Detailed explanation of HTML5 user and user group management commands under Linux

[Introduction] Sharing an operation document on permission management in Linux systems, let’s introduce the detailed explanation of Linux user and user group management commands. Friends in need can refer to this article. 1 The useradd useradd command can create a new user account. Its most basic usage is: usera

Share an operation document on permission management in the Linux system. Let’s introduce the Linux user and user group management commands. For detailed explanation, friends in need can refer to this article.

1. useradd

The useradd command can create a new user account. Its most basic usage is:

useradd username

For example, enter the following command :

useradd newuser

The system will create a new user newuser, and the user's Home directory is /home/newuser.

The useradd command has many parameters, and the commonly used combinations are:

useradd username-g group name-G group name-d Home directory name-p password

where :-g specifies the user's primary group

-G specifies the user's secondary group

-d specifies the user's Home directory

-p specifies the user's Password

For example, enter the following command:

useradd oracle –g oinstall –G dba –d /home/oracle –p ora123

The system will create a user oracle oracle user The primary group is oinstall, the secondary group is dba, the Home directory is /home/oracle, and the password is ora123.

2. userdel

The userdel command is used to delete an existing account. Its usage is:

userdel username

3. groupadd## The

#groupadd command can create a new user group. Its most basic usage is:

groupadd group name

For example, enter the following command:

groupadd newgroup

The system will create a new user group newgroup.

4. groupdel

The groupdel command is used to delete an existing user group. Its usage is:

groupdel group name

5. passwd

For system security reasons, each user in the Linux system has a corresponding user password in addition to its user name. Users can use the passwd command to change their password at any time. The general format of this command is:

passwd

After entering this command, enter the password and confirm the password in sequence according to the system prompts, and then the user password can be modified.

In addition, the super user can also modify the passwords of other users. The command is as follows:

passwd username

6. su

su command This command is very Importantly, it allows an ordinary user to have the permissions of a super user or other users, and it also allows a super user to do something as an ordinary user. Ordinary users must have the password of the superuser or other users when using this command. If you want to leave the current user identity, you can type the exit command. The general form of the su command is:

su – username

7. chmod

chmod command is very important , used to change the access permissions of files or directories. This command can be used in two ways: one is a literal setting method containing letters and operator expressions, and the other is a numeric setting method containing numbers.

Since the digital setting method is not very intuitive, this article will not introduce it. The usage of text setting method is as follows:

chmod [who] [+ | - | =] [mode] file name

The meaning of each option in the command is:

1. The operation object who can be any one of the following letters or their combination:

u means the user (user), that is, the owner of the file or directory

g means the same group ( group) users, that is, all users with the same group ID as the file owner

o means other (others) users

a means all (all) users, which is the system default value.

2. The operation symbols can be:

+ Add a certain permission

- Cancel a certain permission

= Grant the given permission and cancel other All permissions

3 mode Commonly used parameters indicating permissions are

r readable

w writable

x executable

Example :

1. Set the permissions of the file script to executable. The command is as follows:

chmod =rx text

After successful execution, use the ls -l script command to view the file attributes and the result is as follows:

-r-xr-xr-x 1 user group 0 Feb 10 09:42 script

2. Set the permissions of the file text to: readable, writable, and executable by the file owner, readable by users in the same group as the file owner, and others. Not readable by users. The command is as follows:

chmod u=rwx,g=r,o= text (note that there is no space after o= and there is a space after it)

After successful execution, use the ls –l text command to view The result of the file attributes is as follows:

-rwxr—– 1 user group 0 Feb 10 09:42 text

8. chown

chown is used to change a file or directory Owner and group, this command is also very commonly used. For example, the root user copies one of his files to the user oracle. In order to allow the user oracle to access the file, the root user should set the owner of the file to oracle, otherwise the user oracle cannot access the file. The basic usage of chown is:

chown [user:group] file

Example:

chown oracle:dba text

This command will The owner and group are changed to oracle and dba respectively.

The above is the detailed content of Detailed explanation of HTML5 user and user group management commands under Linux. For more information, please follow other related articles on the PHP Chinese website!