some made by other companies and some made by Red Hat) to produce a package with a value that’s greater than the sum of its parts. That combination is known as a distribution, or flavor, of Linux.
Red Hat Linux was initially used almost solely to provide network services. However, Red Hat started working hard to make Linux suitable for your everyday use. The result is that Red Hat Linux is now used in both server and desktop environments. It’s used by individuals, businesses, and governments to cut costs, improve performance, and just plain get work done.
You can use Red Hat Linux as a desktop workstation, a network server, an Internet gateway, a firewall, the basis of an embedded system (such as a smart VCR or a robot), or even as a multiprocessor supercomputer. And, thanks to the many, many people who continually make refinements and innovations, Red Hat Linux continues to become more flexible and capable with each release.
The Linux operating system has been ported (or converted) from the 32-bit Intel architecture to a number of other architectures, including Alpha, MIPS, PowerPC, and SPARC. This conversion gives users a choice of hardware manufacturers and keeps the Linux kernel flexible for new processors. Linux handles symmetric multiprocessing (it can take on more than one CPU or mathematical and logical programming unit per system box). In addition, projects are in the works to provide sophisticated processing capabilities, such as
Real-time programming: Controlling machinery or test equipment.
High availability: Running a server that needs to work all the time.
Parallel processing: Amplifying the problem-solving power of a computer by using multiple processors to work in parallel. Parallel processing systems come in various flavors, such as Symmetric Multi Processing (SMP), extreme Linux systems, and Beowulf clusters. Research organizations and even individuals can create machines with supercomputer capabilities at a fraction of the price of supercomputers. In certain cases, extreme Linux systems have been made from obsolete PCs, costing the organizations that make them nothing in material costs.
This list shows some cool Red Hat Linux features you can use:
• Desktop productivity tools: Red Hat has successfully worked overtime over the past few years to make Linux work on your desktop. Red Hat bundles software, such as the OpenOffice suite of productivity tools, so that you can get your everyday work done. The OpenOffice suite includes a full-function word processor plus spreadsheet, presentation, graphical drawing, and Web page creation tools. Its word processor can read and write all Windows Office formats plus many others, such as WordPerfect. When you install Red Hat Linux, OpenOffice is installed and icons are placed on the menu bar to make accessing it easy.
• Multimedia stuff: Red Hat Linux packs numerous multimedia tools for you to use. You can play, record, and rip audio tracks from CDs and DVDs. You can listen to streamed media sources, such as radio stations, over the Internet. Linux also lets you transfer photos and other items from your own cameras and MP3 players, for example.
• Network services: Red Hat Linux works as a network-based server too. Linux found its initial popularity performing jobs like Web serving and file and printer sharing and hasn’t missed a beat.
Boosting your personal workstation
We cannot emphasize enough how well Red Hat Linux works as a personal workstation. With Red Hat Linux, you can easily create your own, inexpensive, flexible, and powerful personal workstation. Linux provides the platform for most of the applications you need to get your work done. Many applications come bundled with Red Hat Linux, from desktop productivity suites, to web browsers and multimedia systems, for example.
The following list describes just a few major categories of free software available for Linux, along with some examples of popular programs:
• Office suites: OpenOffice provides a complete desktop productivity suite that includes an advanced word processor, a spreadsheet, and a presentation editor, for example. The OpenOffice word processor can read and write Microsoft Word files, HTML editors, spreadsheet editors, and graphics editors. OpenOffice provides its own file format but also reads and writes Microsoft Office 97, Office 2000, and Office XP files. It also can use other formats, such as Rich Text Format. Check out the site, at www.openoffice.org.
• Multimedia players: Red Hat packages and installs the open source XMMS player. You can use XMMS to play downloaded Ogg/Vorbis files or continuous Ogg/Vorbis streams. You can download the excellent open source MPlayer audio and video player. MPlayer lets you watch DVDs and listen to MediaPlayer streams. You can, alternatively, download a free version of the proprietary RealPlayer, from RealNetworks, to listen to RealAudio streams. The Internet is going nuts with multimedia, and these multimedia players let you get in on the action.
