010-160 System Security & User Permissions 4 — Questions and Answers
Question 1: Which file contains the list of all groups on a Linux system?
- /etc/users
- /etc/group (Correct answer)
- /etc/shadow
- /etc/gshadow
Correct answer: /etc/group
/etc/group stores group definitions including group name, GID, and member list.
Question 2: A script has the SGID bit set. What happens when it executes?
- It runs with root privileges
- It runs with the privileges of the file's group owner (Correct answer)
- It runs with the calling user's primary group
- It prevents other users from executing it
Correct answer: It runs with the privileges of the file's group owner
The Set Group ID (SGID) bit causes execution with the file group's privileges rather than the caller's group.
Question 3: Which command is used to set an expiry date for a user's password?
- passwd -e
- usermod -e
- chage -E (Correct answer)
- chage -M
Correct answer: chage -E
`chage -E YYYY-MM-DD username` sets the date on which the account expires.
Question 4: What permission does 'r' grant on a directory?
- Allows creating files inside the directory
- Allows listing the directory's contents (Correct answer)
- Allows traversing into the directory
- Allows deleting the directory
Correct answer: Allows listing the directory's contents
Read permission on a directory allows listing its contents with `ls`.
Question 5: Which command would display the last time each user logged in?
- last
- lastb
- lastlog (Correct answer)
- who
Correct answer: lastlog
`lastlog` reads /var/log/lastlog and shows the most recent login time for every user account.
Question 6: What is the effect of running `chmod o-r file.txt`?
- Removes read permission from the owner
- Removes read permission from the group
- Removes read permission from others (Correct answer)
- Removes all permissions from the file
Correct answer: Removes read permission from others
In symbolic chmod syntax, 'o' means others, '-' removes, and 'r' is read permission.
Question 7: Which of the following best describes the principle of least privilege?
- Users should share accounts to minimize the number of accounts
- Users and processes should have only the minimum permissions needed for their tasks (Correct answer)
- The root user should perform all administrative work
- All files should be world-readable by default
Correct answer: Users and processes should have only the minimum permissions needed for their tasks
Least privilege limits access rights to the minimum necessary, reducing the attack surface.
010-160 System Security & User Permissions 4
Which file contains the list of all groups on a Linux system?