Your desktop or laptop computer consists of several hardware components:

Transcription

1 Appendix A VirtualBox This appendix describes the role of an operating system on your desktop or laptop computer, how virtualization packages enable you to simultaneously run multiple operating systems on a single desktop or laptop, and how to install and use the open source virtualization package VirtualBox available from Oracle. A.1 Operating Systems A.1.1 What is an operating system? Your desktop or laptop computer consists of several hardware components: a processor chip, which itself may consist of many cores; each core implements the instructions of a particular computer architecture; most desktops and laptops implement the x86 and AMD64/Intel64 architecture; other possible architectures are PowerPC (IBM s processor architecture) and ARM (Acorn Risc Machine, the most common architecture used in tablets and smart phones). random access memory, in which data manipulated by the processor core[s] is stored; this memory is volatile (i.e., is not persistent); persistent disk storage to hold data; this may either be rotational disk storage or solid-state storage; a bit-mapped display to present information to the user; a keyboard to enable textual input from the user; a pointing device (usually a mouse) to enable non-textual input from the user; and a variety of communication devices to enable your computer to interact with other devices (USB, Bluetooth) and with other computers (WiFi, Ethernet). Note that nearly all desktop and laptop computers use processors that implement the x86 and AMD64/Intel64 architecture. 341

2 342 APPENDIX A. VIRTUALBOX An operating system is a program that acts as an intermediary between the user of a computer and the computer hardware. The operating system s goals are: execute user programs to enable users to solve problems; make the computer system convenient to use; and use the computer hardware in an efficient manner. The program that provides this mediation is always running, and is usually called the kernel. Besides providing the kernel, an operating system usually provides a number of standard applications available to a user. A.1.2 Common operating systems There are three common operating systems provided on desktop and laptop computers. Microsoft s Windows; Apple s MacOS; and various flavors of Linux. Each operating system provides a different interface to the user and a different low-level programming interface to the programmer. All three of these operating systems conform to the Posix standards with respect to standard applications and standard programming interface. A.2 Virtualization A.2.1 What is virtualization? In computing, virtualization refers to the act of creating a virtual (rather than actual) version of something, including virtual computer hardware platforms, storage devices, and computer network resources. 1 Hardware virtualization or platform virtualization refers to the creation of a virtual machine that acts like a real computer with an operating system. For example, a computer that is running Microsoft Windows may host a virtual machine that looks like a computer with a variant of the Linux operating system; Linux-based programs can be run on the virtual machine. Since different operating systems provide different standard applications, different user interfaces, and different low-level programming interfaces, virtual machines enable the 1 Much of this discussion has been taken from

3 A.3. INSTALLING VIRTUALBOX ON YOUR DESKTOP/LAPTOP 343 user to use the features provided by one operating system on a machine that is controlled by another operating system, as for the Windows/Linux example above. In hardware virtualization, the host machine is the actual computer on which the virtualization takes place, and the guest machine is the virtual machine. The software that creates a virtual machine on the host is called a hypervisor or virtual machine manager. Virtual machine managers are commercially available (e.g., VMWare); besides the cost of the hypervisor software, there is usually a charge per guest instance that is running on your computer. If you run a proprietary operating system in a virtual machine, you will need to satisfy the licensing requirements of the guest OS in addition to satisfying the licensing requirements of the host OS. A.2.2 Open-source virtualization In an academic scientific environment, the most common operating system used for scientific activities is Linux, which is an open-source operating system. Thus, if you intend to run Linux as a guest OS, there are no licensing requirements to be met to do so. Oracle Corporation has made available an open-source virtualization package called VirtualBox 2. VirtualBox is a powerful x86 and AMD64/Intel64 virtualization product for enterprise as well as home use. Not only is VirtualBox an extremely feature-rich, high-performance product, it is also the only professional virtualization package that is freely available as open-source software under the terms of the GNU General Public License (GPL) version 2. VirtualBox runs on Windows, Linux, and MacOS, supporting a large number of guest operating systems; in particular, it supports a large number of Linux variants. A.3 Installing VirtualBox on your desktop/laptop To install VirtualBox on your desktop/laptop, open your browser and navigate to You should see something like the following in your browser. 2

4 344 APPENDIX A. VIRTUALBOX For the purposes of this appendix, we will assume that you are installing VirtualBox on a Windows host. If you click on Windows hosts in this window, it will bring up a window similar to the following. You should adjust the destination folder for the download file and then click on Save. If you now double click on the file you just downloaded, you will see a window similar to the following.

5 A.3. INSTALLING VIRTUALBOX ON YOUR DESKTOP/LAPTOP 345 By clicking on Next>, the following window will appear. Unless you are extremely adventurous (and know what you are doing), you should accept the default location and feature choices, and simply click on Next>. The following window will then appear.

6 346 APPENDIX A. VIRTUALBOX Again, you are urged to accept the default choices and click on Next>. The following window will then appear. Do not be concerned with this warning, this will not cause any problems with your system unless you have some network file transfer or other current network activity. If so, then you should wait until that activity has completed. Then click on Yes. The following window will then appear.

