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User-and-Group-Management.md

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User Management

What is a User Account?

A user account represents a user (e.g., employee) who uses the system regularly. Every person who is allowed to work on the computer must have a unique user account. Through this account, all activities and tasks of that person are recorded, and they are given the rights to work on the system.

User Account Facts

  • UID (User ID): Every user is assigned a unique UID (User ID), which helps to identify them in the system.
  • User Information: Information such as the user’s name, UID, home directory, and shell is stored in the /etc/passwd file.

Types of Users in Linux

  1. The Root User Account

    The Root user is the most powerful account in Linux. This account is created automatically during the system installation and has the highest level of privileges.

    • The Root user can perform any task, whether system administration or access any file or service.
    • This account should only be used for system administration and should not be used for everyday tasks.
    • The Root UID is always 0, and it cannot be deleted, but it can be disabled if needed.

  2. The Regular User Account

    This is a regular user account that is used by anyone who is allowed to work on the system.

    • A Regular user has moderate privileges, meaning they can only perform tasks for which they have been granted permission.
    • These accounts are used for routine work and can be disabled or deleted if needed.
    • UID typically starts from 1000 and can go up to 10000.

  3. The Service/System Accounts

    Service accounts are created to run services and processes on the system.

    • These accounts are not used for routine work.
    • Their UID usually ranges from 100 to 999.

User's Home Directory

  • Root User's Home Directory: The root user's home directory is /root.
  • Regular User's Home Directory: Every regular user has a home directory, which is typically /home/username. For example, if the user’s name is john, their home directory will be /home/john.

UID (User ID) in Detail

  • The Root User has a UID of 0.
  • A Regular User typically has a UID starting from 1000.
  • System Accounts have a UID between 100 and 999.

Files Related to Users and Groups

  1. /etc/passwd:
    This file contains information about all users, such as their username, UID, home directory, and shell. For example:

    john:x:1001:1001:John Doe:/home/john:/bin/bash

  2. /etc/group:
    This file contains information about all groups, such as the group name, GID (Group ID), and the users who are part of that group. For example:

    developers:x:1002:john,jane

Summary

  • User Accounts: Every person in Linux has a unique account, which gives them access to the system and tracks their activities.
  • Root User: This is the most powerful user, whose UID is always 0, and they can perform any task on the system.
  • Regular Users: These are normal user accounts with limited privileges, and their UID starts from 1000.
  • Service Accounts: These accounts are used for system services and have UIDs between 100 and 999.
  • Home Directories: Every user is given a home directory to store their personal files (e.g., /home/username).

Group Management

What is a Group in Linux?

A group is a collection of users that allows system administrators to manage users with similar permissions or access rights collectively. Instead of assigning permissions to individual users, the administrator can assign them to a group, and then apply those permissions or restrictions to the entire group.

A group is a collection of users that enables system administrators to apply similar permissions and restrictions to a set of users collectively. When multiple users require similar rights, they can be placed in a group, and then permissions related to those rights can be applied to the entire group.

Group Facts

  1. Users are assigned to a group
    Every user is assigned to at least one group to allow them similar permissions. A user can be a member of multiple groups.

  2. Each group has a unique Group ID (GID)
    Just like every user has a UID, every group is assigned a unique GID (Group ID), which identifies the group in the system.

  3. Group Information
    Group name, GID, and members (users) of the group are stored in the /etc/group file.

  4. Each user gets their own private group
    In Linux, each new user gets their own private group, which is named after the user. For example, if the user’s name is john, a group named john will be created for them.

  5. Users can belong to multiple groups
    A user can be a member of multiple groups. This allows the user to access controlled files and resources across various groups. For example, a user might be a member of both the "developers" and "testers" groups.

Where Group Information is Stored

  • /etc/group:
    This file stores all group information, such as the group name, GID, and the list of users in each group. Example: 
    developers:x:1002:alice,bob,john
    This means:
    • developers is the group name.
    • 1002 is the GID.
    • alice, bob, john are members of this group.