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Questions and Answers
ما هو نظام تشغيل لينكس؟
ما هو نظام تشغيل لينكس؟
لينكس هو نظام تشغيل متعدد المستخدمين.
ما هو دور سياسة أذونات الوصول في لينكس؟
ما هو دور سياسة أذونات الوصول في لينكس؟
تُستخدم سياسة أذونات الوصول لمنع الوصول غير المصرح به إلى الملفات والمجلدات.
ما هي أنواع أذونات الوصول الثلاثة التي تُمنح لكل ملف ومجلد في لينكس؟
ما هي أنواع أذونات الوصول الثلاثة التي تُمنح لكل ملف ومجلد في لينكس؟
ما هي أنواع المستخدمين في لينكس؟
ما هي أنواع المستخدمين في لينكس؟
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ما هو الغرض من المستخدم الفائق في لينكس؟
ما هو الغرض من المستخدم الفائق في لينكس؟
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ما هي أهمية المجموعات في نظام تشغيل لينكس؟
ما هي أهمية المجموعات في نظام تشغيل لينكس؟
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ما هي أنواع المجموعات في لينكس؟
ما هي أنواع المجموعات في لينكس؟
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ما هو الغرض من المجموعة الأساسية في لينكس؟
ما هو الغرض من المجموعة الأساسية في لينكس؟
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ما هي أنواع أذونات الوصول الثلاثة في لينكس؟
ما هي أنواع أذونات الوصول الثلاثة في لينكس؟
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ما هو مفهوم “”الوضع"” في لينكس؟
ما هو مفهوم “”الوضع"” في لينكس؟
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ما هو الغرض من الأمر chmod في لينكس؟
ما هو الغرض من الأمر chmod في لينكس؟
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Study Notes
Introduction to Operating Systems (SYST1)
- This course is part of the National School of Cybersecurity's (NSCS) 1st Year Basic Training in Cyber Security (1BT) program for 2024/2025.
- It's taught by Dr. Sassi Bentrad.
- The course covers Users, Groups and Permissions Management (10%).
Chapter 6: Users, Groups, and Permissions Management
- Linux is a multi-user operating system, meaning multiple users can use the computer simultaneously.
- Access permissions are needed for directories and files.
- Linux uses three access permissions for files and directories:
- Owner (User)
- Group
- Other
- Permissions are represented:
- read (r)
- write (w)
- execute (x)
- Absence of permission is denoted by a hyphen (-).
- Permissions can be viewed using numerical or symbolic notations.
- Different commands are used to manage users, groups, and permissions.
Owner Status
- There are three owner statuses:
- Owner: The user who created the file/directory.
- Owner Group: The primary group of the owner.
- Others: Users not in the owner group.
- Commands like
chown,chgrp, andchmodare used to manage owners, groups & permissions.
Permission (Access Mode)
- Permissions depend on the owner status.
- The
ls -lcommand with the-loption displays permission information for files and directories. - Permissions can be expressed numerically (octal) or symbolically.
Meaning of File Permissions
- Files are used to store data.
-
r(Read): View the contents. -
w(Write): Change the contents. -
x(Execute): Run the program or instructions for binary files.
Meaning of Directory Permissions
- Directories are used to store files and directories.
-
r(Read): View the directory contents (files and subdirectories). -
w(Write): Add, delete, or rename files within the directory -
x(Execute): enter the directory.
Superuser (Root User) vs. Normal User
- The superuser (root) has access to all system resources.
- Normal users have limited access based on permission settings.
-
sudois used to run commands with superuser privileges. - Different accounts (e.g.,
user_a,user_b) with varying permissions are part of a system.
sudo Command (Run Command with Superuser Privileges)
- The
sudocommand allows normal users to run commands with superuser privileges. -
sudoersare users with the necessary permissions to usesudo.
su (Switch User) Command
- The
sucommand is used to temporarily switch to another user, including the superuser (root).
useradd (Add User) Command
- Used to create new user accounts.
- Option
-mautomatically creates a home directory.
passwd (Set Password) Command
- Used to set up or change a user's password.
userdel (Delete User) Command
- Used to delete existing user accounts.
- Option
-ralso deletes the user's home directory.
Primary Group and Secondary Group
- Linux uses primary & secondary groups to manage user permissions.
- Primary group: the default group a user belongs to.
- Secondary group: additional group memberships for specified permissions
- Commands like
groupadd,usermod, andgpasswdmanage these groups.
groupadd (Add Group) Command
- Used to create new user groups.
usermod (Modify User Account Information)
- Used to modify a user's profile (including primary group, secondary groups, etc.) .
gpasswd (Add and Delete Users to Group) Command
- Used to add or remove users from groups.
- Supports password management for groups.
groupdel (Delete Group) Command
- Used to delete a group profile from the system.
chown (Change Owner of File and Directory) Command
- Used to change the ownership of files or directories.
chgrp (Change Group of File and Directory) Command
- Used to change the group ownership of files or directories
chmod (Change Access Mode) Command
- Used to modify the access permissions of files and directories.
- Symbolic and numerical methods are supported.
Check Current User Login Status (who and w command)
- Used for showing who's currently logged in and what they are doing.
id and groups (Check User ID and Group) Commands
- Used for checking the user ID and list of groups.
getent (Display User and Group Data) Command
- Retrieves data from system databases on users and groups.
chmod Command with Numbers
- Used to set permissions using numerical representations.
- The command uses octal numbers (base-8) representing permissions.
Extended access permissions
- Allows controlling access beyond basic
rwxpermissions. - Used for granular sharing control.
- SUID & SGID bits affect how programs are executed and permission control.
- Sticky bit is used in directories to restrict file renaming & deletion.
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Description
يتناول هذا الفصل إدارة المستخدمين والمجموعات في نظام التشغيل لينكس، حيث يمكن لمستخدمين متعددين استخدام الكمبيوتر في نفس الوقت. سيتم استعراض أذونات الوصول اللازمة للملفات والمجلدات، وكذلك كيفية إدارتها باستخدام أوامر معينة.
