CentOS system folder

/Bin binary executable command/dev device Special file/etc system management and configuration file/etc/rc. d. start the configuration file and script/home user home directory base point. for example, if the user's home directory is/home/user, you can use ~ User represents the/lib standard programming library, also known as the dynamic link shared library, which is similar to the. dll file in windows.

/Bin binary executable command
/Dev special file
/Etc system management and configuration file
Configuration files and scripts started by/etc/rc. d
The base point of the/home user's home directory. for example, if the user's home directory is/home/user, you can use ~ User
/Lib standard programming library, also known as dynamic link shared library, works similar to. dll files in windows
/Sbin System Management Command, which stores the management program used by the system administrator.
/Tmp public temporary file storage point
/Root system administrator's home directory (haha, privileged class)
/The mnt system provides this directory for users to temporarily mount other file systems.
The/lost + found directory is usually empty, and the system shuts down abnormally, leaving the "homeless" file (what is. chk in windows) here
/Proc virtual directory, which is the ing of system memory. You can directly access this directory to obtain system information.
/Var overflow of some large files, such as log files of various services
The/usr directory contains almost all the applications and files to be used. Including:
/Usr/X11R6 directory for storing X Windows
/Usr/bin numerous applications
/Usr/sbin hyperuser management program
/Usr/doc linux document
Header files required for developing and compiling applications in/usr/include linux
/Usr/lib common dynamic link library and software package configuration file
/Usr/man help document
/Usr/src source code. the linux kernel source code is stored in/usr/src/linux.
/Usr/local/bin commands added locally
/Usr/local/lib: locally added Library

Generally, the space occupied by the root file system should be relatively small, because most of the files do not need to be changed frequently, it also includes strict files and a small, infrequently changed file system that is not easily damaged. Except for a possible/v m l I n u z standard system boot image, the root directory generally does not contain any files. All other files are in the subdirectory of the root file system.
1./bin directory
The/B I n directory contains commands required for boot or commands that common users may use (possibly after boot ). These commands are executable programs of binary files (B I n is short for B I n a r y--binary). most of them are important system files in the system.
2./sbin Directory
The/s B I n directory is similar to/bin and is also used to store binary files. Most of these files are the basic system programs used by the system administrator. although common users can use them when necessary, they are generally not used by common users.
3./etc directory
The/e t c Directory stores various system configuration files, including user information files/e t c/p a s w d, system initialization file/e t c/r c. L I n u x relies on these files for normal operation.
4./root directory
The/root directory is the root user directory.
5./lib Directory
The/l I B Directory is the shared library required by the program on the root file system. it stores the shared files required by the root file system program. These files contain code that can be shared by many programs, so that each program does not contain copies of the same subroutine, so the executable file can be smaller and save space.
6./lib/modules Directory
The/lib/modules Directory contains the system core which can be loaded with various modules, especially those required to reboot the system (such as network and file system drivers) when restoring the damaged system ).
7./dev directory
The/d e v Directory stores the device files, that is, the device driver. you can use these files to access external devices. For example, you can access the mouse input by accessing/d e v/m o u s e, just like accessing other files.
8./tmp Directory
The/tmp Directory stores information and data generated by the program during runtime. However, after boot, it is best to use/v a r/t m p to replace/tmp for the running program, because the former may have a larger disk space.
9./boot directory
The/B o t Directory stores the files used by the bootstrap loader, such as l I L O. The core image is often put here, rather than in the root directory. However, if there are many core images, this directory may become very large, and it would be better to use a separate file system. Note that the core image must be in the first 1 0 2 4 cylinder of the I D E hard drive.
10./mnt Directory
The/m n t directory is the installation point for the temporary installation (m o u n t) file system by the system administrator. The program does not automatically support installation to/mnt. /Mnt can be divided into many sub-directories. for example,/mnt/dosa may be a soft drive using the m s d o s file system, the/mnt/exta may be a soft drive using the e x t 2 file system, or a/mnt/cdrom optical drive.
11./proc,/usr,/var,/home directory
Other file system installation points.

