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This article introduces the knowledge of "what are the common file management commands on the Linux system?" in the operation of actual cases, many people will encounter such a dilemma, and then let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

File View Class Command

1.cat

Cat can view the contents of a text file

Cat a.sh

-A View Line Terminator

Merge file contents cat / etc/fstab / etc/init.d/network > > / tmep/test.file

2.less/more

Files can be viewed page by page.

Less / etc/init.d/network

Pgup/pudn bhand f flips up / down

/ STRINT lookup string STRINT

N find next

3.head

The first n lines of viewing the file, the default is 10 lines

-n specify the first n lines head-11 / etc/init.d/network

4.tail

View the last n lines of the file. The default is 10 lines.

N lines after-n assignment, tail-11 / etc/init.d/network

Special usage

Tail-f / var/log/httpd/access_log continuously tracks the appended contents of files and is mainly used to view log files

Create files such as touch,vi,nano,nano, etc.

Delete the file rm-rf

Copy a file

1.cp

Cp source file target file

Only files can be copied, and one or more can be copied.

Cp / etc/init.d/network / etc/init.d/functions / tmp/

But if you copy multiple files, it can only be followed by a directory. If you copy a file, it can be followed by a file.

-f overwrite replication

-r copy the directory and all the files below

-a retain the original attributes when copying, such as ownership, 3D timestamp, mainly used for archiving documents

2.install

Install source target such as install / etc/grub2.cfg / tmp/

The default permission is 755 after copying. If the chmod command is lost, you can use scp to copy it from other hosts and then copy it with install, so you have the right to execute.

-m specify permissions install-m 000 / etc/grub2.cfg / tmp/

3. File lookup

Locate matches according to the database, fast, easy to use, non-internship

Find is copied by find command, so it is told in a separate article.

4. Move / rename full name file

Mv file to file2

Mv / etc/init.d/network / etc/init.d/network.bak

Mv / etc/init.d/network / tmp

5. Create a new directory

Mkdir-p cascading to establish a directory, skip if the directory already exists, and establish if it does not exist

Mkdir-pv / usr/local/tmp/src/httpd

6. Move / rename / delete just like a file

Second, use the command line expansion function to create / tmp/a1, / tmp/a2, / tmp/a1/a, / tmp/a1/b, and create a directory under the / tmp directory: xSecrety, xroomz, qroomy, qroomz

Mkdir-pv / tmp/a1 & & touch / tmp/a {1 / {arecine b}, 2}

Touch / tmp/ {x,q} _ {y,z}

How to modify the timestamp information of a file.

The data flow of a file is divided into two types, one is the file content, the other is the file metadata

There are thirteen metadata, 13 yuan for short, which is also the name of the rhyme of A Dream of Red Mansions.

1. File name

two。 File size

3. Data block where it is located

4.

5. File type

6. Inode where the file is located

7. Number of hard connections

8. Authority

9.UID

10.GID

11. Last visit timestamp

twelve。 The last time the contents of the file were changed

13. When the metadata was last changed

View file metadata stat file

Stat / dev/sr0

What if you change the file metadata?

Touch file changes the file with three timestamps

-an access, changing the access time, but also changing the time when the metadata was last changed

-m modify, change the time when the contents of the file were modified, but also change the time when the metadata was last changed

Create a file under the / tmp directory that starts with tfile, followed by the current date and time, with a file name such as: tfile-2016-05-27-09-32-22.

Copy all files or directories under the / etc directory that begin with p and end with non-numbers to the / tmp/mytest1 directory.

Mkdir-p / tmp/mytest1

Cp-r / etc/p* [^ [: digit:]] / tmp/mytest1

Create user tom, specify UID as 5001, home directory as / tmp/tom, shell as / bin/zsh, basic group as tom, and additional group as jack

Setenforce 0

Groupadd jack

What are the commonly used user and file management commands, and demonstrate the commands and usage.

What is a user? The user is the unique identification of the computer to the user.

Why should there be users? Because all processes can only be run by the user, the process that is not running is just a static file. No matter when and where only users can log on to the system and use computer resources.

The user format is as follows: separated by: no blank.

User name: X:UID:GID: comment: home directory: shell

Ajxzl:x:1000:1000:ajxzl:/home/ajxzl:/bin/bash

Slackware:x:1001:1001::/home/slackware:/bin/tcsh

User name: login name visible to the user

X: password. Placed in the / etc/shadow file. X is used to occupy seats.

UID: the unique identification that the computer can recognize. Same as GID: 0 is root.1-999 for system user. 1000-60000 ordinary users. 60000 reserved.

What is the system user? Because all processes must have an owner, that is, they must belong to a certain user. In order to enable some processes to boot or background processes, the assigned user is called the system user. These users can never log in to the system. Purely to run a process.

GID: user basic group.

Home directory: default directory when logging in

Shell: log in to shell by default

Useradd adds users.

Useradd [option] user name

Useradd ajxzl

-u UID useradd-u 3001 ajxzl2

-r system user useradd-r ajxzl3

-g GID basic group GID. But this group must have useradd-g 1000 ajxzl4 beforehand.

-G GID additional group GID, this group must have useradd-G 1001 ajxzl5 beforehand

-c comment useradd-c "This is a testusre" ajxzl6

-d directory user home directory. Useradd-d / tmp/ajxzl7 ajxzl7 default / home/USER_NAME

Home directory template file / etc/skel/

Modifying the contents of this directory will affect all new user home directory contents.

-s shell_name sets user shell. The default is / bin/bash. View all shell:cat / etc/shells

Where is the default shell set? / etc/default/useradd default options for new users

Useradd-s / bin/cash ajxzl8

-M does not create a home directory useradd-M ajxzl10

Note that-r will not create a home directory either.

User password management

Password management file: / etc/shadow in the following format: .man 5 shadow

Ajxzl9:$6 $/ DjwtprZ$sZ/Vw4d9.8hBGLkYCl7yaqMhKqXeIVAisTGVZ53o4v5AsY4HCSE0HqP5y7d2.K/FaaHzbuKTklXVrCMgbB3Bf.:17823:0:99999:7:::

User name: password after encryption: date of the last password change: minimum life of password: maximum password life: password warning period: password expiration time: account expiration time: reserved field

There are 9 fields in total.

User name: user login name

Password: password. Can be empty, which means no password. If it is * or! Indicates that login through password is prohibited.

Date of last password change:

Minimum password life: 0 means it is not set

Maximum useful life: 99999

Password disabled date: indicates the number of days after the warning period that the password has not been changed. At this point, login with a password will be prohibited, but it may be done in other ways.

Account ban period: login is prohibited.

Reserved field

Modify user: usermod [Action] username

-ag adds additional groups

-d home directory

-m modify the home directory and move the data to the new home directory

-L locks the user so that he cannot log in

-U unlock the user

Delete user userdel-r username

Passwd: command. Change user password

-d clear user password

Id command: viewing user information

-u only watch uid

-g only watch gid

-n results are displayed by name

Newgrp group_name switch user basic group

Finger displays user login information

Pwck: user items are checked according to / etc/passwd by default.

Correct number of fields

A unique and valid user name

A valid user and group identifier

Valid primary group

Valid home directory

A valid login shell pwck shadow checks whether the user's password is valid, expired, etc.

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