|
|
http://www.linuxplanet.com/linuxplanet/print/5745/
内容要点
1. RHEL, redhat 的企业版本
由于 redhat 对软件开发过程的支持，以及对企业用户的完备服务，使得 RHEL 非常有价值，满足了不同对象的需求
2. RHEL 的分类
AS, ES, WS 侧重不同的硬件软件环境
3. 安装过程
图形界面，与 fedora 3 类似，默认使用 lvm。提供了包含 IBM JRE, BEA JRockit, acrobat reader, realplayer, flash, Agfa monotype fonts, Citrix ICA client for Unix, firmware for the Intel 2100 and 2200 wireless adapters, 以及 AT&T's Korn shell 的附加 CD
4. 主要软件包
CUPS 1.1.22, Evolution 2.0.2, Firefox 1.0, GCC 3.4.3, GDB 6.1, GNOME 2.8.0, KDE 3.3.1, Kernel 2.6.9, OpenOffice 1.1.2, OpenLDAP 2.2.13, OpenSSL 0.9.7a, Perl 5.8.5, Python 2.3.14, Ruby 1.8.1, X11(X.org) 6.8.1, Apache 2.0.52, PHP 4.3.9, NFS V4, automounter 4.1, Samba 3.0.10, LVM 2, MySQL 4.1.7, Postgresql 7.4.6, Cyrus IMAPD 2.2.10, exim 4.43, Postfix 2.1.5, Sendmail 8.13, spamassassin 3.0.1, mailman 2.1.5, tons of games
5. 有关 2.6 内核的备注
模块的变化 (.ko), audit, SELinux
附
osnews 给出的另一篇文章(newsforge)的链接和部分内容
Red Hat lacks integrated virtualization features like those found in SUSE Linux Enterprise Server 9 and Solaris 10, and it's more than three times the price of the comparably featured Mandrakelinux Corporate Server 3.0. But Red Hat's most dangerous competition may not be from outside companies, but from its own community distribution. We won't do an in-depth comparison with these distros, as their usefulness is dependent on your specific situation, preference, training, and infrastructure.
Manufacturer Red Hat Inc.
Architectures i386, IA64, AMD64/EM64T, IBM zSeries, S/390 series, and POWER series
License GNU General Public License
Market Enterprise computing, from desktops up to high-end servers
Price (retail) Varies dependent on edition and subscription length
Previous version Red Hat Enterprise Linux 3
Product Web site http://www.redhat.com/software/rhel/
----
Red Hat Enterprise Linux 4.0--The Enterprise Gets An Update
By: Bill von Hagen
Monday, February 14, 2005 12:05:15 AM EST
URL: http://www.linuxplanet.com/linuxplanet/reviews/5745/1/
Enterprise Linux and Red Hat
Red Hat is not only one of the oldest and best known Linux distributions, but is probably the one that has the most traction in the business community thanks to smart people, clever marketing, a steady stream of advertisements, and the introduction of some of the concepts that people take for granted in the commercial Linux space. Many Linux distributions, such as Red Hat, SUSE, Mandrakelinux, and even the ill-fated Caldera Linux distribution, have offered server and desktop products for years, but Red Hat was the first to make a lot of noise about "Linux for the Enterprise," pioneering the label, if not the concept.
Enterprise Linux vendors have to walk the tightrope between providing stable and up-to-date versions of the software packages required in enterprise deployments. Stability is an interesting notion in the Open Source world. On the one hand, you have the legions of dedicated and capable developers who are continually identifying and fixing problems in Open Source software.
On the other hand, you have Linux distribution vendors who are doing the same thing themselves, either by committing resources directly to supporting various software packages or by incorporating patches from the Open Source community. Either way, this is still a net win over proprietary software with a single possible source, a black-box approach to software deployment, and painfully slow release and update cycles.
Red Hat's focus on the Enterprise has had different effects on the desktop and enterprise communities. Desktop users who had previously committed to Red Hat have been split into two communities. One of these is made up of users who feel rejected, are disconcerted about desktop support, and have therefore largely gone elsewhere for supported desktop Linux products.
