Linux basic commands

Linux command format:

COMMAND [OPTIONS ...] [ARGUMENTS ...]

Options: One or some of the features used to enable or disable commands;

Parameters: The Action object of the command, providing data to the command;

(1) LS

Displays a list of files under the specified path

ls [OPTION] ... [DIR] ...

-A,--all: Displays all files, including hidden files;

-L: Long format

-rw-r--r--1 root root 44800 14:32 Install.log

-rw-r--r--:

Leftmost first bit: file type

-, D, L, B, C, p, s

9 bits in the back: access rights, Perm

Number: The number of times a file has been hard-linked;

Left Root: Owner of File

Right root: Group of files

44800: Size of File

14 14:32: Last modified time for a file

Install.log: File name

-H,--human-readable: unit conversion

-D: Displays the relevant properties of the directory itself, usually with-l;

-R,--reverse: Reverse Display

-R,--recursive: recursive

Example: Working with the following command occasionally

View files in the/etc directory with the largest file size: ls-lhs/etc/| Head

View the latest several files in the/etc directory: ls-lt/etc/| head

(2) CD

Switch directories

CD or CD ~: Back to the current user's home directory

CD ~username: Switch to the home directory of the specified user

CD-: Switch back and forth between the previous directory and the current directory

(3) Type : query command Types

(4) TTY: View current terminal equipment

(5) Cat: File View command

(6) which: show the program file path of the command
which [OPTION] COMMAND

--skip-alias: Disable alias display

Locates the location of the executable file in the system.

(8) PWD: Current directory

(9) Echo: Echoing command

- N: Prevents the automatic addition of newline symbols;

- e: Allow the use of escape characters;

\\n: Line break

\\t: Tab

echo "$VAR _name": Variable is replaced , double quotation mark table weak reference

Echo ' $VAR _name ': variable does not replace , strong reference

Date: Display and set time

Date

Date [OPTION] ... [+format]: Display

Format: Formatting symbols

%d

%F

%T

Date [MMDDHHMM[[CC]YY][.SS]]: Set

MM: Monthly

DD: what date

hh: Hours

mm: minutes

YY: two-digit year

CCYY: four-bit year

. SS: Seconds

Example: View yesterday time: Date +%y%m%d-d '-1 day '

(11) Shut down the machine

Halt, Poweroff, shutdown, init 0

(12) Restart

Reboot, shutdown, init 6

(13) associated with user login

Who, WhoAmI, W

History: Command Histories

Environment variables:

Histsize: The number of records in the command history;

Histfile:~/.bash_history;

Histfilesize: The Order History file records the history of the number of bars;

History-d OFFSET

-C

History #: Shows the most recent # command in the past;

-A: Manually append the current session buffer's command history to the history file;

(mkdir): Create a directory

mkdir [Options]/path/to/somewhere

-P: exists in no error, and can automatically create the required directories;

-V: Show more information

-M MODE: Specify permissions directly when creating a directory;

(+) Tree:

-D: Show only directories

-L Level: Specifies the number of levels to display

-P Pattern: Displays only the path that is matched by the specified pattern;

(+) RmDir: Delete Empty directory

rmdir [OPTION] ... DIRECTORY ...

-V: Display process;

(18) View File Class command:

More

More [OPTIONS ...] FILE ...

-D: Show page flipping and exit tips

Less

Less [OPTIONS ...] FILE ...

Head

Head [OPTION] ... [FILE] ...

-C #: Specify get before # bytes

-N #: Specifies the first # line to get

-#：

Tail

tail [OPTION] ... [FILE] ...

-C #: Specifies the # bytes after fetching

-N #: Specifies the # line after fetch

-#：

-F: Trace displays the new content of the file;

Touch: Timestamp management tool for files

Touch [OPTION] ... FILE ...

-a:only Atime

-m:only Mtime

-T STAMP:

[[Cc]yy] MMDDHHMM[.SS]

-C: If the file does not exist, it is not created

() CP Copy command

Common options:

-I: Interactive

-R,-r: recursively copy directories and all internal content;

-A: archive, equivalent to-DR--preserv=all

-d:--no-dereference--preserv=links

--preserv[=attr_list]

Mode: Permissions

ownership: Belong to the main group

Timestamp:

Links

xattr

Context

All

-P:--preserv=mode,ownership,timestamp

-V:--verbose

-F:--force

MV: Moving, renaming files or directories

MV [OPTION] ... [-T] SOURCE DEST

MV [OPTION] ... SOURCE ... DIRECTORY

MV [OPTION] ...-t DIRECTORY SOURCE ...

Common options:

-I: Interactive

-F: Mandatory

RM: Delete command

RM [OPTION] ... FILE ...

Common options:

-I: Interactive

-F: Force delete

-R: Recursive

RM-RF

WC command: See how many lines or words are in the contents of a file

WC [OPTION] ... [FILE] ...

-l:lines

-w:words

-c:characters

Cut command: Cut file

Cut [OPTION] ... [FILE] ...