The following details

/Etc file system
The/etc directory contains various system configuration files, which are described below. Others you should know which program they belong to and read the m a n pages of the program. Many network configuration files are also in/etc.
1./etc/rc or/etc/rc. d or/etc/rc ?. D
The Directory of scripts or scripts that start or change at the running level.
2./etc/passwd
User database, where the domain provides the user name, real name, user start Directory, encrypted password, and other user information.
3./etc/fdprm
Floppy disk parameter table to describe different floppy disk formats. Setfdprm can be used for setting. For more information, see the help page of s e t f d p r m.
4./etc/fstab
Specifies the list of file systems to be automatically installed at startup. It also contains information about the s w a p zone enabled with swapon-.
5./etc/group
Similar to/etc/passwd, but not user information but group information. Including various data of the group.
6./etc/inittab
Init configuration file.
7./etc/issue
Including the user's output before the logon prompt. It usually includes a short description or welcome information of the system. The specific content is determined by the system administrator.
8./etc/magic
"F I l e" configuration file. Contains descriptions of different file formats. "f I l e" is based on the file type.
9./etc/motd
M o t d is short for Message Of The Day, which is automatically output after The user logs on successfully. The content is determined by the system administrator. It is often used for notification information, such as warning about the scheduled shutdown time.
10./etc/mtab
List of currently installed file systems. Initiated by the script (s c r I t p) and automatically updated by the mount command. Use (such as the df command) when you need a list of currently installed file systems ).
11./etc/shadow
The shadow password file on the system where the shadow (s h a d o w) Password software is installed. In the shadow password file, move the encrypted password in the/e t c/p a s w d file to/e t c/s h a d o w, the latter is only readable to super users (r o t. This makes password deciphering more difficult to increase system security.
12./etc/login. defs
L o g I n command configuration file.
13./etc/printcap
Similar to/etc/termcap, but for printers. Different syntaxes.
14./etc/profile,/e t c/c s h. l o g I n,/etc/csh. cshrc
Files executed by B o u r n e or C shells at login or startup. This allows the system administrator to create a global default environment for all users.
15./etc/securetty
Confirm the security terminal, that is, the terminal that allows the super user (r o t) to log on. Generally, only the Virtual Console is listed, so it is impossible (at least difficult) to break into the system through a modem (m o d e m) or network and obtain the super user privilege.
16./etc/shells
List the available s h e l. The chsh command allows you to change the logon s h e l within the range specified in this file. The ftpd service process that provides a machine f t p service checks whether the user s h e l is listed in the/etc/shells file. if not, the user is not allowed to log on.
17./etc/termcap
Terminal Performance Database. Describes the escape sequence used by different terminals. When writing a program, the escape sequence is not output directly (this can only work on terminals of a specific brand), but the correct sequence of the work to be done is searched from/etc/termcap. In this way, most programs can run on most terminals.


/Dev file system
The/dev directory contains the device files of all devices. Device files are named according to specific conventions, which are described in the device list. The device files are generated by the system during installation and can be described in/dev/MAKEDEV later. /D e v/m a k e d e v. local is the description document written by the system administrator for the local device file (or connection) (for example, some non-standard device drivers are not part of the standard MAKEDEV ). The following describes some common files in/d e v.
1./dev/console
The system console, that is, the Monitor that connects directly to the system.
2./dev/hd
I D E hard drive interface. For example,/d e v/h d a refers to the first hard disk, and h a d 1 refers to the First Partition of/d e v/h d. If there are other hard disks in the system, they are/d e v/h d B,/d e v/h d c ,......; if multiple partitions exist, they are h d a 1, h d a 2 ......
3./dev/sd
S c s I disk driver interface. If the system has a s c s I hard disk, it will not access/d e v/h a d, but/d e v/s d.
4./dev/fd
The driver of the drive. For example,/d e v/f d 0 indicates the first floppy disk of the system, which is usually referred to as A: disk,
/D e v/f d 1 refers to the second floppy disk ,...... the/d e v/f d 1 H 1 4 4 0 indicates accessing 4 in drive 1. 5 High-density disks.
5./dev/st
S c s I tape drive driver.
6./dev/tty
Supports the Virtual Console. For example,/d e v/t y 1 indicates the first virtual console of the system, and/d e v/t y 2 indicates the second virtual console of the system.
7./dev/pty
Supports remote logon to pseudo terminals. You must use the/d e v/p t y device when logging on to Te l n e t.
8./dev/ttys
The computer serial interface is the "c o m 1" port for d o s.
9./dev/cua
Computer serial interface, a device used with a modem.
10./dev/null
"Black Hole", all information written to this device will disappear. For example, to hide the output information on the screen, you only need to input the output information to/d e v/n u l.

