11 Lab Exercises Name ________________________ Date _____________
1. How does single-user mode differ from multiuser mode? 2. How would you communicate each of the following messages? a. The system is coming down tomorrow at 6:00 in the evening for periodic maintenance. b. The system is coming down in 5 minutes. c. Jenny's jobs are slowing the system down drastically, and she should postpone them. d. Alex's wife just had a baby girl. 3. What do the letters of the su command stand for? (Hint: It is not Superuser.) What can you do with su besides give yourself Superuser privileges? How would you log in as Alex if you did not know his password but knew the root password? How would you establish the same environment that Alex has when he first logs on? 4. How would you allow a user to execute privileged commands without giving the user the Superuser password? 5. Assume you are working as Superuser. How do you kill process 1648? How do you kill all processes running kmail? How 6. can you disable SELinux? Put the following line in /etc/sysconfig/selinux: SELINUX=disabled 7. Develop a strategy for coming up with a password that an intruder would not be likely to guess but that you will be able to remember. 8. Give the command $ /sbin/fuser -uv / What is this a list of? Why is it so long? Give the same command as root (or ask the system administrator to do so and mail you the results). How does this list differ from the first? Why is it different? 9. When it puts files in a lost+found directory, fsck has lost the directory information for the files and thus has lost the names of the files. Each file is given a new name, which is the same as the inode number for the file: $ ls -lg lost+found -rw-r--r-- 1 alex pubs 110 Jun 10 10:55 51262 What can you do to identify these files and restore them? 10. Take a look at /usr/bin/lesspipe.sh, and explain what it does and six ways it works. 11. Why are setuid shell scripts inherently unsafe?