RHEL 5 Essentials. Red Hat Enterprise Linux 5 Essentials

Transcription

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2 Red Hat Enterprise Linux 5 Essentials 2

3 Red Hat Enterprise Linux 5 Essentials First Edition 2010 Payload Media. This ebook is provided for personal use only. Unauthorized use, reproduction and/or distribution strictly prohibited. All rights reserved. The content of this book is provided for informational purposes only. Neither the publisher nor the author offers any warranties or representation, express or implied, with regard to the accuracy of information contained in this book, nor do they accept any liability for any loss or damage arising from any errors or omissions. Find more ebooks online at 3

4 Table of Contents Chapter 1. About RHEL 5 Essentials Chapter 2. Installing RHEL 5 on a Clean Disk Drive Obtaining the Red Hat Enterprise Linux Installation Media Installing Red Hat Enterprise Linux Partitioning a Disk for RHEL Configuring Networking Settings Timezone and the Root Password Package Selection The Physical Installation Final Configuration Steps Chapter 3. Performing an RHEL 5 Network Installation RHEL Network Installation Requirements Obtaining a Network Boot Image Configuring the Network Installation Starting the Red Hat Enterprise Linux 5 Network Installation Chapter 4. Installing RHEL 5 with Windows in Dual Boot Environment Partition Resizing Shrinking a Windows XP Partition Choosing an Operating System at Boot Time Editing the RHEL Boot Menu Accessing the Windows Partition from RHEL Chapter 5. Allocating a Windows Disk Partition to RHEL Deleting the Windows Partition from the Disk Formatting the Unallocated Disk Partition Editing the Boot Menu Mounting the New Partition Chapter 6. Logging into the RHEL 5 GNOME Desktop

5 Chapter 7. Configuring RHEL 5 GNOME Screen Resolution and Multiple Monitors Configuring the RHEL Display Resolution Configuring Multiple Monitors Chapter 8. A Guided Tour of the RHEL 5 GNOME Desktop The RHEL 5 GNOME Desktop The Desktop Background The Desktop Panels Chapter 9. Configuring the RHEL 5 GNOME Desktop Background Changing the RHEL 5 GNOME Desktop Background Selecting a Background from the Wallpaper List Creating a Solid or Graded Background Specifying a Background Image Chapter 10. Installing and Customizing RHEL 5 Desktop Themes What is a Desktop Theme? Changing the RHEL 5 Desktop Theme Downloading and Installing a Theme Creating a Custom RHEL Theme Package Summary Chapter 11. Configuring RHEL 5 Desktop Fonts Font Options on RHEL Changing Font Settings Font Rendering Settings RHEL Advanced Font Rendering Accessing the System Font Folder Chapter 12. Configuring the RHEL 5 GNOME Desktop Panels What are Desktop Panels Changing the Position of a Panel Adding and Deleting Desktop Panels

6 12.4 Changing the Appearance of a Desktop Panel Adding Items to a RHEL 5 GNOME Desktop Panel Adding Menus to a Panel Changing the Number of RHEL Desktop Workspaces Chapter 13. Configuring the RHEL 5 Desktop Menu System Customizing an RHEL Desktop Menu Moving Menu Items Adding and Deleting a Menu Item Chapter 14. Browsing My Computer, Files and Folders on the RHEL 5 Desktop Accessing Nautilus Nautilus and the Computer Icon Adding Emblems to Files and Folders Changing File and Folder Permissions Renaming and Deleting Files and Folders Chapter 15. Configuring the RHEL 5 File Manager Displaying Icons or Lists Configuring the List View Configuring the Icon View Chapter 16. RHEL 5 Desktop Startup Programs and Session Configuration Session Managed and Non-Session Managed Programs Understanding Sessions Creating a New Session Configuring Session Preferences Configuring the Current Session Configuring Startup Programs Chapter 17. RHEL 5 Desktop Keyboard Shortcuts Viewing Keyboard Shortcuts Changing a Shortcut