-D DELIMITER: Indicates delimiter

-F Fileds:

#: Section # Fields

#,#[,#]: Discrete multiple fields, such as 1,3,6

#-#: Multiple consecutive fields, such as 1-6

Mixed use: 1-3,7

--output-delimiter=string

Sort command: Text content sorting

Sort [OPTION] ... [FILE] ...

-F: Ignore character case

-R: Reverse order

-T DELIMITER: Field delimiter

-K #: Sort the specified fields as standard

-N: Sorting by numeric size

-u:uniq, sort after go heavy

(+) Uniq command: File content to go heavy

Uniq [OPTION] ... [FILE] ...

-C: Shows the number of repetitions of each line;

-D: Show only the rows that have been repeated;

-U: Displays only rows that have not been duplicated;

Note: Repeat for continuous and identical sides

Useradd: User-created

useradd [Options] LOGIN

-U UID: [Uid_min, Uid_max], defined in/etc/login.defs

-G GID: Indicates that the user belongs to the basic group, can be a group name, can also GID;

-C "COMMENT": User's comment information;

-d/path/to/home_dir: The home directory with the specified path;

-S Shell: Indicates the user's default shell program, the available list is in the/etc/shells file;

-G group1[,group2,... [, GROUPN]] : Specifies additional groups for the user, and the group must exist beforehand;

-r: Create a System user

CentOS 6:id<500< p= "" >

CentOS 7:id<1000< p= "" >

(groupadd): Group creation

Groupadd [OPTION] ... group_name

-G GID: Specifies the GID number; [Gid_min, Gid_max]

-r: Create a system group;

CentOS 6:id<500< p= "" >

CentOS 7:id<1000< p= "" >

ID: View user-related ID information

ID [OPTION] ... [USER]

-u:uid

-g:gid

-g:groups

-n:name

SU: Switch users or execute commands as other users

Su [Options ...] [-] [user [args ...]]

How to switch users:

Su UserName: Non-login switch, that is, the target user's configuration file will not be read;

Su-username: Login switch, will read the target user's configuration file; switch completely;

Note:root Su to other users do not need a password, non-root user needs a password when switching;

To change the identity of the execution command:

Su [-] username-c ' COMMAND '

Options:

-L: "Su-l UserName" equals "Su-username"

(+) Usermod: User attribute modification:

usermod [OPTION] Login

-U uid: New UID

-G GID: New Basic Group

-G group1[,group2,... [, GROUPN]] : The new add-on group, the original additional group will be overwritten, if the original, you want to use the-a option at the same time, indicating append;

-S shell: new default shell;

-C ' COMMENT ': new annotation information;

-D Home: New home directory, files in the original home directory will not be moved to the new home directory at the same time, to move, then use the-M option;

-L login_name: new name;

-l:lock the specified user

-u:unlock the specified user

-E YYYY-MM-DD: Indicates the user account expiration date;

-F INACTIVE: set inactivity period;

(+) passwd: add password to User

passwd [OPTIONS] UserName: Modify the password of the specified user, only the root user rights

passwd: Modify your password;

Common options:

-L: Lock the specified user

-U: Unlock the specified user

-N mindays: Specifying the shortest period of use

-X maxdays: Maximum lifespan

-W Warndays: How many days in advance to start warning

-I inactivedays: inactivity period;

--stdin: Receive user password from standard input;

echo "PASSWORD" | passwd--stdin USERNAME

Note:/dev/null, bit buckets

/dev/zero,

(userdel): Delete user

Userdel [OPTION] ... login

-r: Delete user home directory;

(GROUPMOD): Group Property Modification

Groupmod [OPTION] ... group

-N group_name: New name

-G GID: New Gid;

(+) Groupdel: Group Delete

(GPASSWD): group password

(PNS) Chage: Modify User Properties

chage [OPTION] ... LOGIN

-D Last_day

-E,--expiredate expire_date

-I.,--inactive inactive

-M,--mindays min_days

-M,--maxdays max_days

-W,--warndays Warn_days

(chmod): Modify file Permissions

chmod [OPTION] ... Octal-mode FILE ...

-R: Recursive Modify permissions

chmod [OPTION] ... Mode[,mode] ... FILE ...

MODE:

To modify all permissions for a class of users:

u=

g=

o=

ug=

A=

u=,g=

Modify one or some bit permissions for a class of users

u+

U-

chmod [OPTION] ...--reference=rfile FILE ...

Refer to the permissions of rfile file, change file to the same rfile;

(chown): Modify the owner of the file

chown [OPTION] ... [OWNER] [: [GROUP]] FILE ...

Usage:

OWNER

Owner:group

: GROUP

Note: The colon in the command is available. Replace;

-R: Recursive

chown [OPTION] ...--reference=rfile FILE ...

(CHGRP): Modify the genus Group of the file

CHGRP [OPTION] ... GROUP FILE ...

chgrp [OPTION] ...--reference=rfile FILE ...

Umask: Mask code when a file or directory is created

File:666-umask

Note: If there is an X permission in the result of a user with a class that has the permissions reduced, its permissions +1

Dir:777-umask

umask: View

umask #: Setting

Linux basic commands