Roles of folders in the CentOS system

File structure in linux to see what each folder is for./bin binary executable command/dev special file/etc system management and configuration file/etc/rc. d. start the configuration file and script/home user main directory base point, such as the user

File structure in linux to see how each folder is used

/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/vmlinuz 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: The/bin directory contains the commands required for boot or common commands (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: The/sbin directory is similar to/bin. it 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. the/etc:/etc directory stores various system configuration files, including the user information file/etc/passwd and system initialization file/etc/rc. Linux runs normally only when these files exist. 4./root:/root directory is the root user directory. 5./lib:/lib 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 contains copies of the same subroutine, so that the executable files can be smaller and save space. 6. /lib/modules:/lib/modules Directory contains the system core which can be loaded with various modules, in particular, the modules required to reboot the system (such as network and file system drivers) when restoring damaged systems ). 7./dev:/dev 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/dev/mouse, just like accessing other files. 8./tmp:/tmp Directory stores information and data generated by the program during running. However, after boot, it is best to use/var/tmp to replace/tmp for running programs, because the former may have a larger disk space. 9./boot: the/boot directory stores the files used by the bootstrap loader, such as l I o. The core images are often stored 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:/mnt directory is the installation point of the system administrator temporary installation (mount) file system. 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 msdos file system, while/mnt/exta may be a soft drive using the ext2 file system, /mnt/cdrom optical drive and so on. 11./proc,/usr,/var,/home: installation point of other file systems.

 

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 man page 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. the domain name contains 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 setfdprm. 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 it does not indicate 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 information 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: "file" configuration file. It contains descriptions of different file formats. "file" is used to guess the file type. 9./etc/motd: motd 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. It is initialized by the script (scrui) 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 password software is installed. The shadow password file moves the encrypted password in the/etc/passwd file to the/etc/shadow file, which is only readable to the root user. This makes password deciphering more difficult to increase system security. 12./etc/login. defs: configuration file of the login command. 13./etc/printcap: similar to/etc/termcap, but for printers. Different syntaxes. 14./etc/profile,/etc/csh. login,/etc/csh. cshrc: files executed by B o u r n e or c shells upon logon 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 (root) to log on. Generally, only the Virtual Console is listed, so that it is impossible (at least difficult) to break into the system through a modem or network and obtain super user privileges. 16./etc/shells: list the shells that can be used. The chsh command allows you to change the logon shell within the specified range of 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. /Dev/makedev. 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/dev.

 

1./dev/console: the system console, that is, the monitor directly connected to the system. 2./dev/hd: ide hard drive interface. For example,/dev/hda indicates the first hard disk and had1 indicates the first partition of/dev/hda. If there are other hard disks in the system, they are/dev/hdb,/dev/hdc ,......; if multiple partitions exist, they are hda1 and hda2 ...... 3./dev/sd: scsi disk driver interface. If the system has a scsi hard disk, it will not access/dev/had, but/dev/sda. 4./dev/fd: Driver of the software drive device. For example,/dev/fd0 indicates the first floppy disk of the system, that is, a: Disk,/dev/fd1 indicates the second floppy disk ,...... the/dev/fd1h1440 indicates accessing 4 in drive 1. 5 High-density disks. 5./dev/st: scsi tape drive driver. 6./dev/tty: provides support for the Virtual Console. For example,/dev/tty1 indicates the first virtual console of the system, and/dev/tty2 indicates the second virtual console of the system. 7./dev/pty: supports remote logon to pseudo terminals. The/dev/pty device is required for telnet login. 8./dev/ttys: computer serial interface, which is the "com1" port for dos. 9./dev/cua: computer serial interface, used with the 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/dev/null.

 

/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 (distribution). locally installed programs and other things are under/usr/local, in this way, you do not need to re-install all programs when upgrading the new system or new release. Many contents in the/usr directory are optional, but these functions make the user use the system more effective. /Usr 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 of the xwindow system. To simplify the development and installation of x, x files are not integrated into the system. The xwindow system is a powerful graphic environment that provides a large number of graphic tool programs. If you are familiar with microsoft windows or machine learning, you will not feel helpless about the xwindow system. 2./usr/x386: similar to/usr/x11r6, but it is dedicated to x11 release 5. 3./usr/bin: collects almost all user commands, which are the system software libraries. Some other commands are in/bin or/usr/local/bin. 4./usr/sbin: contains unnecessary system management commands for the root file system, such as most service programs. 5./usr/man,/usr/info,/usr/doc: these directories contain all the manual pages, g n u information documents, and various other document files. Section of each online manual" There are two sub-directories. For example,/usr/man/man1 contains the source code of section 1 of the online manual (the original file is not formatted), and/usr/man/cat1 contains the formatted content of section 1. 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 site-wide 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: local software and other files are stored here. This is similar to/u s r. You may find some large software packages, such as tex and emacs.

 

/Var file system:/Var contains the data to be changed during normal running of the system. The directory size of the data is usually changed or expanded. Some contents in the original/var directory are in/usr, but to keep the/usr directory relatively stable, put those 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.

 

1./var/catman: contains the formatted help (man) page. The source file of the help page usually exists in/usr/man; some man pages may have pre-formatted versions, which exist in/usr/man/cat. Other man pages must be formatted when they are viewed for the first time. the formatted version exists in/var/man, so that other people do not have to wait for the same page to be formatted. (/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: stores 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 for storing the "false offline (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 requires a long time. Note that the system administrator may not allow/var/tmp to have very old files.

 

/Proc file system:/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 systems are described in more detail on the proc man page ).

1./proc/x: The Information Directory of process x. this x indicates the ID of the process. Each process has The Directory of the current process number. 2./proc/cpuinfo: stores information about the cpu, such as the cpu type, manufacturer, model, and performance. 3./proc/devices: List of device drivers with core configurations currently running. 4./proc/dma: displays the currently used d m a channel. 5./proc/filesystems: 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: current I/o port. 8./proc/kcore: physical memory image of the system. 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 syslog. 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 (swap ). 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 you want 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 starts. 17./proc/uptime: the duration of system startup. 18./proc/version: Core version.