Linux System Users: Exploring the Secrets of Identity and Permissions

1. Linux system user overview

In the Linux architecture, users play a pivotal role. Each user has his or her own username and unique user ID for effective identification and permission control. Additionally, in addition to regular users, there is the privileged user root, which has the highest level of system access. A deep understanding of the user mechanism in the Linux environment is of great significance, both for system governance and security.

In the Linux operating system environment, we can detect user data that already exists in the system through the command line device. The following will explain in detail how to use various commands to query the status of various users in the Linux system.

2. View the /etc/passwd file

In the Linux operating system, vital user information is stored in the /etc/passwd file. Each line is the basic information of a user. The detailed contents of this file can be viewed through commands such as cat or less.

By consulting the /etc/passwd file, we can obtain the account name, user identifier (UID), group identifier (GID), and home directory path of each user in the systemlinux View system users, default terminal type and other details; these data play a key role in gaining insight into the users existing in the current system and their basic characteristics.

In addition, please pay attention to the matters in the /etc/passwd file. If a line begins with the "#" sign, it means that the content of this line has been commented out and is not recognized by the server as formal user account information.

3. Use the getent command to view users

Getent is a convenient tool for collecting database configuration data such as passwd and group. With it, we can obtain detailed information about all user accounts in the system, not just the content from the /etc/passwd file.

Using the getent passwd command and the pipe symbol combination, combined with the grep command, can achieve more detailed filtering and search operations, just like using getent passwd | grep "username" to query the account information corresponding to the specified user name.

Use the GETENT command to obtain more comprehensive system user information and implement diversified customized search and filtering functions.

4. View the current logged in user

In a Linux system environment, it is often necessary to know the user information currently connected to this system. You can use the 'who' or 'w' commands to query all users currently logged in to the system and their status.

With the `who` command, you will be able to know all the users currently connected to this terminal device, their login time and IP source; with the `w` command, you can obtain more detailed information, such as each user The instructions currently being run by the user, etc.

By monitoring the currently logged-in user information, abnormal conditions can be quickly detected, thereby improving the security of the entire system.

5. Use the id command to check the user identity

id command is used to reveal detailed identity information of a specified account or current user. With the help of the id command, you can learn key identity information such as the group, UID, and GID to which the current active user belongs.

In addition, the id command enables you to view certificate information associated with a user with a specific name, such as linux e-book, and use idusername to verify a user's authorization scope in the system.

The Id command, as an important tool for permission control and identity authentication, is widely used because of its simplicity and efficiency.

6. View processes under a specific user name

When you need to determine the status of a process running under a specific user name, you can use the ps command and its grep filter.

Use the PS tool (Ps) and its parameter -u to query all processes running under the specified account. Combined with the grep command, you can more accurately filter out the required process details.

By monitoring the process information of a specific user's execution environment, the usage of system resources can be effectively controlled and monitored.

7. View logged in history

In the Linux system, the system will automatically save the login and operation logs of each account in the /var/log/wtmp file.

Using the last command, you can easily check the recent network login and operation information of a specific or all users. This command has a detailed and comprehensive network login log query function, which can assist system administrators in accurately supervising and implementing account behavior audits.

In addition, the LastB command is used to display traces of login failures and help administrators quickly identify potential security risks.

8.Manage and add new users

In addition to accessing existing user data, in the Linux environment linux view system users, you must also frequently handle transactions related to new user accounts. The key processes include configuring user-related Management commands such as useradd, usermod, and userdel and their operations.

Use the useradd command to create a new user account, set the corresponding home directory path and default startup script (shell) and other parameters; use the usermod tool to adjust and change the attributes of existing accounts; finally, userdel is responsible for everything Completely delete selected user accounts residually.

Proper management of user accounts in a Linux system is one of the key links to ensure its security and stability. When adding new accounts, you should focus on setting appropriate permission levels and password policies.

9. User group management

In the Linux system, a key concept is user grouping, that is, each account can be associated with one or several groups to facilitate the common configuration of permissions and resource usage restrictions.

With the help of a series of utilities such as groupadd, groupmod and groupdel, we can efficiently implement group management in the Linux operating system. Ensuring that group permissions and their membership are set appropriately will have an extremely important impact on resource access control and permission allocation.

Understanding and properly applying the group concept of Linux system can not only improve the efficiency of management, but also ensure the level of security, and more effectively prevent sensitive data from illegal access.

10. Summary and Outlook

Through the above discussion, this article deeply analyzes the core elements of how to obtain and manage users in the Linux system environment and why the operation cannot be completed. From studying the important document /etc/passwd to using many command tools to perform diverse account information and status monitoring tasks, these steps have been explained in detail.

In-depth understanding and flexible use of these strategies can not only greatly improve the work efficiency of managers, but also enhance the protection of account security and stability in the Linux environment. With the advancement of science and technology and the expansion of demand, we have reason to believe that new methods and tools will emerge to further improve and enrich the current system.

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