7 A.3. INSTALLING VIRTUALBOX ON YOUR DESKTOP/LAPTOP 347 You should now click on Install. The system will now install VirtualBox onto your system, providing real-time status as the installation proceeds. After completing the installation, the following window will appear. You should simply click on Finish. The VirtualBox control window will now appear on your screen. We will discuss this window and how to use it to create your Arch Linux virtual machine in Appendix B.

8 348 APPENDIX A. VIRTUALBOX

9 Appendix B Arch Linux This appendix describes how to create a virtual machine using VirtualBox that is executing an Arch Linux operating system image. B.1 Downloading the Arch Linux image The Arch Linux image used in the textbook can be obtained from using your browser, as shown below. When you hit return after inputting this URL into the bar of your browser, a window of the following form should come up in your browser. 349

10 350 APPENDIX B. ARCH LINUX By clicking on the Download button, and then clicking on the Direct download option, the following window should appear on your screen. Place CISCommon.vdi somewhere on your file system, and remember where you put it. B.2 Creating your virtual machine in VirtualBox When you clicked on the Finish button at the end of Appendix A, you will have seen the VirtualBox control window, similar to the following.

11 B.2. CREATING YOUR VIRTUAL MACHINE IN VIRTUALBOX 351 Click on the blue circle with the label New underneath to create a new virtual machine. You will then be asked to provide some configuration information to assist VirtualBox. The first window you will see looks like the following. You must fill in the three fields; the next figure shows these fields filled in.

12 352 APPENDIX B. ARCH LINUX You may name the virtual machine anything you like; the second and third fields must be exactly as seen in the above figure. When you click on the Next button, the following window will be shown. Click on the Next button, accepting the recommended memory size of 1024 MB. The following window will then be shown.

13 B.3. STARTING, STOPPING, AND USING YOUR VIRTUAL MACHINE 353 This window comes up with the Create a virtual hard disk now radio button selected. You should click on the Use an existing virtual hard disk file radio button, and click on the folder icon to select the CISCommon.vdi file that you downloaded in Section B.1. Then click on the Create button. VirtualBox will then display things to you as it creates the virtual machine. Ultimately, you will be presented with the following screen in the VirtualBox control window. B.3 Starting, Stopping, and Using Your Virtual Machine B.3.1 Starting your virtual machine You can see from the control window above that it has created a virtual machine named CaDS, and that it is in the Powered Off state. Double click on CaDS (or whatever you named your virtual machine) to start it running. You will be shown a number of things as your virtual machine is booting. Eventually, you will see the following window, which is inviting you to log in under the account me, password me.

14 354 APPENDIX B. ARCH LINUX After typing me in the box, followed by hitting the Enter key, you will see the following desktop displayed. B.3.2 Starting a terminal window The icon in the lower left corner of the desktop, (which looks like this ) is the application launcher. If you click on that icon, you will see the following window.

15 B.3. STARTING, STOPPING, AND USING YOUR VIRTUAL MACHINE 355 If you now place your mouse directly over the Applications icon at the bottom of this window, you will see the following window. If you now click on the System menu item, you will see the following window.

16 356 APPENDIX B. ARCH LINUX The last line of this menu is for xterm, which will create a terminal window in which bash is reading your commands. Click on that line, and you should see the following window. Try typing echo this in the terminal window to see if bash is working correctly in the terminal window. You can create as many terminal windows on the Linux desktop as you wish. Clicking in the title bar of a window on the desktop and dragging with the mouse enables you to move the windows around on the desktop. You can close the terminal

17 B.3. STARTING, STOPPING, AND USING YOUR VIRTUAL MACHINE 357 window by typing ctrl-d, by typing a command exit, or by clicking on the black x in a white circle in the top right-hand corner of the xterm window. B.3.3 Starting the web browser You may have noticed the icon for a web browser when you clicked on the application launcher. The web browser icon is a blue circle with a dot in the middle; clicking on this icon will bring up the Chromium web browser on your Linux desktop, as in the following window. 1 1 Note that the first time that you bring up the web browser, it may take some time before the browser window appears; it may also ask you for a password for a KDE wallet - the password is "CISCommon", without the quote marks.

18 358 APPENDIX B. ARCH LINUX You should try to explore the web in the browser. Note that the open windows on the Linux desktop have labels that are shown at the bottom of the desktop. Clicking on the label for a window that is hidden will cause it to rise to the top. Clicking on the label of a window that is on top will cause it to be hidden. B.3.4 Stopping your virtual machine To stop your virtual machine (similar to closing your laptop, causing the real operating system and applications to sleep), click on the File menu tab at the top of the window, and click on the Close... menu item. You will then see the following window. Before clicking on the OK button, you must make sure that the Save the machine state radio button is selected! When you click on the OK button, VirtualBox will tell you that it is saving the state, and the VirtualBox control window will look as follows.

