Linux system learning series-Memorandum

1, Foreword ---- preface
I have been operating Linux in the office and understand a lot, but it is not a system, and many basic things are still unfamiliar, therefore, I wrote the Article in this series to make a system review and memo. Although I have this idea, I have never implemented it, I don't know where to start, so I decided to write a part first and then adjust the sequence.
current ideas: linux overview --- File System Structure ---- Startup Process ----- kernel introduction ---- common command set ---- supplement

2. Linux ---- Overview
We can see the origins of Linux and the development history of Unix systems. At present, we often see several major "genres": Boss-Microsoft win; Western Region genre-MAC; Wudang-Linux; shaolin ---- UNIX;
Here, Linux is a kernel, a single kernel, and the kernel is loaded into the memory as a whole. What we see is the release version. It is a collection of Kernel plus various GNU software, including the desktop environment.
Many releases do not describe in detail. If you want to use KDE for beautiful desktops, you can simply use gnome.

The idea of Linux is that everything is regarded as a file!

 

3. Linux-File System Structure

3.1 partitions
Here, let's take a look at the partition, which is divided into the primary partition and the extended partition. Linux has a maximum of four partitions, and the extended partition is more of a container or concept, which is divided into logical partitions, logical partitions are atomic and cannot be partitioned by molecules. Different from win series, Linux maps physical addresses in sub-directories first, this is why it can mount directories to different partitions.
Now we can see the following figure in detail.

3.2 Linux File System Type
After partitioning, you will be faced with the choice of the file system type. This is a bit of a detour, that is, the well-known nfts, FAT32, and so on. It mainly defines the storage mode of files on disks, such as the cluster size, how to allocate file space.

Common File Systems:

Ext2: an upgraded version of ext3: ext2, commonly used file system in early Linux, with the log function ramfs: memory file system, fast NFS: Network File System, invented by Sun, mainly used for remote file sharing MS-DOS: MS-DOS File System vfat: Windows 95/98 operating system using the file system fat: Windows XP operating system using the file system NTFS: windows NT/XP File System HPFs: OS/2 file system proc: Virtual process File System iso9660: File System ufssun used by most CDS: OS file system ncpfs: file system used by the Novell Server smbfs: Samba shared file system XFS: an advanced Log File System developed by SGI, supporting ultra-large file JFS: the log file system reiserfs used by ibm aix: File System UDF Based on the Balance Tree Structure: erasable data disc File System
 

 
3.3 file structure
We know that there are many folders under the root directory of the system. What are the purposes of these folders in Linux? I found a good graph on the Internet. For more information, see, however, this figure is a bit old. For the current Ubuntu release, there is also a directory, that is, the run directory. For centos, there may be SELinux directories and so on.
Figure: