Linux: Rute User's Tutorial and Exposition by Paul Sheer

Author:Paul Sheer
Language: eng
Format: mobi
Publisher: UNKNOWN
Published: 2018-06-16T23:00:00+00:00

newaliases whenever you modify the /etc/aliases file. In both cases, you must restart sendmail.

sendmail has received a large number of security alerts in its time. It is imperative that you install the latest version. Note that older versions of sendmail have configurations that allowed relaying by default—another reason to upgrade.

A useful resource to for finding out more tricks with sendmail is The Sendmail FAQ http://www.sendmail.org/faq/.

Chapter 31

lilo, initrd, and Booting

lilo stands for linux loader. LILO: is the prompt you first see after boot up, from which you can usually choose the OS you would like to boot and give certain boot options to the kernel. This chapter explains how to configure lilo and kernel boot options, and to get otherwise non-booting systems to boot.

The lilo package itself contains the files

§ ¤ /boot/boot.b /boot/message /sbin/lilo

/boot/chain.b /boot/os2_d.b /usr/bin/keytab-lilo

/usr/share/doc/lilo-<version>

¦ ¥

which is not that interesting, except to know that the technical and user documentation is there if hard-core details are needed.

31.1 Usage

When you first start your L INUX system, the LILO: prompt, at which you can enter boot options, is displayed. Pressing displays a list of things to type. The purpose is to allow the booting of different LINUX installations on the same machine, or different operating systems stored in different partitions on the same disk. Later, you can actually view the file /proc/cmdline to see what boot options (including default boot options) were used.

31.2.Theory 31.lilo ,initrd ,andBooting

31.2 Theory

31.2.1 Kernel boot sequence

A U NIX kernel, to be booted, must be loaded into memory from disk and be executed. The execution of the kernel causes it to uncompress itself and then run.&The word boot itself comes from the concept that a computer cannot begin executing without program code, and program code cannot get into memory without other program code—like trying to lift yourself up by your bootstraps, and hence the name. The first thing the kernel does after it runs is initialize various hardware devices. It then mounts the root file system on a specified partition. Once the root file system is mounted, the kernel executes /sbin/init to begin the UNIX operating system. This is how all UNIX systems begin life.

31.2.2 Master boot record

PCs begin life with a small program in the ROM BIOS that loads the very first sector of the disk into memory, called the boot sector of the master boot record or MBR. This piece of code is up to 512 bytes long and is expected to start the operating system. In the case of LINUX , the boot sector loads the file /boot/map, which contains a list of the precise location of the disk sectors that the LINUX kernel image (usually the file /boot/vmlinuz) spans. It loads each of these sectors, thus reconstructing the kernel image in memory. Then it jumps to the kernel to execute it.

You may ask how it is possible to load a file from a file system when the file system is not mounted. Further, the boot partition is a small and simple program and certainly does not support the many types of file systems and devices that the kernel image may reside in.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.