The flip side of this is the users who are taking advantage of the momentum of the Fedora project and the expertise of its contributors to keep moving forward with the descendant of a popular and widely-used distribution. In enterprise deployments, there's always Red Hat EL Desktop, which is attractive for support reasons and little else.
In the enterprise, most large organizations, except perhaps those with a huge existing commitment to the distribution formerly known as Red Hat N (now end-of-lifed), have seen Red Hat's Enterprise focus as a tremendous win because this has brought enterprise applications vendors such as Oracle into the Linux fold. Businesses can count on Red Hat for enterprise-caliber support and can therefore safely commit to adopting Linux as the heart of their infrastructure without having to worry that they may always have to retain legions of hackers chained in the basement.
Conservative release cycles and a more exhaustive test cycle make Red Hat Enterprise Linux a safer bet for the business community--they don't have to chase the release of the week. And finally, Red Hat's well-known and thoroughly advertised certification and training programs guarantee a certain level of competency and provide the kinds of data points that HR personnel and MIS/IT managers can identify on during the hiring process even if they don't personally know the right questions to ask.
Summary of Red Hat Enterprise Products
Red Hat provides four different products for the Enterprise. Their different server products are identified by two-letter combinations that are supposedly not acronyms, but which I will expand anyway because it's easier to remember them if you have some sort of mnemonic. At the top of the pyramid is Red Hat Enterprise Linux AS, which I think of as their Application server product. Red Hat AS supports systems with up to 16 CPUs and 64GB of main memory. We received a pre-release of the 4.0 version of this product for this review. Red Hat AS is server-rich and comes with various Java bells and whistles that are discussed later in this review.
Moving down the Enterprise Linux food chain is Red Hat Enterprise ES, which I think of as their Enterprise Server product. It supports systems with up to 2 CPUs and 8GB of main memory, and is targeted towards small or medium-sized business server systems who use it to run network, file, print, mail, and Web servers. Next, crossing into the desktop space, is Red Hat Enterprise Linux WS, which I think of as Red Hat Workstation.
WS supports systems with up to 2 CPUs, but does not provide many of the software servers that the higher-level products include. The list of missing servers include FTP, OpenLDAP, DNS/bind, TFTP, PXE, and INN. At the bottom of the Enterprise line comes the RHEL Desktop product, which is sold in quantities of 10, 50, and presumably higher numbers if you'd like. This is designed to run on single-CPU systems with up to 4GB of memory. It includes the things you expect to see on Linux equivalent of a Windows desktop--a mail client (evolution), an office productivity suite (OpenOffice), an instant messenger client (GAIM), a Web browser (Mozilla, currently), and other standards like Adobe Acrobat, Real Player, MacroMedia Flash support, and so on.
Installing RHEL 4
Red Hat Enterprise Linux 4 features a graphically updated version of the familiar Red Hat installation process consisting of two phases. In the first phase, you supply basic information about your system's location and nationalization, specify disk partitioning, select the basic type of installation that you want to perform and any additional packages that you want to install. In the second phase, you confirm the date and time, create user accounts, register with Red Hat Network in order to receive updates, and optionally install additional packages from CD #5, the Red Hat Extras CD. Figure 1 shows the Welcome screen from the RHEL AS 4.0 installer.
One exceptionally clever notion adopted from the Fedora Project is the use of logical volumes in RHEL's default disk partitioning suggestions. Figure 2 shows the default partitioning scheme proposed by the installer on a small system disk. I've appreciated this in Fedora, but it makes even more sense in enterprise deployments where disk space requirements almost always expand and downtime for adding disk space must be kept to a minimum. Using logical volumes by default makes it easy to bring down a system for scheduled maintenance, add new disk drives, and dynamically integrate the space that they provide once the system is running again. The alternative of manually cloning the contents of a partition to another and swapping the partitions during additional downtime is painfully primitive by comparison. More Linux distributions should take this enlightened, sysadmin-sensitive approach to default disk allocation and assignment.
