/ etc File SystemThe/etc directory contains a variety of system configuration files, some of which are described below. Other you should know which program they belong to and read the program's M a n page. Many network configuration files are also in/etc.
1./ETC/RC or/etc/rc.d or/ETC/RC? D
A directory that starts, or alters, a script or script that runs at run-time.
2./etc/passwd
User database, where the domain gives the user name, real name, user start directory, encrypted password, and other information for the user.
3./ETC/FDPRM
A floppy disk parameter table that describes the different floppy disk formats. Can be set with SETFDPRM. See the help page for S e t f D p R m for more information.
4./etc/fstab
Specifies the list of file systems that need to be installed automatically at startup. Also includes information for the S W P zone enabled with Swapon-a.
5./etc/group
Similar to/etc/passwd, but not the user information but the group information. Includes various data for the group.
6./etc/inittab
The configuration file for init.
7./etc/issue
Includes the user's output information before the logon prompt. Usually includes a short description of the system or a welcome message. Specific content is determined by the system administrator.
8./etc/magic
"F i l E" configuration file. Contains a description of the different file formats, "F i l E" based on it guessing the file type.
9./ETC/MOTD
M o T D is the abbreviation for message of the day, and the user automatically outputs after successful login. The content is determined by the system administrator. Often used to advertise information, such as warnings for scheduled shutdown times.
Ten./etc/mtab
List of currently installed file systems. Initialized by the script (s C r i t p) and updated automatically by the Mount command. Used when a list of currently installed file systems is required (for example, the DF command).
/etc/shadow.
Shadow password file on a system with shadow (s h a d o W) password software installed. The shadow password file moves the encrypted password in the/E T c/p a s S W d file to the/E T C/s h a D o W, which is readable only by the superuser (R o o T). This makes it more difficult to decipher the password, which increases the security of the system.
/etc/login.defs.
L o The configuration file for the G i n command.
/etc/printcap.
Similar to/etc/termcap, but for printers. syntax is different.
/etc/profile,/E t/C/s H. L o g i n,/ETC/CSH.CSHRC
Files executed at login or start b o u r n E or C shells. This allows the system administrator to establish a global default environment for all users.
/etc/securetty.
Confirm the security terminal, that is, which terminal allows Superuser (r o o T) to log in. Only virtual consoles are generally listed, which makes it impossible (at least difficult) to break into the system via a modem (M o d e m) or network and gain superuser privileges.
/etc/shells.
Lists the S H e l l that can be used. The CHSH command allows the user to change the login's S H e L, within the scope specified in this file. A service process that provides a machine F T P service ftpd checks whether the user S H e l L is listed in the/etc/shells file, and if not, the user will not be allowed to log on.
/etc/termcap.
Terminal Performance database. Describes what "escape sequence" controls are used by different terminals. Instead of outputting the escape sequence directly (so that it works only with a particular brand of terminal), the program looks for the correct sequence of work to be done from/etc/termcap.
In this way, most programs can run on most terminals.
/ Dev File systemThe/dev directory includes device files for all devices. The device file is named with a specific convention, which is described in the device list. Device files are generated by the system during installation and can be described later with/dev/makedev. /d e v/m a k e d e v.local is a descriptive document written by the system administrator for local device files (or connections) (such as some non-standard device drivers that are not part of the standard Makedev). Below is a brief introduction/d e v Some of the commonly used files.
1./dev/console
The system console, which is the monitor directly connected to the system.
2./dev/hd
I d e hard drive driver interface. For example:/d e v/h D a refers to the first hard drive, and H a D 1 refers to the first partition of/d e v/h D a. If there are other hard disks in the system, then the/d e v/h D B,/d e v/h D C 、...... , if there are more than one partition, in turn, H D a 1, h D a 2 ...
3./DEV/SD
s C S I disk driver interface. If the system has s C s I hard drive, it will not be accessed/d e v/h a D, but access/d e v/s D a.
4./dev/fd
Floppy drive device driver. such as:/d e v/F D 0 refers to the system's first floppy disk, which is usually said 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 represents access to 1 in drive 4. 5 high-density disk.
5./dev/st
s C S I tape drive driver.
6./dev/tty
Provides Virtual Console support. such as:/d e v/t T y 1 refers to the system's first Virtual Console,/d e v/t T y 2 is the second Virtual Console of the system.
7./dev/pty
Provide remote login pseudo terminal support. The/d e v/p T y device is required to log in with Te L n e T.
8./dev/ttys
Computer serial interface, for D o S is the "C o M 1" port.
9./dev/cua
A computer serial interface, a device that is used with a modem.
Ten./dev/null
"Black hole," all the information written to the device disappears. For example: When you want to hide the output information on the screen, simply enter the output information into the/d e v/n u l L.
/ usr file system/usr is a very important directory, usually this file system is very large, because all programs are installed here. All files in/usr generally come from l i n u x release (d i s t r i b u t i o n); locally installed programs and other things under/usr/local, because this allows you to upgrade the new system or release without reinstalling all the programs. Many of the content in the/usr directory is optional, but these features make it more efficient for users to use the system. /U S R can accommodate many large packages and their configuration files. Some important directories are listed below (some of the less important directories have been omitted).