/Usr file system
/Usr is a very important Directory. usually this file system is large because all programs are installed here. /All files in usr are generally from the L I n u x release (d I s t r I B u t I o n ); locally installed programs and other things are stored in/usr/local, because you do not need to re-install all programs when upgrading the new system or release version. Many contents in the/usr directory are optional, but these functions make the user use the system more effective. /U s r can accommodate many large software packages and their configuration files. Some important directories are listed below (some less important directories are omitted ).
1./usr/X11R6
Contains all executable programs, configuration files, and support files for the X Wi n o w system. To simplify the development and installation of X, X files are not integrated into the system. X Wi n d o w system is a powerful graphics environment that provides a large number of graphics tool programs. If you are familiar with Microsoft Wi n d o w s or M a c h I n o s h, you will not feel helpless about X Wi n d o w system.
2./usr/X386
Similar to/u s r/X 11R6, but it is dedicated to X 11 Release 5.
3./usr/bin
A collection of almost all user commands is a software library of the system. Some other commands are in/bin or/usr/local/bin.
4./usr/sbin
Includes unnecessary system management commands for the root file system, such as most service programs.
5./usr/man,/u s r/I n f o,/u s r/d o c
These directories contain all the manual pages, g n u information documents, and various other document files. Each "section" of an online manual has two sub-directories. For example,/u s r/m a n 1 contains the source code of section 1 of the online manual (the original file is not formatted ), /u s r/m a n/c a t 1 contains the first formatted content. L The online manual is divided into nine sections: internal commands, system calls, library functions, devices, file formats, games, macro software packages, system management, and core programs.
6./usr/include
Contains the header file of C language. these files end with. h and are used to describe the data structures, subprocesses, and constants used in C language programs. In order to maintain consistency, this should be put under/usr/lib, but this name has always been used.
7./usr/lib
Contains unchanged data files of programs or subsystems, including some s I t e-w I d e configuration files. The name l I B is from the library. The original library for programming also exists in/usr/lib. When you compile a program, the program will be connected to the library. Many programs store configuration files.
8./usr/local
Install the software and other files locally. This is similar to/u s r. You may find some large software packages, such as t e x and E m a c s.


/Var file system
/Var contains the data to be changed during normal operation of the system. The directory size of the data is usually changed or expanded. In the original/v a r Directory, some contents are in/u s r, but to keep the/u s r directory relatively stable, put the directories that need to be changed frequently in/v a r. Each system is specific, that is, it is not shared with other computers through the network.
Some important directories are listed below (some less important directories are omitted ).
1./var/catman
Contains the formatted help (m a n) page. The source file of the help page usually exists in/u s r/m a n. some m a n pages may have pre-formatted versions, exist in/u s r/m a n/c a t. Other m a n pages must be formatted when they are viewed for the first time. the formatted version exists in/var/man, so that others do not have to wait for formatting when looking at the same page. (/Var/catman is often cleared, just like clearing a temporary directory .)
2./var/lib
Stores the files to be changed when the system is running normally.
3./var/local
Store variable data of programs installed in/usr/local (that is, programs installed by the system administrator ). Note: If necessary, other/var directories, such as/var/lock, will be used even for locally installed programs.
4./var/lock
Lock the file. Many programs follow the convention of generating a locked file in/var/lock to support the use of a specific device or file. Other programs will no longer use this device or file when they notice this locked file.
5./var/log
Logs of various programs (L o g), especially login (/var/log/wtmp log records all logon and logout to the system) and syslog (/var/log/messages records store all core and System program information ). Files in/var/log often grow uncertain and should be cleared regularly.
6./var/run
Save the system information files that are valid before the next system boot. For example,/var/run/utmp contains the information of the user Currently logged on.
7./var/spool
Directory of the "s p o l" program, such as the directory where m a I l, n e w s, print queue and other queues work. Each different s p o l has its own subdirectory under/var/spool. for example, the user's mailbox is stored in/var/spool/mail.
8./var/tmp
A temporary file that is larger than/tmp or needs to exist for a long time. Note that the system administrator may not allow/var/tmp to have very old files.


/Proc file system
The/proc file system is a pseudo file system, that is, it is a directory that actually does not exist, so this is a very special Directory. It does not exist on a disk, but is generated by the core in the memory. This directory is used to provide information about the system. The following describes some of the most important files and directories (/proc file system has more details on the proc man page
).
1./proc/X
The information directory of process X indicates the ID of the process. Each process has a directory named its own process number under/proc.
2./proc/cpuinfo
Stores information about the processor (c p u), such as the type, manufacturer, model, and performance of the c p u.
3./proc/devices
List of device drivers of the core configurations currently running.
4./proc/dma
Displays the currently used d m a channel.
5./proc/filesystems
The file system information of the core configuration.
6./proc/interrupts
Displays the information of the interrupted and occupied users, and the number of occupied users.
7./proc/ioports
The currently used I/O port.
8./proc/kcore
System physical memory image. It is identical to the physical memory size, but it does not actually occupy so much memory; it is created only when the program accesses it. (Note: Unless you copy it to somewhere, nothing in/proc occupies any disk space .)
9./proc/kmsg
Core output message. It will also be sent to s y s l o g.
10./proc/ksyms
Core symbol table.
11./proc/loadavg
System "average load"; three meaningless indicators indicate the current workload of the system.
12./proc/meminfo
Various memory usage information, including physical memory and swap partition (s w a p ).
13./proc/modules
Stores information about the core modules currently loaded.
14./proc/net
Network Protocol status information.
15./proc/self
Stores the symbolic connection to the process Directory of the program to view/proc. When two processes View/proc, this will be a different connection. This allows the program to obtain its own process directory.
16./proc/stat
Different states of the system, such as the number of page errors after the system is started.
17./proc/uptime
The duration of system startup.
18./proc/version
Core version.