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Questions and Answers
What command is used to switch to another user account in a Linux system while obtaining their environment settings?
What command is used to switch to another user account in a Linux system while obtaining their environment settings?
What is a key risk associated with using the root account directly?
What is a key risk associated with using the root account directly?
What information does the 'who' command provide about users?
What information does the 'who' command provide about users?
What is the main purpose of creating groups in a system?
What is the main purpose of creating groups in a system?
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What is a consequence of creating GIDs under 1000?
What is a consequence of creating GIDs under 1000?
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Which command shows both local and network-based groups?
Which command shows both local and network-based groups?
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What does the command 'grep root /etc/group' accomplish?
What does the command 'grep root /etc/group' accomplish?
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Study Notes
Module 15: System and User Security
- Exam Objective 5.1 covers basic security and identifying user types on a Linux system.
- The objective focuses on various user types within a Linux environment.
Identifying User Accounts
- User accounts are designed to secure a Linux operating system.
- Accounts control file and directory access rights based on file permissions.
Users and Permissions
- User accounts belong to groups.
- This module covers commands to view user and group details and navigate between them.
Administrative Accounts
- Some commands require administrative or root privileges.
- Using the root account carries risks, so
sudoorsuare recommended for executing commands as root. - Risks of logging in as root:
- All processes run with root privileges.
- Easier to accidentally run non-admin tasks as root.
Switching Users
- The
sucommand allows running a shell as a different user. - The
sucommand with the[username]parameter opens a new shell. - After pressing Enter, the correct password for the target user is needed.
Executing Privileged Commands
- The
sudocommand enables executing commands as another user. - It's useful for distributions where root login isn't permitted.
- Unlike
su,sudoprompts for your own password. This prevents a possible compromise of root privileges.
User Accounts
- The
/etcdirectory contains files defining user and group accounts. - The
/etc/passwdfile provides user account information (name, password placeholder, UID, primary group ID, comment, home directory, shell). Fields are separated by colons.
Passwords
- The
/etc/shadowfile contains encrypted user passwords (access requires root privileges). - Fields in
/etc/shadowinclude username, encrypted password, last password change, minimum/maximum password age, warning before password expiry, inactive period and password expiry time.
System Accounts
- Users typically log in using regular accounts (UID > 1000).
- The root account has UID 0 and special access.
- System accounts (UID 1-499) manage services on the system.
- System accounts in
/etc/passwdand/etc/shadowmay have different fields (like home directory, shell, password).
Group Accounts
- Users can belong to one or more groups.
- The
/etc/passwdfile specifies the primary group membership. - The
/etc/groupfile defines additional or secondary group memberships. - Group information includes the group name, password holder(an 'x' indicates no password), group ID, and list of members in the group file.
Viewing User Accounts
- The
idcommand displays user and group information (UID, username, primary group, and details of other groups).
Viewing Current Users
-
The
whocommand lists currently logged-in users, their terminal, and login times. -
The
wcommand provides a more detailed view of logged-in users, including system status like user activity and load average.
Viewing Login History
- The
lastcommand displays login history, including previous and current login sessions. It gathers information from the/var/log/wtmpfile.
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Description
This quiz covers Module 15 of System and User Security, focusing on identifying user accounts and understanding the role of permissions in a Linux environment. It highlights different user types, including administrative accounts, and illustrates how to switch users while maintaining system security. Test your knowledge of Linux user management and permissions with this quiz.
