3. What happens if we have 2 unique files file1 file2 and we type mv file1 file2, what happens to:

Transcription

1 Prelab 1 Introduction to Linux 1. Review the Linux man pages for chmod, cp, hosts, kill, ls, man, more, mkdir, mv, ping, pwd, rm, rmdir, and tcpdump at Question Sheet for Prelab 1 1. What will happen if you type man man on a machine with a Linux/Unix/Darwin kernel? 2. How can you use the command ls to find out about the size of the file /etc/lilo.con? 3. What happens if we have 2 unique files file1 file2 and we type mv file1 file2, what happens to: a. file1 b. file2 c. mv is calling what commands in this example? 4. What is the command that you issue if you are in directory / and want to copy the file /mydata to directory /labdata? 5. What is the command that you issue if you are in directory / and want to copy all files and directories under /mydirectory to directory /newdirectory? 6. What happens when you type rm * in a directory? 7. What is the command used to delete all files and directories under the directory /mydirectory? 8. Give the command for compressing a directory mydirectory for both tar and zip formats.

2 LAB ONE: Introduction to Linux and Equipment 2 LAB 1: Introduction to Linux In this lab you will familiarize yourself with the lab equipment, i.e., Linux PCs and Cisco switches, as well as some network management tools. NOTE: Remember to reboot the machines before using them by either using the GNOME reboot option or typing reboot in the terminal as root. If you fail to reboot, system settings will linger from the previous users session. NOTE: Please submit file is the standard format: Lab[#]-Ex[#]-[part][#]-PC[#]-command Example: Lab1-Ex2-A1-PC1-ls You should save all files to the Desktop, then either use the GUI to move files or terminal to your USB device once mounted. Network Setup FOR LAB 1 Connect the PCs according to the diagram below to a single switch. Note: do not use port 24 on the switches as it has been configured to behave differently from the other ports you will find out about this in later labs. 1.1 Topology for Lab 1 The table below contains the IP address for each of the Linux PCs; these should be preconfigured: PC IP address of eth0 PC /24 PC /24 PC /24 PC /24-2 -

3 LAB ONE: Introduction to Linux and Equipment 3 Exercise 1 PART A: Setting up The Network Refer to the diagram above to see what the network looks like: A.1: Connect each PC s eth0 port to an associated port on the switch (any port will do for this exercise). A.2: Make sure eth0 is up on each PC by typing in the terminal: ifconfig eth0 This will bring up configuration information about eth0 only. Verify that the ipv4 address is the same as the one shown in the table above. PART B: Testing Connectivity After being connected, all four hosts (Linux PCs) should be able to communicate with each other: B.1: We will use ping to test connectivity between the PCs. B.2. On PC1 issue pings to PC2, PC3, and PC4 by typing: PC1% ping c (Ping to PC2) PC1% ping c (Ping to PC3) PC1% ping c (Ping to PC4) If the ping command fails, make sure to verify that the networking cables are inserted correctly, and ifconfig displays the correct information. Use the KVM switch to switch between PC s (The KVM has 4 LED s and Buttons, each for representing a PC). Save Data: B.3: On PC3 issue pings as you did before to PC1, PC2, and PC4. Exercise 2: Learning Linux Before starting this lab, you should be familiar with the following commands: man pwd ls more tcpdump less mv cp rm mkdir rmdir cat chmod (p)kill ping cd PART A: Familiarizing with Commands The goal of this section is to acquaint yourself with the Linux command line by executing common tasks. Some of the tasks may require multiple commands to complete: A.1: Change to the home directory of root. A.2: Make a directory called test in the directory you just entered. A.3: Copy the file /etc/hosts to the test directory just created. A.4: Change the current directory to test. A.5: Change the name of the file hosts to oldhosts. A.6: Change the permissions on the file such that other users can read but not write to it. A.7: Issue the command ls la and save the output to a file. (part B shows how to use redirection otherwise copy and paste) A.8: Remove all files in directory test. A.9: Remove the directory test