• Running Microsoft Windows applications and environments: You can use Linux to run Windows programs. The WINE (Wine Is Not an Emulator) system facilitates running Windows programs directly under Linux. The commercial VMware workstation product creates a virtual computer within your Linux PC. The virtual machine looks, acts, smells, and performs just like a real computer, but is really just a program running under the Linux operating system. You can install Linux or Windows or both on the virtual machine. Both WINE and VMware create a bridge between Linux and Windows to give you the best of both worlds.
• Web browsers and e-mail clients: The open source browser, Mozilla, is included with Red Hat Linux 10. The nongraphical, text-based lynx and links browsers are included too and come in handy if you’re using an older, slower modem because they don’t require as much speed as Mozilla does. You can use Mozilla or the new Ximian Evolution personal organizer, calendar, and e-mail client.
Using Linux network tools and services
Linux computers can provide many powerful and flexible network services.
• Apache web server: Of all the web servers on the Internet, the majority are run by the open source Apache web server.
• OpenSSH: The open source version of Secure Shell enables you to communicate securely across the Internet. Secure Shell is much safer than Telnet because Secure Shell encrypts your communication when you log in (even when you log in to other computers), making much slimmer the chance that others can discover your passwords and other sensitive information. OpenSSH also provides other authentication and security features and enables you to securely copy files from machine to machine. With OpenSSH, you can prevent people from listening to your communication.
• Internet accessing utilities: Red Hat Linux provides several configuration utilities that help you connect to the Internet. The utilities help you to configure DSL, cable modems, and plain old telephone modems to connect to the Internet. They also help you to connect to Local Area Networks (LAN) using Ethernet adapters.
• Firewalls: A firewall is a system that controls access to your private network from any outside network (in this case, the Internet) and to control access from your private network to the outside world. To keep the bad guys out, Red Hat Linux provides protection by giving you the tools to build your own firewall. Red Hat Linux is flexible in this regard, and many software packages are available, including the popular and simple-to-use netfilter/iptables filtering software.
Source of Information : Red Hat Linux Fedora For Dummies
Red Hat Linux combines all those pieces plus some additional applications and then goes another step and adds a few of its own to create an integrated product. Red Hat, Inc., combines the basic Linux operating system with software (some made by other companies and some made by Red Hat) to produce a package with a value that’s greater than the sum of its parts. That combination is known as a distribution, or flavor, of Linux.
Red Hat Linux was initially used almost solely to provide network services. However, Red Hat started working hard to make Linux suitable for your everyday use. The result is that Red Hat Linux is now used in both server and desktop environments. It’s used by individuals, businesses, and governments to cut costs, improve performance, and just plain get work done.
You can use Red Hat Linux as a desktop workstation, a network server, an Internet gateway, a firewall, the basis of an embedded system (such as a smart VCR or a robot), or even as a multiprocessor supercomputer. And, thanks to the many, many people who continually make refinements and innovations, Red Hat Linux continues to become more flexible and capable with each release.
The Linux operating system has been ported (or converted) from the 32-bit Intel architecture to a number of other architectures, including Alpha, MIPS, PowerPC, and SPARC. This conversion gives users a choice of hardware manufacturers and keeps the Linux kernel flexible for new processors. Linux handles symmetric multiprocessing (it can take on more than one CPU or mathematical and logical programming unit per system box). In addition, projects are in the works to provide sophisticated processing capabilities, such as
Real-time programming: Controlling machinery or test equipment.
High availability: Running a server that needs to work all the time.