7 17.3 Disabling a Keyboard Shortcut Chapter 18. Configuring RHEL 5 Runlevels and Services Understanding RHEL Runlevels Understanding RHEL Services RHEL Runlevels Descriptions Configuring the Default RHEL Runlevel Changing the Current Runlevel from within a Running RHEL System Identifying Services that Start at Each Runlevel Changing the Services for a Runlevel Chapter 19. Managing RHEL 5 Users and Groups Adding a New User to am RHEL System Editing the Properties of a User Deleting a User from an RHEL System Adding a New Group to an RHEL System Modifying an RHEL Group Deleting a Group from an RHEL System Chapter 20. Basic RHEL 5 Firewall Configuration Configuring a Basic RHEL 5 Firewall Enabling and Disabling the Firewall Configuring Firewall Port Settings Configuring Other Ports Firewall Configuration from a Terminal using lokkit Trusted Interfaces Masquerading Chapter 21. Remote Access to the RHEL 5 Desktop Installing Remote Desktop Support Activating Remote Desktop Access Secure and Insecure Remote Desktop Access

8 21.4 Firewall Configuration Accessing a Remote RHEL Desktop using vncviewer Accessing a Remote RHEL Desktop from a Windows System Establishing a Secure Remote Desktop Session Establishing a Secure Remote Desktop Session from a Windows System Creating Additional Desktops Shutting Down a Desktop Session Configuring the Remote Desktop Environment Chapter 22. Configuring RHEL 5 Remote Access using SSH Installing SSH on an RHEL System Configuring the RHEL Firewall to Allow SSH Connections Using SSH on RHEL Copying files using SSH Disabling the SSH Server Chapter 23. Displaying RHEL 5 Applications Remotely (X11 Forwarding) Requirements for Remotely Displaying RHEL Applications Remotely Displaying an RHEL Application Trusted X11 Forwarding Compressed X11 Forwarding Chapter 24. Using NFS to Share RHEL 5 Folders with Remote Linux and UNIX Systems Ensuring NFS Services are Running on RHEL Configuring the RHEL Firewall to Allow NFS Traffic Specifying the Folders to be Shared Accessing Shared RHEL Folders Mounting an NFS Filesystem on RHEL System Startup Unmounting an NFS Mount Point Chapter 25. Sharing Files Between RHEL 5 and Windows Systems with Samba Samba and Samba Client

9 25.2 Installing Samba on an RHEL System Starting the Samba Service on RHEL Configuring the RHEL Firewall to Enable Samba Configuring Samba Users and Resource Sharing Accessing Windows Shares from RHEL Chapter 26. Configuring an RHEL 5 Based Web Server Requirements for Configuring an RHEL 5 Web Server Installing the Apache Web Server on RHEL Starting the Apache Web Server Testing the Web Server Configuring the Apache Web Server for Your Domain Web Server and Firewall Issues Chapter 27. Configuring an RHEL 5 Postfix Server The structure of the System Mail User Agent Mail Transfer Agent Mail Delivery Agent SMTP Configuring an RHEL System Postfix Pre-Installation Steps Installing Postfix on RHEL Configuring Postfix Starting Postfix on an RHEL System Chapter 28. Installing and Configuring RHEL 5 Xen Virtualization Full Virtualization vs. Para-Virtualization Checking Xen Hardware Compatibility Adding the Red Hat Enterprise Linux 5 Virtualization Channel to the System Preparing RHEL for Xen Virtualization

