Linux details, linux details

Linux details, linux details

1. What is GPL, GNU, and free software?

GPL (General public license (GNU General public license): General public license. Generally, open-source software pursues license and allows anyone to edit software code, however, you also need to release your source code. Most software licenses are determined to deprive you of the freedom to share and modify the software. By contrast, the GNU General Public License attempts to ensure your freedom to share and modify free software. -- Ensure that free software is free for all users. GPL applies to software developed by the majority of Free Software Foundations and by authors who are obligated to use the software.

2. How do I select a Linux operating system version?

(1) If you only need a Linux desktop system and do not want to use pirated software, do not want to spend a lot of money to buy software, do not want to customize your own, or waste a lot of time on the system, you can select Ubuntu. That is: linux desktop, Ubuntu (2) is preferred. If you need a server-side Linux system or want to enter the enterprise for Linux O & M, you can choose Redhat or CentOS. That is: server system. The first choice is Redhat or CentOS (3). If you have high security requirements, you can select Debian or FreeBSD (4) if you need to use advanced database services and email network applications, you can select SUSE (many in Germany ). (5) If you are obsessed with the new technology experience or the latest version, you can use Fedora (a Redhat or Centos test yu release version ). (6) If you have a Chinese version, you can select the red flag. We choose Centos or Redhat.

3. How to partition a Linux operating system?

Linux requires at least two partitions:/and swap (1) Common partition/boot 100 Mswap 1.5 times -- do not exceed 16 GB/remaining hard disk size (2) database and storage database and storage of data resources we specify the size of/50--200G/data/remaining hard disk on the basis of regular partitions (3) portal website/50 -- 200 Gswap 1.5 times/boot M most of the remaining space is left out, Which partition will be used in the future, separate the partitions by yourself as needed * the following partitions are not required/usr/home/var

4. describes the Startup Process of Linux.

(1) Start Step 1-load BIOS when you turn on the computer power, the computer will first load BIOS information, BIOS information is so important that the computer must find it at the very beginning. This is because the BIOS contains CPU information, device startup sequence information, hard disk information, memory information, clock information, and PnP features. After that, the computer will be aware of which hardware device should be read. (2) Start Step 2-read MBR as we all know, the first sector of the 0th track on the hard disk is called MBR, that is, the Master Boot Record, that is, the Master Boot Record. Its size is 512 bytes, the pre-start information and partition table information are stored in the table. After the system finds the MBR of the hard disk specified by the BIOS, it will copy it to the physical memory where the 0 × 7c00 address is located. In fact, the content copied to the physical memory is the Boot Loader, and to your computer, it is lilo or grub. (3) Start Step 3-Boot LoaderBoot Loader is a small program that runs before the operating system kernel runs. Through this small program, we can initialize hardware devices and build a map of memory space to bring the system's hardware and software environment to a suitable state, in order to make all preparations for the final call to the operating system kernel. There are several Boot loaders, among which Grub, Lilo, and spfdisk are common loaders. Let's take Grub as an example. After all, there are not many people using lilo and spfdisk. The System reads grub configuration information (generally menu. lst or grub. lst) in the memory and starts different operating systems according to the configuration information. (4) Start Step 4: load the path of the kernel image set by grub. The system reads the memory image and decompress the image. At this time, the screen will usually output the "Uncompressing Linux" prompt. After the kernel is decompressed, the screen outputs "OK, booting the kernel ". The system places the decompressed kernel in the memory, and calls the start_kernel () function to start a series of initialization functions and initialize various devices to complete the establishment of the Linux core environment. So far, the Linux kernel has been established, and the Linux-based program should be able to run normally. (5) Step 5 of startup-after user-layer init is loaded Based on the inittab file, the first program to run is/sbin/init, the file reads the/etc/inittab file and initializes the file based on the file. In fact, the main function of the/etc/inittab file is to set the Linux running level. The setting format is ": id: 5: initdefault :", this indicates that Linux needs to run on level 5. The Linux operating level is set as follows: 0: shutdown 1: Single User Mode 2: multi-user mode without network support 3: multi-user mode with network support 4: reserved, not used 5: multi-user mode with network support and X-Window support 6: reboot the system, that is, restart the knowledge about the/etc/inittab file. In fact, there are still many (6) start step 6 -- init process to execute rc. after sysinit sets the running level, the first user-layer file executed by Linux is/etc/rc. d/rc. the sysinit script program does a lot of work, including setting PATH, setting network configuration (/etc/sysconfig/network), starting swap partitions, and setting/proc. If you are interested, you can go to/etc/rc. d. Check rc. in the sysinit file, the script is enough for you to watch (7) The seventh step of startup-start the kernel module based on/etc/modules. conf file or/etc/modules. d directory file to load the kernel module. (8) Start Step 8-execute scripts of different running levels. The system runs the corresponding scripts from rc0.d to rc6.d, to complete the initialization and start the corresponding service. (9) Start Step 9 -- execute/etc/rc. d/rc. local if you open This file, there is a sentence in it. after reading it, you will have a clear effect on This command: # This script will be executed * after * all the other init scripts. # You can put your own initialization stuff in here if you don't # want to do the full Sys V style init stuff. rc. local is the place for users to personalize Linux after all initialization work. You can put what you want to set and start here. (10) Start step 10-run the/bin/login program and enter the logon status. At this time, the system has entered the waiting time for the user to enter username and password, you can use your account to log on to the system. :) === The long start process is over, and everything is quiet... In fact, there are more complex underlying function calls behind this, waiting for you to study... This article even threw a brick and Jade :) this article referred to the following Articles, refined and made: http://bbs.chinaunix.net/thread-835918-1-1.htmlhttp://hi.baidu.com/fembed/blog/item/b9f0881f51145866f624e4be.htmlhttp://baike.baidu.com/view/9485.htm

5. Linux running level 0-6 Description

0 -- shutdown mode 1 -- single user mode (password for cracking day root) 2 -- Multi-user mode without network support 3 -- Multi-user mode with Network support (text mode, the most common mode in work) 4 -- retain, not use 5 -- X-windows with network support multi-user mode (desktop) 6 -- reboot the system, that is, start

6.32-bit and 64-bit system levels and how to choose

* 64-bit support for larger memory * 64-Bit Memory runs faster (both hardware and software must support 64-bit Support)