Unlike the Red Hat N products of old, Red Hat EL AS doesn't provide a variety of default installation configurations, which is understandable because of its more focused audience. Your choices are to install the default set of packages or to customize the list of packages that you're installing. I typically do the latter and select "Everything" as my package list because disk space is much cheaper than my time when I find that I'm missing some package on my application server and have to hunt down the CDs, install and configure, and so on.
The Extras CD provided with Red Hat EL AS features an interesting choice of third-party packages divided into three sections--Java and Java Utilities, Multimedia, and Miscellaneous. Your Java choices consist of various selections that make up the IBM Runtime environment and Development kit and the BEA's WebLogic JRockit management console, plugins, and runtime. The Multimedia section contains Adobe Acrobat, Real's RealPlayer, and and Macromedia's Flash plugin. The Miscellaneous section contains Agfa Monotype fonts, the Citrix ICA client for Unix, firmware for the Intel 2100 and 2200 wireless adapters, and AT&T's Korn shell. Miscellaneous, indeed!
What's in the Box
One complaint commonly raised against RHEL is that it lags far behind the state-of-the-art in terms of Linux software. Conservative, well-tested releases are a requirement of a true enterprise Linux distribution, both so that no inconsistencies or problems are introduced into corporate infrastructure and to facilitate the longer product support provided for enterprise editions. At the same time, enterprise distributions need to provide a mechanism for keeping up with fundamental improvements in system software. Some of the versions of software provided with RHEL 3.0, such as OpenLDAP, were old enough that they did not support new and up-to-date features that system administrators need to use this in enterprise deployments. RHEL 4.0 corrects most of these sorts of problems, including a move to the more scalable and powerful 2.6 Linux kernel, but the underlying update/upgrade problem still needs to be addressed beyond vulnerability and bug fixes, which Red Hat seems to do a good job of keeping up with.
The following table shows the versions of some of the most popular GNU/Linux software packages found in Red Hat Enterprise Linux 4.0. For those perhaps new to Linux, this table lists the versions of commonly-used applications and system services such the Common Unix Print Server (CUPS) Evolution mail client, the GCC and GDB packages for compilation and debugging, the GNOME desktop system and the underlying X Window System, the Perl, Python, and Ruby scripting languages, authentication and security packages such as OpenLDAP and OpenSSL, the Open Office desktop office software package, the Linux kernel itself.
Package RHEL 4.0 Version
CUPS 1.1.22
Evolution 2.0.2
Firefox 1.0
GCC 3.4.3
GDB 6.1
GNOME 2.8.0
KDE 3.3.1
Kernel 2.6.9
OpenOffice 1.1.2
OpenLDAP 2.2.13
OpenSSL 0.9.7a
Perl 5.8.5
Python 2.3.14
Ruby 1.8.1
X11(X.org) 6.8.1
Figure 3 shows the default GNOME 2.8 desktop provided by Red Hat Enterprise Linux 4.
From the Web server point of view, RHEL4 provides httpd (Apache) version 2.0.52, with version 4.3.9 of the PHP scripting language and version 2.01 of the cool webalizer software for analyzing web logs and displaying traffic statistics. I didn't try any of the well-known exploits against PHP 4.3.9, but I suspect that an update will be coming soon for that particular package if Red Hat hasn't already patched them into their version. You should do some testing of this before some random Root Crew shows up and gives your brand new site an unwanted face lift.
From the file server point of view, RHEL 4 supports NFS V4, version 4.1 of the autmounter, and version 1.0.6 of the NFS support utilities. It provides Samba version 3.0.10 and supports version 2.00 of the updated Logical Volume Manager LVM2. I was somewhat disappointed with the fact that RHEL 4.0 does not include the utilities for managing the JFS, ReiserFS, or XFS journaling filesystems on local storage. Apparently, Red Hat believes that EXT3 is the only journaling filesystem suitable for managing local storage in the Enterprise. This is clearly untrue, but RHEL doesn't seem to provide any alternatives if you still want to get product support.