10 28.5 Building an RHEL Xen Guest System Summary Chapter 29. Using Xen Full Virtualization to Run Windows on RHEL Hardware Requirements for Xen-based Full Virtualization on RHEL Preparing the Installation Image Creating the New Virtual Machine Configuring Xen Virtualization Method Selecting Installation Media Configuring Storage Configuring Network Access CPU and Memory Allocation Creating and Starting the New Xen Virtual Machine Chapter 30. Managing and Monitoring RHEL 5 based Xen Guest Systems Starting and Stopping Xen Guest Systems Pausing an RHEL 5 Xen Guest Operating System Changing Xen Guest Operating System Settings Monitoring Virtual Machine Performance Chapter 31. Configuring a New RHEL 5 Xen Virtual Network RHEL Xen Guest Networking Options Identifying the Settings of an Existing RHEL Xen Virtual Network Creating a New Xen Virtual Network on an RHEL Host Assigning the New Virtual Bridge during Virtual Machine Creation Changing an Existing Virtual Machine to Use a new Virtual Network Chapter 32. Managing Xen on RHEL 5 using the xm and virsh Command-line Tools xm Command-line vs virsh Shell Listing Guest System Status Starting a Xen Guest System Connecting to a Running Xen Guest System

11 32.5 Shutting Down a Guest System Pausing and Resuming a Guest System Suspending and Resuming an RHEL Guest OS Saving and Restoring Xen Guest Systems Rebooting a Guest System Configuring the Memory Assigned to a Xen Guest OS Migrating a Domain to a Different Host Chapter 33. Installing KVM Virtualization on RHEL KVM Hardware Requirements bit Support for KVM on RHEL Adding the Red Hat Enterprise Linux 5 Virtualization Channel to the System Preparing RHEL for KVM Virtualization Verifying the KVM Installation Chapter 34. Creating an RHEL 5 KVM Networked Bridge Interface RHEL 5 Virtual Networks and Network Bridges Creating a Network Bridge Configuring an RHEL 5 Firewall for a Network Bridge Configuring a Virtual Machine to use the Network Bridge Chapter 35. Creating an RHEL 5 KVM Virtual Machine Starting the Virtual Machine Manager Creating the New RHEL 5 based KVM Virtual Machine Configuring the Installation Method Configuring the KVM Virtual Storage Configuring KVM Network Settings Configuring KVM Virtual Machine Memory and CPU Settings Starting the New KVM Virtual Machine Chapter 36. Creating Xen and KVM RHEL 5 Virtual Machines from the Command-line (virtinstall and virsh)

12 36.1 Running virt-install to build the Xen or KVM Guest System An Example RHEL 5 virt-install Command Starting and Stopping a Virtual Machine from the Command Line Creating a Virtual Machine from a Configuration File Chapter 37. Managing and Monitoring RHEL 5 based KVM Guest Systems Starting and Stopping RHEL based KVM Guest Systems Pausing a KVM Guest Operating System Changing KVM Virtual Guest System Settings Monitoring Virtual Machine Performance Monitoring Host Performance Chapter 38. Adding a New Disk Drive to an RHEL 5 System Mounted File Systems or Logical Volumes Getting Started Finding the New Hard Drive in RHEL Creating Linux Partitions Creating a File System on an RHEL Disk Partition Mounting a File System Configuring RHEL 5 to Automatically Mount a File System Chapter 39. Adding a New Disk to an RHEL 5 Volume Group and Logical Volume An Overview of Logical Volume Management (LVM) Volume Group (VG) Physical Volume (PV) Logical Volume (LV) Physical Extent (PE) Logical Extent (LE) Getting Information about Logical Volumes Adding Additional Space to an RHEL Volume Group from the Command Line Chapter 40. Adding and Managing RHEL 5 Swap Space

13 40.1 What is Swap Space? Recommended Swap Space for RHEL Identifying Current Swap Space Usage Adding a Swap File to an RHEL System Adding Swap to an RHEL LVM Swap Volume Adding Swap Space to the Volume Group Chapter 41. Related ebook Publications