Parallel processing: Amplifying the problem-solving power of a computer by using multiple processors to work in parallel. Parallel processing systems come in various flavors, such as Symmetric Multi Processing (SMP), extreme Linux systems, and Beowulf clusters. Research organizations and even individuals can create machines with supercomputer capabilities at a fraction of the price of supercomputers. In certain cases, extreme Linux systems have been made from obsolete PCs, costing the organizations that make them nothing in material costs.
This list shows some cool Red Hat Linux features you can use:
• Desktop productivity tools: Red Hat has successfully worked overtime over the past few years to make Linux work on your desktop. Red Hat bundles software, such as the OpenOffice suite of productivity tools, so that you can get your everyday work done. The OpenOffice suite includes a full-function word processor plus spreadsheet, presentation, graphical drawing, and Web page creation tools. Its word processor can read and write all Windows Office formats plus many others, such as WordPerfect. When you install Red Hat Linux, OpenOffice is installed and icons are placed on the menu bar to make accessing it easy.
• Multimedia stuff: Red Hat Linux packs numerous multimedia tools for you to use. You can play, record, and rip audio tracks from CDs and DVDs. You can listen to streamed media sources, such as radio stations, over the Internet. Linux also lets you transfer photos and other items from your own cameras and MP3 players, for example.
• Network services: Red Hat Linux works as a network-based server too. Linux found its initial popularity performing jobs like Web serving and file and printer sharing and hasn’t missed a beat.
Boosting your personal workstation
We cannot emphasize enough how well Red Hat Linux works as a personal workstation. With Red Hat Linux, you can easily create your own, inexpensive, flexible, and powerful personal workstation. Linux provides the platform for most of the applications you need to get your work done. Many applications come bundled with Red Hat Linux, from desktop productivity suites, to web browsers and multimedia systems, for example.
The following list describes just a few major categories of free software available for Linux, along with some examples of popular programs:
• Office suites: OpenOffice provides a complete desktop productivity suite that includes an advanced word processor, a spreadsheet, and a presentation editor, for example. The OpenOffice word processor can read and write Microsoft Word files, HTML editors, spreadsheet editors, and graphics editors. OpenOffice provides its own file format but also reads and writes Microsoft Office 97, Office 2000, and Office XP files. It also can use other formats, such as Rich Text Format. Check out the site, at www.openoffice.org.
• Multimedia players: Red Hat packages and installs the open source XMMS player. You can use XMMS to play downloaded Ogg/Vorbis files or continuous Ogg/Vorbis streams. You can download the excellent open source MPlayer audio and video player. MPlayer lets you watch DVDs and listen to MediaPlayer streams. You can, alternatively, download a free version of the proprietary RealPlayer, from RealNetworks, to listen to RealAudio streams. The Internet is going nuts with multimedia, and these multimedia players let you get in on the action.
• Running Microsoft Windows applications and environments: You can use Linux to run Windows programs. The WINE (Wine Is Not an Emulator) system facilitates running Windows programs directly under Linux. The commercial VMware workstation product creates a virtual computer within your Linux PC. The virtual machine looks, acts, smells, and performs just like a real computer, but is really just a program running under the Linux operating system. You can install Linux or Windows or both on the virtual machine. Both WINE and VMware create a bridge between Linux and Windows to give you the best of both worlds.
• Web browsers and e-mail clients: The open source browser, Mozilla, is included with Red Hat Linux 10. The nongraphical, text-based lynx and links browsers are included too and come in handy if you’re using an older, slower modem because they don’t require as much speed as Mozilla does. You can use Mozilla or the new Ximian Evolution personal organizer, calendar, and e-mail client.
Using Linux network tools and services
Linux computers can provide many powerful and flexible network services.
• Apache web server: Of all the web servers on the Internet, the majority are run by the open source Apache web server.
• OpenSSH: The open source version of Secure Shell enables you to communicate securely across the Internet. Secure Shell is much safer than Telnet because Secure Shell encrypts your communication when you log in (even when you log in to other computers), making much slimmer the chance that others can discover your passwords and other sensitive information. OpenSSH also provides other authentication and security features and enables you to securely copy files from machine to machine. With OpenSSH, you can prevent people from listening to your communication.
