Chapter 4 Installing Linux |
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Installing a boot manager
2.16 Install boot loader (e.g., LILO, MBR vs. first sector of boot partition)
The next selection in the Red Hat Linux installation is to choose the type of boot loader and its location. A boot loader is used to boot the operating system into the intended operating system, which is achieved by loading a bootstrap onto the hard drive. This bootstrap then tells the computer system where to find the next part of the operating system to be loaded. Sometimes the bootstrap will reference a menu that allows the computer system to choose from several operating systems. LILO is the default boot loader on most Linux systems; however, GRUB is also an option. GRUB is a multi-system boot loader created by the GNU project. There are also commercial products that can provide this bootstrap and can be used as the boot loader or boot manager for a Linux system. LILO, or Linux Loader, is used to boot the system into Linux and also provides many tools for troubleshooting a system that does not boot properly. LILO can be used to boot backup copies or different versions of the operating system’s kernel, and it can, as previously stated, allow for a dual boot of the Linux operating system and another operating system. Using LILO to perform the duties of a boot loader is fairly straightforward, but be aware of a couple of notable points:
The location of the bootstrap can be placed in the Master Boot Record (MBR) or the first sector of the boot partition. The Master Boot Record is generally used, but on some systems that are running multiple operating systems, this may not be the best selection because LILO may not work properly with the other operating system.
Because Microsoft Windows NT and 2000 uses NTFS as the file system, LILO won’t be able to boot the Microsoft system. This is not true of Microsoft Windows NT installations that use FAT 16 partitions or Microsoft Windows 2000 installations that use Win98 FAT 32 partitions. In situations were LILO is not loaded in the Master Boot Record, the first boot block of the drive containing Linux is usually used.
When planning to Dual-Boot Linux with any other product, back up the data on the existing operating system before proceeding with the second operating system installation.
Figure 4-8 illustrates the screen that Red Hat uses to determine were LILO is loaded (if it is loaded at all). The installation of LILO can be bypassed if another boot loader is used, such as GRUB or a commercial product.
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Figure 4-8: The Red Hat LILO configuration screen
Creating the Boot Diskette
The next noticeable feature included with the Red Hat installation and in most distributions is the option to make a bootable diskette that can be used to recover a non-bootable system, or to boot the system if LILO is not installed in the Master Boot Record (MBR). Finally, the installer must select the default system to be booted. On a system that may have both Microsoft Windows 98 and Linux, LILO can be set to boot either system by default with the option to boot the other one. This is a useful tool for those who want to run Linux but have a desire or need to use Microsoft or other operating systems. After LILO, GRUB, or another boot manager has been determined and loaded, the system will be able to boot Linux or any other operating system.
Chapter 4 Installing Linux 101
Networking
2.8 Select appropriate networking configuration and protocols (e.g., modems, Ethernet, Token-Ring)
At this point, the operating system is now bootable, so the next step in the Red Hat installation is to set up networking. Networking is what Linux was created to do; because Linux is a UNIX-like operating system, it has inherited the powerful TCP/IP features of UNIX and uses them by default. Although this isn’t the next step in every Linux distribution, the choices are all very similar to the Red Hat installation menus. Networking is detected during the initialization of the system and is therefore presented from the installer at this stage. The network card that is detected is given an interface name. In this case, the name is eth0, as shown in Figure 4-9, but it can also be given interface names that map to other protocols such as token ring, FDDI, or PPP (or PPPoE used with some xDSL cards) if using a modem or other device. Although this can be accomplished with a modem, not all Linux distributions configure modem networking during installation.
Figure 4-9: The Red Hat network configuration screen
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To configure the Ethernet card, the installer must have information about the availability of Dynamic Host Configuration Protocol, (DHCP), which allows the system to lease an IP address for a limited amount of time. The lease is renewed if the client requests an update before the lease expires and if the server approves the renewal. Therefore, if a DHCP server is available, this is usually the easiest and best option for configuring an Ethernet NIC, or network interface card. If a DHCP server is not available, then a static address must be used; otherwise, networking will not start. Usually, if static addresses are used, a network administrator controls which addresses are used and on what equipment. A request for an IP address from the network administrator will generally result in an IP address for the system. That IP address will have the format of 4 octets of information. This can be in binary, hex, or decimal form, but is usually in decimal and is seen when you ping an address. For this example, I use 192.168.0.50, which is part of a class C address and uses a subnet mask of 255.255.255.0 by default.
The subnet mask is used to break up groups of computers so that they can work more effectively on the network. After the IP and subnet mask have been input, the system will complete the network and broadcast sections. The installer will then need to input the Hostname of the system that will ID the system, the Gateway (usually a router) that will usually provide access to the Internet or intranet, and up to three DNS (domain name system) that will be used to resolve machine names to IP addresses. After all these networking items are configured, the system should be ready to work on the network. Although the networking is configured, the security of the networking is not complete until a firewall setting has been selected. This firewall setting is set to low, medium, or high; here is a breakdown of each setting:
Low security allows all services access to the machine and is usually only used in a closed environment or testing situations.
Medium security is the default and opens most of the known ports for operation. This is important, because if a required service is blocked, then the system may not be able to network correctly. For example, if DNS were blocked, then the system would not be able to resolve the Fully Qualified Domain Name, or FQDN (such as the server www.linux.org), and therefore, would not be able to reach the Web site. The medium setting is the default because it opens these services.
The high security level blocks all but a few services, such as DNS, and really isolates the system. This level of security is most appropriate on a server where access is limited to only the services that the system provides. If a server provides FTP services, then perhaps only these services that provide FTP should be open. This will prevent attacks on another service from affecting the FTP server.
Firewall services are now set up during installation and usually use a screen, as shown in Figure 4-10, to enable the configuration of the firewall.