14 Chapter 1. About RHEL 5 Essentials Arguably one of the most highly regarded and widely used enterprise Linux distributions available today is Red Hat Enterprise Linux (RHEL). It is considered to be amongst the most stable and reliable operating systems and is backed by the considerable resources and technical skills of Red Hat, Inc. RHEL 5 Essentials is designed to provide detailed information on the use and administration of the Red Hat Enterprise Linux 5 distribution. For beginners, the book covers the basics of configuring the desktop environment, resolving screen resolution issues and configuring and web servers. Installation topics such as network installation and dual booting with Microsoft Windows are covered together with all important security topics such as configuring a firewall and user and group administration. For the experienced user, topics such as remote access, logical volume management (LVM), disk partitioning, swap management, Xen and KVM virtualization, Secure Shell (SSH) and file sharing using both Samba and NFS are covered in detail to provide a thorough overview of this enterprise class operating system. 14

15 Chapter 2. Installing RHEL 5 on a Clean Disk Drive The first step on the path to learning about Red Hat Enterprise Linux involves installing the operating system. RHEL can be installed either in a clean disk environment (where an entire disk is cleared of any existing partitions and dedicated entirely to RHEL) or in a dual boot environment where RHEL co-exists with another operating system on the disk (typically a member of the Microsoft Windows family of operating systems). In this chapter we will be covering the clean disk approach to installation. Dual boot installation will be covered in Installing RHEL 5 with Windows in Dual Boot Environment. 2.1 Obtaining the Red Hat Enterprise Linux Installation Media Although RHEL is an open source operating system, and as such, the source code is freely downloadable, the binary installation images are only available as part of a paid Red Hat Enterprise Linux subscription. In addition to access to the installation images for RHEL, this subscription also provides technical support for the operating system. If you already have a paid subscription, log into your Red Hat account to download the operating system. If you would like to try out RHEL before purchasing, Red Hat provides a 30-day trial. To register for a trial, visit the Red Hat website at and complete the registration process. The installation distribution can be downloaded as either six individual CDROM images or a single DVD image. Unless you specifically need to use CD images the DVD installation image is strongly recommended. The DVD image is named using the following convention: rhel-<variant>-<version>-<architecture>-bin-dvd.iso For example, the RHEL 5.5 server DVD image for 64-bit systems is named as follows: rhel-server-5.5-x86_64-dvd.iso The CDROM images, on the other hand, are named as follows: rhel <variant>-<version>-<architecture>-bin-discn.iso Having downloaded either DVD or CDROM images, either burn them to disk, configure your virtualization environment to treat them as DVD or CDROM drives or use the steps outlined in Performing an RHEL 5 Network Installation to access the installation image over a network. 15

16 2.2 Installing Red Hat Enterprise Linux Insert either the RHEL DVD or disk 1 of the CDROM collection into the appropriate drive and power on the system. If the system tries to boot from the hard disk drive you will need to enter the BIOS set up for your computer and change the boot order so that it boots from the CD or DVD drive first. Once the system has booted you will be presented with the following screen: Installation may be performed using either the graphical or text mode installers. To install using the graphical installer, simply press the <Enter> key. To use the text installer type linux text followed by the <Enter> key. The RHEL installer will then provide the option to test the installation media for errors. Use the arrow keys to navigate between the options and make a selection with the <Enter> key. After a short delay the first screen of the graphical installer will appear. Click on the Release Notes button if you would like to learn about any key features or problems that exist in this release of RHEL. Navigate through the next few pages to configure your preferred language and keyboard type until you reach the partitioning screen. During these steps you may be prompted to enter an Installation Number. If you have a subscription that includes additional packages, enter that number here so that those packages may be accessed during the installation process. 16

17 2.3 Partitioning a Disk for RHEL When you reach the disk partitioning phase of the installation, the installer will present a screen similar to the one illustrated in the following figure: The drop down menu provides a number of options in terms of how the disk will be used to accommodate the RHEL installation: Remove all partitions on selected drives and create default layout - The entire disk drive will be assigned to the RHEL installation. Any pre-existing partitions, together with any existing operating systems and associated data files contained therein will be deleted to make room for RHEL. This option should only be used if you are absolutely sure you no longer need anything that is currently stored on that disk, or have already backed up all user files. Remove Linux partitions on selected drives and create default layout - If the drive was previously configured to support a Windows/Linux dual boot environment or was devoted entirely to another Linux installation, this option may be selected to instruct the installer to delete the pre-existing Linux partition and replace it with RHEL, leaving the non-linux partitions intact. Once again, it is important to backup any user data that may still be needed. 17