Open Source database fans should be happy that RHEL 4.0 provides MySQL 4.1.7 and Postgresql 7.4.6, along with modern versions of the ODBC connectors for each. RHEL 4.0 is also replete with a rich assortment of mail servers, providing Cyrus IMAPD 2.2.10, exim 4.43, Postfix 2.1.5, and Sendmail 8.13. Associated software includes version 3.0.1 of spamassassin for anyone who is deploying any of these mail servers, and includes version 2.1.5 of mailman for creating and managing mailing lists.
As a side note, if you do a custom install of RHEL4 and install everything, it installs a ton of games, which is somewhat surprising in the enterprise Linux Application Server market. However, if your 32-GB 8-CPU application server is under-utilized, you can always play a mean game of battleship (Kbattleship) on the console while configuring services and run-levels, as shows in Figure 4.
RHEL4 and 2.6 Kernel Notes for Sysadmins
The 2.6 Linux kernel has brought many general improvements to Linux system performance, capabilities, and capacity. The most commonly-noted of these are performance and responsiveness improvements, support for greater amounts of memory, better processor utilization and scaling in SMP environments, and integrated support for newer devices and interfaces such as Serial ATA. However, beyond these pleasant and immediately-noticeable improvements, many internal and system-level changes have occurred that enterprise system administrators should be aware of. RHEL4 and the 2.6 kernel provide many other improvements to administrative tools and capabilities - this section highlights my favorites.
Some of the most immediately visible and important changes introduced by the 2.6 Linux kernel are changes to loadable kernel module (LKM) naming conventions, internals, and build models. LKMs now end with the .ko extension (kernel object) to differentiate them from standard object files, have a simpler Makefile/build structure, and can more easily be built outside the kernel source by simply referring to the base location of a writable kernel source tree. If you are currently using devices whose drivers were supplied by a hardware or software vendor, you will need to obtain 2.6 versions of those drivers (assuming that they have not been folded into the official 2.6 kernel source).
Beyond server improvements and enhancements, RHEL4 and the 2.6 kernel give system administrators new levels of access control and system event monitoring. By using a recent version of the 2.6 kernel, RHEL4 introduces support for the light-weight auditing framework that provides interfaces that lower the overhead of providing audit information from the kernel and system applications. I couldn't find the audit daemon or associated applications on RHEL4, but at least the framework is present in the kernel--mechanisms for taking advantage of it can be distributed and RHEL4 updates, I suppose.
More importantly (and usable immediately), RHEL4 supports Security-Enhanced Linux (SELinux), which can be deactivated during the install process but is active by default. SELinux provides a variety of mechanisms for implementing and enforcing access control policies, including those based on the type of object being accessed (type-based) or on the role of the user attempting to access an object (role-based, commonly known as Role-Based Access Control, RBAC). SELinux access control policies operate outside the standard Linux protection and access control mechanisms, and are designed to limit user programs and system servers to the minimum privileges that they require in order to perform their tasks. A correct SELinux policy implementation can go a long way towards limiting the potential damage that can be done by exploiting server or application vulnerabilities through common techniques such as buffer overflows.
Wrapping Up
RHEL4 is a huge step forward for Red Hat and should be a breath of fresh air to businesses who require the stability and support associated with and enterprise Linux distribution, but desperately needed or wanted new versions of the kernel, servers, and applications. If you were waiting for newer features or software to appear in the Enterprise Linux space, Red Hat Enterprise Linux 4 is well worth a look. If you're already a RHEL customer, run, don;t walk, to your support representative for an upgrade.
Bill von Hagen is the author of numerous books and articles on Linux. For more information about Bill, see http://www.vonhagen.org.
Copyright © 1999 internet.com Corp. All Rights Reserved. |
|
IP卡
狗仔卡
发表于 2005-2-15 16:42:47
提升卡
置顶卡
沉默卡
喧嚣卡
变色卡
显身卡
发表于 2005-2-18 14:21:28