4 LAB ONE: Introduction to Linux and Equipment 4 PART B: Saving Data In the Terminal This section will show you how to save output into a text file for review at a later date: B.1: There are several operators that help modify files. The most common are >>, >, and (pipe). We will be using pipe since it is the most convenient way to redirect one command soutput to another command s input. You can use pipe to send data to another program on the command line, for example to save a text file from a list command: PC% ls tee filename This lists a directory and uses the tee program that opens the file write operator taking input from the standard output of ls and outputting it to the filename from the standard out of each program. Use this to save any data from commands on the command line that you need. B.2: Data can also be saved from the terminal through by cutting and pasting. Highlight information and hit Shift- Ctrl-C, then paste into a text editor with Ctrl-V. Gedit is the GNOME Text Editor and can be run from the GUI main menu or by typing gedit in a terminal window. You can use the & after the command to run it in the background (this means that you can continue to use the same terminal while gedit is running.) B.3: Save the output of the command ls l /usr. PART C: Saving/Copying Files to USB Drive This section will show you how to mount a USB drive in Linux and how to save your files to it. NOTE: Only read the section for the storage method you choose. USB Drive: The process to mount a USB drive is similar to a floppy but requires a little more work at the beginning. After setup it is just a matter of mounting the drive. C.5: First you need to make a directory to mount the USB drive to (assuming it doesn t already exist): PC1% mkdir ~/Desktop/USB PC1% chmod 700 ~/Desktop/USB C.6: Mounting: Now we can mount the drive: PC1% mount /media/nameofusb ~/Desktop/USB That s it! The USB drive should be accessible with all file manipulation commands. NOTE: With most USB drives, Linux will auto-mount, and an icon will appear on the desktop allowing access to the USB drive. Exercise 3: Locating configuration files in Linux In this section a few configuration files will be used to explore the ability to change environment variables in Linux. PART A: Using the more Command - 4 -

5 LAB ONE: Introduction to Linux and Equipment 5 A.1: On PC1 use the more command to look at the following files (DO NOT change these files). Save these files for your lab report. You can either use the cp command or pipe cat to a file. /etc/hosts /etc/sysconfig/network /etc/sysconfig/network-scripts/ifcfg-lo /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth1 BEFORE MOVING ON: Make sure that you have the data you need to be able to answer the following question: 3.1 Which file is used to set the hostname for the Linux PC? What variable is used to set the hostname? 3.2 What is the purpose of the /etc/hosts file? 3.3 Which file is used to configure the IP address of interface eth0? What variable is used to set the IP address? Exercise 4: The Ping command The ping command lets you debug IP networks by sending an ICMP echo request datagram to a remote interface and waiting for an ICMP echo Reply in return. In this way the ping command will discover the distance to the host (measured in time) and other essential information (for example, whether or not the host can be reached). PART A: Issuing a Ping command Save the output of the commands used for your lab report. A.1: On PC1 send five ping messages to PC2 using: PC1% ping c A.2: On PC2, issue a ping with 5 packets (as before) to PC1 A.3: On PC2 issue a ping as before, to the loopback interface, BEFORE MOVING ON: Make sure that you have the data you need to be able to answer the following question: 4.1 Include the output of the ping commands 4.2 Explain the difference between Ethernet interfaces and the loopback interface. I.e. what is the difference between pinging and What are possible uses of the loopback interface? Exercise 5: Using tcpdump Tcpdump allows you to capture traffic on a network and display the packet headers of the captured traffic. It can be used to identify network problems or to monitor network activities. PART A: Simple tcpdump exercise Use tcpdump to observe the network traffic that is generated by issuing ping commands. A.1: On PC1 start tcpdump (saving the output for your lab report) so that it monitors all packets that contain the IP address of PC2 by typing PC1% tcpdump n host A.2: Open a new terminal window and execute a ping command to PC2-5 -