18 Use free space on selected drives and create default layout - If the current partitions on the drive do not take up the entire disk space available, any unallocated space may be assigned to the RHEL installation using this option. Create custom layout - When selected, this option displays the disk partitioning tool allowing each partition on the disk to be manually configured. For the purposes of this chapter we are assuming the entire disk is available to accommodate the RHEL installation so select the Remove all partitions on selected drives and create default layout menu option. Beneath the partition menu is the option to encrypt the system. The choice of whether to use encryption will depend on the purpose for which the system is being used, its physical location and type of data it is going to store. Keep in mind that as with any form of encryption there are performance overheads associated with selecting this option. Having made the partitioning selection, choose which disk drives detected on your system are to be used for the installation and click Next to begin the partitioning process. 2.4 Configuring Networking Settings After the disk partitioning and encryption decisions have been made the installer will prompt for some networking configuration information. If your system resides on a network served by a DHCP server (a server or device that automatically assigns network IP addresses to computers on the network) you should leave the default settings unchanged in the Network Devices section of the screen. If you need to manually specify an IP address, select the network device from the list and click on the Edit button to display the Edit Interface dialog and enter your IP address and netmask information, then close the dialog and enter the gateway and DNS settings for your network into the Miscellaneous settings section of the main screen. If you manually specified your IP address, or have a DHCP server that does not automatically provide clients with host names, select the option to manually specify the host name and enter it into the text box and click Next to proceed. 2.5 Timezone and the Root Password On the Timezone screen, make a selection corresponding to your geographical location. The option is also provided to use UTC which automatically adjusts the time to account for daylight savings time. If the computer on which RHEL is being installed also runs another operating system which already uses UTC (such as Windows), leave this option unselected. 18

19 On the next screen, enter a password for the root account on the system. The root, or superuser account is a special user that has administrative privileges on the system. Whilst you will generally use your own account to log into the system, you will need to gain root privileges in order to configure the system and to perform other administrative tasks. 2.6 Package Selection Linux is a modular operating system in that it provides a basic operating system kernel and infrastructure upon which a range of different packages may be installed depending on your specific requirements for the system. If, for example, you plan on using the system as a web server you would need to install the Apache web server package. At this point in the installation the installer needs us to decide which packages should be installed along with the base operating system and displays the screen shown in the following figure: The exact options displayed will depend in part on the specific RHEL installation image that was downloaded from the Red Hat web site. This screen allows you to make general choices about the type of functions you need the system to perform. 19

20 To view or modify the specific package selections, make sure that the Customize Now option is selected before proceeding. You will then be provided a complete overview of which packages are selected for installation and which are not together with the ability to make changes to these selections. Don t worry too much about getting this exactly right at this stage. Packages can be added and removed at any time after the installation is complete by selecting the desktop Applications -> Add/Remove Software menu option. 2.7 The Physical Installation Having made the appropriate package selections, clicking Next will display a screen indicating that the installation will begin and that a log file and kickstart file can be found on the system after installation is complete. The log file will be useful to identify any errors that occurred during the installation, and the kickstart file can be used to install RHEL on other systems using the exact same configuration created here. During the installation process, the installer will format and partition the disk drive, provide a running commentary of the selected packages as they are installed and a progress bar. If you are installing from the 6 RHEL CDROM images as opposed to the single DVD you will need to insert the additional CDs when prompted to do so. If you are using the DVD the installation will complete without further interaction. Once the installation process is complete a screen will appear containing a button to reboot the system. Remove the installation media and click the button. 2.8 Final Configuration Steps After the system has started for the first time, the RHEL Setup Agent will appear with a welcome message. Click on the Forward button to display licensing information followed by the Firewall settings. By default all ports are closed on the firewall with the exception of the ssh port which allows you to remotely log into the system. The topic of firewall configuration will be covered in more detail in the chapter entitled Basic RHEL Firewall Configuration so for now leave the default settings unchanged. Leave SELinux configured as Enforcing to ensure the most secure environment. Choose whether or not to enable Kdump support and then work through the remaining screens to create a user account for yourself and verify the date and time. If you would like the date and time of your RHEL system to be synchronized with an external Network Time Protocol server, select the Synchronize date and time over network option before proceeding. On the Setup Software Updates screen, register the system with the Red Hat Network (RHN). This enables additional packages to be installed from the RHN repositories and also allows the system to receive software updates. In order to register the system, enter your RHN user login 20