• Internet accessing utilities: Red Hat Linux provides several configuration utilities that help you connect to the Internet. The utilities help you to configure DSL, cable modems, and plain old telephone modems to connect to the Internet. They also help you to connect to Local Area Networks (LAN) using Ethernet adapters.
• Firewalls: A firewall is a system that controls access to your private network from any outside network (in this case, the Internet) and to control access from your private network to the outside world. To keep the bad guys out, Red Hat Linux provides protection by giving you the tools to build your own firewall. Red Hat Linux is flexible in this regard, and many software packages are available, including the popular and simple-to-use netfilter/iptables filtering software.
Source of Information : Red Hat Linux Fedora For Dummies
Sunday, July 27, 2008
Knowing what is Red Hat Linux
With the recent split between community (Fedora) and commercial (Red Hat Enterprise Linux) versions of Red Hat Linux, Red Hat has created a model that can suit the fast-paced changes in the open source world, while still meeting the demands for a well-supported commercial Linux distribution.
Technical people have chosen Red Hat Linux because of its reputation for solid performance. With the new Fedora Project, Red Hat hopes to create an environment where open source developers can bring high-quality software packages to Red Hat Linux that would be beyond the resources of Red Hat, Inc. to test and maintain on its own.
Over 1,400 individual software packages (compared to just over 600 in Red Hat Linux 6.2) are included in the latest release of Red Hat Linux, referred to as Fedora Core. These packages contain features that would cost you hundreds or thousands of dollars to duplicate if you bought them as separate commercial products. These features let you:
• Connect your computers to a LAN or the Internet.
• Create documents and publish your work on paper or on the Web.
• Work with multimedia content to manipulate images, play music files, view video, and even burn your own CDs.
• Play games individually or over a network.
• Communicate over the Internet using a variety of Web tools for browsing, chatting, transferring files, participating in newsgroups, and sending and receiving e-mail.
• Protect your computing resources by having Red Hat Linux act as a firewall and/or a router to protect against intruders coming in through public networks.
• Configure a computer to act as a network server, such as a print server, Web server, file server, mail server, news server, and a database server.
This is just a partial list of what you can do with Red Hat Linux. There are many more features built into Red Hat Linux as well.
Support for new video cards, printers, storage devices, and applications are being added every day. Linux programmers around the world are no longer the only ones creating hardware drivers. Every day more hardware vendors are creating their own drivers, so they can sell products to the growing Linux market. New applications are being created to cover everything from personal productivity tools to programs that access massive corporate databases.
Remember that old Pentium computer in your closet? Don't throw it away! Just because a new release of Red Hat Linux is out doesn't mean that you need all new hardware for it to run. Support for many old computer components get carried from one release to the next. There are old PCs running Red Hat Linux today as routers (to route data between your LAN and the Internet), firewalls (to protect your network from outside intrusion), and file servers (to store shared files on your LAN) — with maybe an Ethernet card or an extra hard disk added.
Source of Information : Red Hat Linux Bible - Fedora And Enterprise Edition
Technical people have chosen Red Hat Linux because of its reputation for solid performance. With the new Fedora Project, Red Hat hopes to create an environment where open source developers can bring high-quality software packages to Red Hat Linux that would be beyond the resources of Red Hat, Inc. to test and maintain on its own.
Over 1,400 individual software packages (compared to just over 600 in Red Hat Linux 6.2) are included in the latest release of Red Hat Linux, referred to as Fedora Core. These packages contain features that would cost you hundreds or thousands of dollars to duplicate if you bought them as separate commercial products. These features let you:
• Connect your computers to a LAN or the Internet.
• Create documents and publish your work on paper or on the Web.
• Work with multimedia content to manipulate images, play music files, view video, and even burn your own CDs.
• Play games individually or over a network.