1./usr/x11r6
Contains all executable programs, configuration files, and supporting files for the x wi n d o w system. To simplify the development and installation of x, files for x are not integrated into the system. The x wi n d o W system is a powerful graphical environment that provides a large number of graphical tool programs. Users who are familiar with Microsoft WI n d o w s or m a c h i n t o S H will not be overwhelmed by the x wi n d o w system.
2./usr/x386
Similar/u s r/x 11r6, but is specifically for x one release 5.
3./usr/bin
Centralized almost all user commands, is the software library of the system. Some other commands are in/bin or/usr/local/bin.
4./usr/sbin
Includes unnecessary system administration 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 manual pages, G-N u information documents, and various other document files. Each online manual has two subdirectories for the section. For example:/u S r/m a n/m a N 1 contains the source code for the first section of the online manual (no formatted original file),/U S r/m a n/c a T 1 contains the first section of the formatted content. The online manual is divided into the following nine sections: internal commands, system calls, library functions, devices, file formats, games, macro packages, System management, and core programs.
6./usr/include
Contains the header files of the C language, which are many. H ends with a description of the data structure, sub-procedures, and constants used in the C language program. In order to maintain consistency, this should actually be placed under the/usr/lib, but it is customary to use the name
Word.
7./usr/lib
Contains the immutable data file for the program or subsystem, including some s i t e-w i d e configuration files. The name L I b originates from the library; The original library of programming also exists in/usr/lib. When the program is compiled, the program connects to the library. There are also a number of programs that store configuration files.
8./usr/local
Locally installed software and other files are placed here. This is very similar to/U S R. Users may find some of the larger packages, such as T e X, E m a C s, and so on.
/ var file system/var contains data to be changed when the system is generally running. Usually the size of the directory in which the data resides is constantly changing or expanding. Some of the original/V a R catalog is in/U S R, but in order to maintain the relative stability of the/U S R directory, the directories that require frequent changes are placed in/V a R. Each system is specific, i.e. it is not shared with other computers over the network.
Some important directories are listed below (some of the less important directories are omitted).
1./var/catman
The formatted Help (m a N) page is included. The source file of the help page is generally present/U s r/m a n/m a n; some m a n pages may have a pre-formatted version, present/U S r/m a n/c a T. While the other M-N pages need to be formatted for the first time, the formatted version exists in/var/man, so that other people can look at the same page without waiting for formatting. (/var/catman are often cleared, just as you would clear a temporary directory.) )
2./var/lib
The file to be changed when the system is in normal operation.
3./var/local
Variable data that holds the programs installed in the/usr/local (that is, programs installed by the system administrator). Note that if necessary, even locally installed programs will use other/var directories, such as/var/lock.
4./var/lock
Lock the file. Many programs follow the convention of creating a locked file in/var/lock to support their use of a particular device or file. When other programs notice this lock file, you will no longer use this device or
Thing
5./var/log
Log of various programs (L o g) files, especially logins (/var/log/wtmp log records all to system login and logoff) and Syslog (/var/log/messages Records store all core and System program information). The files in the/var/log often grow in uncertainty and should be cleaned up regularly.
6./var/run
Save the information file about the system that is valid before the next system boot. For example,/var/run/utmp contains information about the user who is currently logged on.
7./var/spool
directory where the "spool (s P o L)" program is placed, such as M a I l, n e w s, print queue, and other queue working directory. Each of the different s P o L has its own subdirectory under/var/spool, for example, the user's mailbox is stored in the/var/spool/mail.
8./var/tmp
Temporary files that are larger or require a longer time than/TMP are allowed. Note system administrators may not allow/var/tmp to have very old files.
/proc File SystemThe/proc file system is a pseudo file system, which means that it is a directory that does not actually exist, so this is a very special directory. It does not exist on a disk, but is generated in memory by the core. This directory is used to raise
Information about the system. Here are some of the most important files and directories (the/proc file system is described in more detail in the proc man page).
1./proc/x
For the information directory of process X, this x is the identification number of this process. Each process has a directory called its own process number under/proc.
2./proc/cpuinfo
Information about the processor (C p u), such as the type of C p u, manufacturer, model, and performance.
3./proc/devices
A list of device drivers for the currently running core configuration.
4./PROC/DMA
Displays the D m a channel currently in use.
5./proc/filesystems
The file system information for the core configuration.
6./proc/interrupts
Displays the information about the interrupt information and occupants that were occupied, and the amount that was consumed.
7./proc/ioports
The I/O port currently in use.
8./proc/kcore
System physical memory image. It is exactly the same size as the physical memory, but it does not actually occupy so much memory; it is only created when the program accesses it. (Note: Unless you copy it to a place,/proc does not have any
Anything that takes up any disk space. )
9./proc/kmsg
The message for the core output. will also be sent to S Y S l o G.
Ten./proc/ksyms
The core symbol table.
/proc/loadavg.
System "average load"; 3 meaningless indicators indicate the current workload of the system.
/proc/meminfo.
Various memory usage information, including physical memory and swap partition (s w a P).
/proc/modules.
Stores which core module information is currently loaded.
/proc/net.
Network protocol status information.
/proc/self.
A symbolic connection to the process directory that holds the program to view/proc. When 2 processes view/proc, this will be a different connection. This is primarily convenient for the program to get its own process directory.
/proc/stat.
The different states of the system, for example, the number of times a page error occurred after the system started.
/proc/uptime.
The length of time the system started.
/proc/version.
Core version.
Introduction to the file structure of Linux
