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Summary
Security is a central concern of the system administrator. In this chapter, you have learned the basic concepts and practices of system security. The tools introduced will be useful when attempting to secure a system connected to the Internet.
Questions
1. | Which of the following files do not need to be owned by a user?
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2. | Which of the following printouts represents a possible output from the id command?
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3. | What is the UID of the superuser?
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4. | Name one restriction placed on the root account?
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5. | Name the default permissions mask set in the user’s shell?
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6. | How could read, write, and execute permissions be set on a file called /etc/passwd for all users?
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7. | How could read, write, and execute permissions be removed from a file called /etc/passwd for all users who do not belong to the owner’s group?
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8. | Which command displays the username, connecting line, date of login, idle time, process ID, and a comment for all logged-in users?
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Answers
1. | D. All files need to be owned by someone. |
2. | B. All UIDs and GIDs must be positive and the UID precedes the GID. |
3. | A. The UID of the superuser is always 0, even if the name is changed from root to something else. |
4. | C. Credentials are required, unless blanket access is granted by use of hosts.equiv or .rhosts. |
5. | D. The umask is the default permissions mask. |
6. | A. All users are denoted by “a” in permissions strings. |
7. | D. Permissions are removed with “-”. |
8. | A. The who command displays the username, connecting line, date of login, idle time, process ID, and a comment for all logged-in users. |
