Installation process for the Linux distribution CentOS series system

installation process for the Linux system CentOS release:

Boot boot process for kernel space:
POST (Power On Self Test)--bootsequence (BIOS) "MBR boot, sequential start phase bootsequence"-BootLoader (GRUB (stage1--stage1_5--stage2)) " Sequential boot "-kernel [INITRAMFS|INITRD] (devtmpfs,dev,proc,sys)" Kernel boot, device load "--switched-root (RO)" Perform root switch, virtual root switch to real roots, Store the device files in Ro "--/sbin/init (Centos5 is upstart init,centos7 in SysV init,centos6)" Turn on User space boot "- Graphical Interface System Installation Interface

The first-level subdirectories in the root file system in a CentOS system can be divided into two categories:
Normal first-level subdirectories of the root file system:
Absolutely no partitioning: Bin, Dev, Lib, lib64, sbin, usr (this is the CentOS 7 file system example)
Mount points for other file systems:
Can be a mount point directory: Boot, media, MNT, Proc, SYS, TMP, home, VAR

You can customize the mount point in the self-setting directory in the installation of the CentOS distribution Linux system, and you can customize the storage type selection:
/boot: basic disk partitioning;
/:LVM or raid
Swap: Basic disk partition or large file;
/HOME:LVM or raid
/VAR:LVM or raid
/USR:LVM or raid

In the system installation interface you need to plan the file system of various file storage path:
The path where all applications are stored;
The path where the runtime files that all applications depend on are stored;
The storage path of the configuration file used by all applications;
/sbin/init,/SBIN/SYSTEMD

System Installer Interface program for RHEL or CentOS systems: Anaconda

How the Anaconda works:
1. Interactive
TUI: Text manipulation interface based on curses; (Host memory < 512MB)
GUI: Graphical user interface; (host memory >= 512MB)
2. Unattended
With the help of KS configuration file implementation;
KS is all called Kickstart;

During the installation of the operating system, the system starts the process:
POST (Power On Self Test)-Bootloader (boot.cat--> isolinux.bin[isolinux.cfg]) "Boot loaded kernel file for hard drive"--Vmlinuz (initrd.img) "Virtual root "-Rootfs" root toggle "-Anaconda

Take the CD-ROM boot installation system For example, the installation process of the CentOS system:
1.POST
2. Read the mbr:isoliunux/boot.cat of the disc; Isolinux/isolinux.bin, its configuration file is: Isolinux/isolinux.cfg, its main content is:
Default VESAMENU.C32---What kind of C program to use to build menus;
Menu title Welcome to CentOS 6.7!------set the name of the title in the boot menu;
Label Linux--------tag name, which can be used to refer to all commands under it;
Menu label ^install or upgrade an existing system-----the content that is displayed in the boot menu, and the corresponding hotkey;
The menu default----------this label as the selected item in the menus, and the row must be unique throughout the file;
Kernel Vmlinuz-------------To specify the kernel file name for this boot;
Append initrd=initrd.img------------Additional parameters passed to the kernel command; common parameters are:
Initrd=initrd.img
Text: Start the installer from the text interface;
Askmethod: Manually select the method for installing packages and package groups:
Local disc, local hard disk
Network server: Ftp,http,nfs,cifs ...
Ip=ip_address
Netmask=netmask
Gateway=gateway
Dns=dns_srv_ip_address
Rescue: Enable emergency rescue mode;
Dd:device drivers, load additional drivers for the specified device, Br/>ks: Use Kickstart to start an unattended installation, specify the location of the KS configuration file with the KS parameter:
Local disc: Ks=cdrom:/path/to/kickstart_file
Local hard drive: Ks=hd:/device_name/path/to/kickstart_file
A Web site that is remote: ks=http://{host| ip}[:P Ort]/path/to/kickstart_file
One of the remote FTP sites: ks=ftp://[[email protected]]{hosr| ip}[:P Ort]/path/to/kickstart_file
3. Load the Rootfs and start the anaconda;

Anaconda also provides a command line interface with its pattern identifier:
Boot:linux text ip=1.1.1.1 netmas=255.255.255.0 gateway=1.1.1.127
Under the menu interface provided by Anaconda, press "ESC" key to enter the command line interface;

Note: All of the above procedures are performed on the boot device, and subsequent Anaconda and other packages and package groups that need to be installed are installed through the Yum plugin, so there is a Yum repository that can be accessed normally, and the location of the Yum repository can be in: local CD, Local hard disk, FTP server, HTTP server, NFS server, CIFS server

            在anaconda界面按"ESC"键以进行手动选择安装方式：            boot: linux askmethod

Anaconda's working process:
Pre-installation phase: Installation environment and planned configuration
1. The type of language used in the installation process;
2. keyboard layout type;
3. Target storage device installed by the system:
Basic Storage: Local Disk
Special Storage: Networked storage, Iscsi,nas, ...
4. Set host Name: Localhost.localdomain
5. Configure the network interface;
6. Select the time zone; Asia/shanghai
7. Super User password;
8. How to use the disk and the installation location of MBR;
9. Select the packages and package groups to install;

    安装阶段：            1.有可能运行一些安装前脚本，以完成初始化工作；            2.根据准备阶段规划的磁盘使用格式，进行分区或其他磁盘管理类的操作，而后执行格式化并安装指定的文件系统，然后再挂载所有的文件系统到指定的挂载点；            3.将选定的程序包或程序包组安装至指定的目录中；            4.安装bootloader(GRUB)至启动分区；            5.安装内核及initramfs；            6.有必要的话，可能会执行安装后脚本；    首次启动：            1.选择许可证信息；            2.创建普通用户账户；            3.配置内核的核心转储(Kdump, Kernel-Core dump)，如果内存小于2GB，Kdump不开启；            Kdump的作用：            如果某一时刻，内核核心崩溃，Kdump会将内核崩溃那一时刻内存中所有数据创建为一个映像文件并保存到磁盘上；事后通过分析此映像文件查找出内核崩溃的原因；            4.是否配置iptables防火墙和Selinux安全机制；建议初学者将此功能关闭；

This is the installation step for the approximate CentOS series system.

Installation process for the Linux distribution CentOS series system