21 and password when prompted. If you would prefer to register the system at a later time, do so simply by running the rhn_register command from a terminal window. Having worked through all the set up pages, click Finish to exit the setup agent and log in using your newly created account credentials. 21

22 Chapter 3. Performing an RHEL 5 Network Installation In addition to installing directly from the physical Red Hat Enterprise Linux 5 installation media (in the form of a CDROM or DVD) it is also possible to perform a network based RHEL installation whereby the installation image is installed on a remote server and downloaded in packages to the destination computer system during installation. RHEL currently supports installation via HTTP, FTP and NFS. For the purposes of this tutorial we will focus on the use of HTTP (in other words the installation image is available via a web server on a remote host) though the concepts are largely the same for the other network installation options. 3.1 RHEL Network Installation Requirements Before a network installation of RHEL can be performed a number of items are required. Firstly, the RHEL installation image must be loaded onto the remote server and mounted. If the installation media is in the form a CDROM or DVD then the image can be read from that media into a disk based ISO image file using the dd command as follows: dd if=/dev/media of=/path/to/iso/file/rhel5-image.iso Note that in the above example, /dev/media would be replaced by the path to the CDROM device and /path/to/iso/file/ represents the path to a suitable location on the file system to create the image file. Also keep in mind that the installation media may comprise multiple disk images, each of which will need to be imported into the server. Having created the ISO image file from the installation media, it now needs to be mounted in a location that is accessible to the web server, ftp server or NFS mount point so that it is accessible to the target system. This is achieved using the mount loopback interface: mount -o loop rhel5_image.iso /path/to/mount/point In this case, /path/to/mount/point is replaced by the full path to the location where the RHEL installation image is to be mounted such that it can be accessed via the chosen network installation method. For example, in the case of an HTTP based installation, the chosen mount point might be /var/www/html/rhel5. Note that the specified mount point directory must already exist before executing this command. 3.2 Obtaining a Network Boot Image Once the remote server is configured with a copy of the RHEL 5 installation image, the next step is to plan how the installation process will be initiated on the target system. Clearly we will still need to be able to boot from something locally to start the installation. One option is to boot 22

23 from disk 1 of the six set CDROM installation suite. Alternatively, take the boot.iso file from the images subdirectory of either the disk 1 CDROM or the installation DVD and burn it to a CDROM or DVD and then boot from that. 3.3 Configuring the Network Installation When the installer has booted enter the following command at the boot: prompt and press the enter key: linux askmethod A sequence of screens will subsequently appear providing the opportunity to select a language and keyboard type. Once these settings have been defined, a screen will appear requesting the location of the installation media: Depending on the method by which the installation images are being served by the remote system select either NFS image, FTP or HTTP. For the purposes of this tutorial we will assume the use of HTTP. Once the installation method has been selected, click OK to proceed to the TCP/IP configuration screen. If the computer has multiple network adaptors, select the one to be used during the installation. On the next screen, configure the required IPv4 and IPv6 settings for the network to which the computer is attached: 23