6 LAB ONE: Introduction to Linux and Equipment 6 PC1% ping c NOTE: If you use the tee or tail commands to simultaneously view and save the output from tcpdump, you need to use the l option of tcpdump. The n removes name resolution while l buffers output, this allows for redirecting tcpdump seamlessly. For example, tcpdump n l > filename & tail f filename tcpdump n l tee filename It may be necessary to press Ctrl-C to terminate the tcpdump session. It may sometimes be best to simply redirect the output of tcpdump straight to a file (e.g. tcpdump > filename) and view it afterward with the more command or a text editor. PART B: Another tcpdump traffic capture B.1: On PC1, issue a ping to the nonexistent IP address Save the output for your lab report (you will need to capture stderr). PC1% ping c On PC3, start with the n option: tcpdump n. B.2: Issue a ping (saving the output for your lab report) to the broadcast address using the command: PC3% ping c 1 b BEFORE MOVING ON: Make sure that you have the data you need to be able to answer the following question: 5.1 Include the saved files from Part A and B of Exercise Interpret the results captured in the saved files. 5.3 How many of the Linux PCs responded to the broadcast ping? Exercise 6: Using Wireshark Wireshark is a program that allows you to examine captured packets across a network and analyze them interactively. Wireshark is available for free download at There is documentation available on that site, and a tutorial and tips for how to effectively use Wireshark (formerly Ethereal) can also be found at PART A: Running Wireshark A.1: On PC1: Open a terminal window type wireshark &. This will open the wireshark GUI window and allow you to use the terminal window for other purposes. A.2: Selecting Capture Options: In Wireshark: Step 1: Go to Capture: Options (close pop-up first) Step 2: A display will pop up with Wireshark Capture Options as the title Step 3: Select eth0 in Interface Step 4: Select Capture packets in promiscuous mode Step 5: Select Update list of packets in real time Step 6: Select Automatic scrolling in live capture Step 7: Select Hide Capture info dialog Step 8: Unselect Enable MAC name resolution - 6 -

7 LAB ONE: Introduction to Linux and Equipment 7 Step 9: Unselect Enable network name resolution Step 10: Unselect Enable transport name resolution Step 11: Click Start (wireshark is now running and capturing packets) NOTE: Use these settings for every lab and every time you use Wireshark aside from the interface and filter. KEEP WIRESHARK OPEN, DO NOT CLOSE. PART B: Capture Packets with Wireshark B.1: Wireshark is now running and data needs to be collected (You may have seen some packets from the loopback interface and Cisco protocols being sent across the network). On PC1: PC1% ping c B.2: We can view detailed information about a packet, so choose one that is of type ICMP and click it. You will see all of the packet information (expandable) in the bottom two frames. B.3: Stop the traffic capture by hitting the stop button in the Wireshark Capture window. B.4: Save the data in Wireshark as a text file by: 1- Going to File menu, and selecting the Print option 2- Print selecting the following Format: A)Plain Text option, B)Select Output to File: and input a file name with the FULL path C) Select Packet Summary Line D) Deselect Packet Details. E)Then hit the Print button. The file should now be saved. NOTE: When saving wireshark data in future labs save using Packet Summary Line, unless asked otherwise. BEFORE MOVING ON: Make sure that you have the data you need to be able to answer the following question: 6.1 Include the captured data from the wireshark experiment in the lab report

8 LAB ONE: Introduction to Linux and Equipment 8 REMEMBER TO COPY SAVED FILES TO YOUR USB DRIVE OR FLOPPY! LAB REPORT Exercise 3 Questions: Using the files from the exercise explain and answer the following questions: 3.1 Which file is used to set the hostname for the Linux PC? 3.2 What is the purpose of the /etc/hosts file? 3.3 Which file is used to configure the IP address of interface eth0? What variable is used to set the IP address? Exercise 4 Questions: 4.1 Explain the difference between Ethernet interfaces and the loopback interface. I.e. what is the difference between pinging and What are possible uses of the loopback interface? Exercise 5 Questions: 5.1 Explain what happened when you attempted to ping What packets would you expect to find in a capture, what packets would you expect not to find? 5.2 How many of the Linux PCs responded to the broadcast ping? Include the packet captured lines which support your statement. Make sure to include all saved files with this report