Basic knowledge about Linux
Users CRUD, rights management
First of all, we first learn how to learn how to view the user information in Linux:
id users: You can view the information of the user
Creating a user has five parts: four document rights management; configuration file required under / home users to copy already exists;
Its four managing user permissions are: / etc / passwd, / etc / group, / etc / shadow, / etc / gshadow four files;
Among them, we were to look at the contents inside look at these four files:
/etc/passwd
alex:x:1001:1001::/home/alex:/bin/bash
Username: Password (of course not stood here): User ID: Group ID: Remarks information: Path: the first command execution
/etc/group
alex:x:1001:
Group name: Password: Group ID: can add other users to this group (optional)
/etc/shadow
alex:.......:7::
Only to master the first two: Username: after encryption password: .......
/etc/gshadow
alex:!::
Group Name: Password (generally not set for when representatives did not!)
Mastered these basics, we need to learn to manage a user: useradd, usermod, userdel
Note: Linux General Command mode: command options parameters
useradd: add a user
usermod: Modify a User
Options:
-u: Specifies the user's UID
-g: Specifies the user group ID
-d: Specifies the home directory
-c: Alternate specified user information
-s: Specifies the user with shell
userdel: Delete User
-r: completely delete user
Tip: For the above things: useradd user
passwd user
Two instructions all use to create a user
userdel -r user
To completely delete a user
For the management group, we have three commands: groupadd, groupdel, groupmod
groupadd: Add a group
groupdel: delete a user
groupmod: modify a user
Optional parameters:
-g: group name modification
-n: name of the modified group
Rights management file, directory
Whether it is for file and directory, all files exist in the form of memory inside, which there is a rights management for different files under different user in Linux:
For purposes of the file: r (read), w (write), x (executable) is represented by these things
For purposes of Contents: r (read), w (create, delete, rename) x (enter switch)
For files and directories, it will include the following attributes:
Number of hard links permission information owner is a group of file size file creation time of the file name
-rw-------.
The first: a text message on behalf of
-: representatives plain text
d: is the target file type
l: soft links
b: block device file
p: pipe file
2-4: owner permissions ----> u
Permissions three categories: r read w write x execute
Bit 5-7: is a group of permissions -> g
Permission is above
8 - 10: Other users -> o
Ditto
Representatives are safety signs
User permissions to view:
ll: permission to view the current file directory
ll -d / home / alex /: View alex directory permissions
Add this: how to execute the file: ./ file path name
Permissions on the file / directory changes
chomd u = + rwx alex write directly to the file name or directory name to execute the action
chown modify the name of the owner and is a group of
chown root.root a.txt
Recursive changes owner and name is a group of
chown root.root {1....9}.txt
Modifies its catalog circulation as well as the following directories and files
chown -R lhf.lhf /test/
Add that: performing read and write to the above, we can also use the numbers represent: r = 4, w = 2, x = 1; how much added directly, then give u / g users like it.
>: Represents the contents of the left cover to the right of the file
>>: Represents the additional content on the left to the right
old cat file> new file
echo 'hello'> New File
two cat File> New File
Additional mention two instructions:
|: The contents of the previous output as input on behalf of the back of the input
wc -l file: Shows the number of lines in the file
File
tar -c (create) v (version) f (filename) test.tar plurality of files
Representative test.tar compressed files into a plurality of files and displaying compressed process
tar -t (View) f test.tar
View the contents of compressed files compressed behalf of
tar xvf filename specified path -C
Representative specific location unpack