I have an online exam today. it will open after 45 minutes. Now I have attached a sample exam for you. so that you can prepare for it.
Question 1 Using the tables below explain why the maximum partition size is 2TiB and the maximum disk size is 4TiB using an MBR on a disk with a 512byte sector. (Please show any calculations employed and remember a difinitve number is not required. If you need to represent exponentiation use a caret ^ or double-star **. For example, 2^4 = 16, or 2**4=16 The structure of the Master Boot Record Address Description Size (bytes) Hex Dec 000 0 Bootstrap Code 218 0DA 218 Disk Time-stamp 6 0E0 224 Boostrap Code (cont.) 216 1B8 440 Disk Signature 6 1BE 446 Partition 1 16 1CE 462 Partition 2 16 1DE 478 Partition 3 16 1EE 494 Partition 4 16 1FE 510 Boot Signature 16 Total Size 512 The 16 byte Partition entry in the MBR Length (Bytes) Description 1 Status 3 Cylinder-Head-Sector (CHS) address of partition’s first sector 1 Partition Type 3 Cylinder-Head-Sector (CHS) address of partition’s last sector 4 Logical Block Address (LBA) of partition’s first sector 4 Number of sectors in partition 16 Total size of entry Question 2 List the underlying actions taken by a utility program, such as “adduser” or “useradd” when a new user account is created. Q3 Explain why you should never shutdown any computer system by switching off the power! How should it be shutdown? Q4 For over 40 years the critical first process a Unix kernel would start was “init”. In the last 15 years “init” has been systematically replaced by “launchd” (macOS) and “systemd” (all Linux distributions). Explain the purpose of the first process, and why it was thought necessary to replace “init”. Q5 The Unix remote access services rlogin, rsh and rcp have been replaced by the ssh service. • Explain why the Unix services rlogin, rsh and rcp should not be used, • and how the ssh service overcomes their drawbacks. Q6 Consider the following command to rename a file: prompt> mv chapter1.tex /old/chapter1.tex Explain the steps taken by the shell to start the executable file /bin/mv running on a Unix system. Q7 Consider the following nftables script: #!/usr/sbin/nft -f add table ip filter add chain ip filter INPUT { type filter hook input priority 0; policy drop; } add rule ip filter INPUT iifname "lo" accept add rule ip filter INPUT ct state related,established accept Explain how the above rules establish a bare minimum firewall. Q8 There are two different types of encryption: “symmetric” key encryption and “asymmetric” key encryption. • Explain the differences between each method. • Why are there two methods? • Give an example where each method would be used Q9 The default PATH environment variable for a user is normally: /usr/local/bin:user/bin:/bin • How can the PATH string be modified so that users do not have to type ./myApp to run their own applications, but just: myApp? • Why is this modification not in the default PATH string. Q10 Consider the following daily backup schedule using backup levels— Sun Mon Tues Wed Thur Fri Sat 0 6 7 1 3 4 2 Using the above schedule and assuming that all backups start at 8:15PM of the day specified, answer the following questions: • What files will be on Thursday’s backup • Suppose there is a disk failure early Saturday morning and the disk has to be rebuilt completely from the backup tapes. Which tapes need to be used and in what order? Q11 The Web Servers, Nginx and Apache, both allow the configuration of “Virtual Hosts”. What is a “Virtual Host”, and how are virtual hosts distinguished? Q12 Explain why TCP-wrappers or Systemd IP filtering are used as well as netfilter packet filtering Q13 You are looking for the file assignment.txt. You use the following sequence of commands to find it. prompt> locate assignment.txt /home/georges/CSC3412/Ass1/assignment.txt prompt> cd /home/georges/CSC3412/Ass1/ prompt> ls -l assignment1.txt ls: No such file or directory Please explain the apparent contradiction suggested by this sequence of commands Q14 Consider the following systemd service file: 1. [Unit] 2. Description=LXC Container Initialization and Autoboot Code 3. After=network.target lxc-net.service 4. Wants=lxc-net.service 5. 6. [Service] 7. Type=oneshot 8. RemainAfterExit=yes 9. ExecStartPre=/usr/lib/x86_64-linux-gnu/lxc/lxc- apparmor-load 10. ExecStart=/usr/lib/x86_64-linux-gnu/lxc/lxc-containers start 11. ExecStop=/usr/lib/x86_64-linux-gnu/lxc/lxc-containers stop 12. Delegate=yes 13. StandardOutput=syslog 14. StandardError=syslog 15. 16. [Install] 17. WantedBy=multi-user.target In the context of this service file only: • explain lines 3 and 4 • explain lines 9, 10, 11 q15 You vDSL modem connecting your household to the Internet will have the following iptables rule defined (or something very similar): iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE • Why is this rule necessary? • What does this rule do? • What does it tell you about the interface ppp0? • Why is the MASQUERADE key word required for most households. Question 16 Why is it important for the system administrator to know what services are running on a computer? In your answer first explain what a “service'” is. Question 17 Consider the following synopsis line from a UNIX man page SYNOPSIS tar -c [-f archive] ... [file...] tar -t [-f archive] ... [member...] tar -x [-f archive] ... [member...] Explain the purpose of the synopsis lines (not the command itself), including how the lines are to be interpreted. Q18 Netfilters defines three chains (iptables) or three chain hooks (nftables) called INPUT, OUPUT, and FORWARD. How does Netfilters know which of these chains a packet has to traverse? Q19 The services DNS, DHCP, NTP all use UDP packets for communications, while services such as HTTP, SMTP, SSH use TCP packets — Why? Q20 To be able to use an IPv4 network, an interface must be assigned a “network address” and a “netmask”, Explain why the addition of the “netmask” is essential for IPv4 addresses and not required for IPv6 unicast addresses Q21 When a user logs-in to a Linux machine directly via the graphical login window on the computer’s monitor—the Xserver is restarted and configured to only allow connections from Xclients run by the user who just logged in. Explain the security reasons for restricting access to the Xserver in this way Ques22 i)Why are file-systems placed on hard disks, flash drives, and optical disks but not on tapes ii) What file information is stored on tapes, if they do not use file systems? Q23 LVM software claims to be able to increase I/O speeds—how is this done? Q24 Unix/Linux provides a logging system via the dæmon syslogd. Why is it important for an operating system to have a standardised system-wide logging facility? Q25 Consider the following DNS zone file: 1| usq.edu.au IN SOA ns1.usq.edu.au 2| admin.usq.edu.au ( 3| 2016052300 ; Serial Number 4| 10800 ; Refresh 5| 1200 ; Retry 6| 864000 ; Expire 7| 3600 ) ; Minimum 8| 9| NS ns1.usq.edu.au. 10| NS ns2.usq.edu.au. 11| 12| MX 10 m1.usq.edu.au. 13| MX 20 m2.usq.edu.au. 14| 15| ns1 IN A 139.186.53.4. 16| ns2 IN A 139.186.53.5. 17| m1 IN A 139.186.73.4. 18| m2 IN A 139.186.73.4. 19| 20| 4.53.186.139.in-addr.arpa. IN PTR ns1 21| 5.53.186.139.in-addr.arpa. IN PTR ns2 Explain lines 9 through to 21