• Communicate over the Internet using a variety of Web tools for browsing, chatting, transferring files, participating in newsgroups, and sending and receiving e-mail.
• Protect your computing resources by having Red Hat Linux act as a firewall and/or a router to protect against intruders coming in through public networks.
• Configure a computer to act as a network server, such as a print server, Web server, file server, mail server, news server, and a database server.
This is just a partial list of what you can do with Red Hat Linux. There are many more features built into Red Hat Linux as well.
Support for new video cards, printers, storage devices, and applications are being added every day. Linux programmers around the world are no longer the only ones creating hardware drivers. Every day more hardware vendors are creating their own drivers, so they can sell products to the growing Linux market. New applications are being created to cover everything from personal productivity tools to programs that access massive corporate databases.
Remember that old Pentium computer in your closet? Don't throw it away! Just because a new release of Red Hat Linux is out doesn't mean that you need all new hardware for it to run. Support for many old computer components get carried from one release to the next. There are old PCs running Red Hat Linux today as routers (to route data between your LAN and the Internet), firewalls (to protect your network from outside intrusion), and file servers (to store shared files on your LAN) — with maybe an Ethernet card or an extra hard disk added.
Source of Information : Red Hat Linux Bible - Fedora And Enterprise Edition
Wednesday, February 27, 2008
Read Hat Linux related posts
Knowing what is Red Hat Linux
With the recent split between community (Fedora) and commercial (Red Hat Enterprise Linux) versions of Red Hat Linux, Red Hat has created a model that can suit the fast-paced changes in the open source world, while still meeting the demands for a well-supported commercial Linux distribution.
What You Can Do with Red Hat Linux
You can use Red Hat Linux as a desktop workstation, a network server, an Internet gateway, a firewall, the basis of an embedded system (such as a smart VCR or a robot), or even as a multiprocessor supercomputer. And, thanks to the many, many people who continually make refinements and innovations, Red Hat Linux continues to become more flexible and capable with each release.
Background about Red Hat Linux
Several companies and organizations began gathering and packaging Linux software together into usable forms called distributions. The main goal of a Linux distribution is to make the hundreds of unrelated software packages that make up Linux work together as a cohesive whole. For the past few years, the most popular commercial distribution has been Red Hat Linux.
Installing and Running sendmail in Red Hat Linux
he full sendmail distribution consists of three RPM packages: sendmail, sendmail-cf, and sendmail-doc. Only the first package is truly necessary to send and receive mail on your machine. The second package includes configuration macros and other files that can help you reconfigure your site's sendmail installation if the defaults are insufficient. The third package contains documentation files that help to explain some of the details of the current version.
With the recent split between community (Fedora) and commercial (Red Hat Enterprise Linux) versions of Red Hat Linux, Red Hat has created a model that can suit the fast-paced changes in the open source world, while still meeting the demands for a well-supported commercial Linux distribution.
What You Can Do with Red Hat Linux
You can use Red Hat Linux as a desktop workstation, a network server, an Internet gateway, a firewall, the basis of an embedded system (such as a smart VCR or a robot), or even as a multiprocessor supercomputer. And, thanks to the many, many people who continually make refinements and innovations, Red Hat Linux continues to become more flexible and capable with each release.
Background about Red Hat Linux
Several companies and organizations began gathering and packaging Linux software together into usable forms called distributions. The main goal of a Linux distribution is to make the hundreds of unrelated software packages that make up Linux work together as a cohesive whole. For the past few years, the most popular commercial distribution has been Red Hat Linux.
Installing and Running sendmail in Red Hat Linux
he full sendmail distribution consists of three RPM packages: sendmail, sendmail-cf, and sendmail-doc. Only the first package is truly necessary to send and receive mail on your machine. The second package includes configuration macros and other files that can help you reconfigure your site's sendmail installation if the defaults are insufficient. The third package contains documentation files that help to explain some of the details of the current version.
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