19 B.4. ESTABLISHING A SHARED FOLDER ON YOUR HOST 359 It now shows that the virtual machine CaDS has been saved. When you double click on it in the future, it will pick up right where you left off. B.4 Establishing a shared folder on your host VirtualBox, like many other virtualization platforms, enables you to mount a folder on your host machine as a file system in your Arch Linux guest. This sections shows you how to do so. Start up your virtual machine as described in Section B.3. Start up a terminal window as described in Section B.3.2. Click on the Devices Menu at the top of the virtual machine window, and click on the Shared Folders menu item, and then click on the Shared Folders Settings... sub-menu item. You should see something like this.

20 360 APPENDIX B. ARCH LINUX In your host system, you need to create a folder/directory that can be mounted within your Arch Linux virtual machine. I created an empty folder on my Windows machine named C:\share. You can name your folder whatever you want, just remember its full pathname as you will need it in the next step. In the previous window, click on the blue folder icon in the right margin that has a green plus sign in it. This will result in the following window being shown.

21 B.4. ESTABLISHING A SHARED FOLDER ON YOUR HOST 361 If you click on the drop down icon on the Folder Path: line, it will show you a folder with a green caret character, labelled Other... ; by clicking on this, you can navigate to the folder that you created on the host system, in my case C:\share, and select it. After you select the folder, it will put the full pathname in the Folder Path: line, will place a name in Folder Name:, and will check the Read-only box. In my case, it named the folder share ; I could change it, but this is fine. You will need the name of the folder in a later step. You should uncheck Read-only and check both the Auto-mount and Make Permanent boxes. The final state of this dialog box before clicking on OK is shown below. If you now click on OK, the following should appear on your screen.

22 362 APPENDIX B. ARCH LINUX Click on OK to return to the virtual machine desktop. The previous activities have told the host to serve up your folder as a shared disk. You now need to mount that folder in your Arch Linux system. In your xterm window, you need to type the following command: sudo mount -t vboxsf share /home/me/share The sudo command enables you to execute one command as the root user; you may be prompted for the password for your account (me, password me). This mounts the shared folder as the directory /home/me/share; you can also refer to this shared folder as ~/share. If you stop your virtual machine as described in Section B.3.4, this shared folder remains mounted every time you start up the virtual machine. If, on the other hand, you stop your virtual machine by selecting the Send the shutdown signal radio button, the mount will be lost. When you restart your virtual machine the next time, you will need to execute the sudo command above. Alternatively, you can add an entry to /etc/fstab so that the shared folder is mounted everytime the system is rebooted (i.e. started after stopping using the shutdown signal). Using your editor, append the following line to /etc/fstab 2 : <name_of_share> /home/me/share vboxsf defaults Assuming your editor is named editor, your command line will need to be sudo editor /etc/fstab

23 B.4. ESTABLISHING A SHARED FOLDER ON YOUR HOST 363 where <name_of_share> is replaced by the name of the share, in our case it is share. After you add this line to /etc/fstab, you will need to stop your virtual machine using the Send the shutdown signal option, and then restart your virtual machine. Regardless of whether you automate the mounting through an entry in /etc/fstab or you choose to mount by hand whenever you reboot, you should try creating a file in ~/share, perhaps by executing the following command in the terminal window. echo this is a test >~/share/tmp.txt Then, on your host system, you should access tmp.txt in the shared folder; in our case, it will be C:\share\tmp.txt. You should also create a text file in the shared folder on the host, and then access that file from the xterm window on your virtual machine.

24 364 APPENDIX B. ARCH LINUX

25 Appendix C Bitbucket Most software developers have discovered that it is essential to maintain an archive of your software artefacts to protect yourself from disk or computer failures. In order to provide this protection, the archive must be on a different computer system. It is a good idea for you to develop good habits in this regard at an early stage in your computer science career. This appendix describes a hosting site upon which you can create respositories that can be accessed using the git family of tools (described in Appendix D). Any other git repository hosting site will work as well, but this one enables academic creation of private repositories at no cost. Most other git repository hosting sites charge to be able to create private repositories. 1 Atlassian, Inc. provides this git repository hosting site at The remainder of this appendix assumes that you do not currently have an account at bitbucket.org. Obviously, if you already do, you do not have to create an account. Using your browser, go to You should see a window like the following. 1 If you use a repository for keeping your software, it must be private to prevent any of your classmates from looking at your solutions without your knowledge, and potentially plagiarizing your work. 365

26 366 APPENDIX C. BITBUCKET Click on the blue box labelled Get started for free to yield the following window. You should enter your UO and click on Continue. In the following screen, I have entered jsventek@cs.uoregon.edu, my full name, my password, and clicked on the box stating that I am not a robot.

27 367 Clicking on the Continue link, yields the following window. You need to access your inbox. You should see a message like the following. Click on the Verify address button, and you will now see a window like the following in your browser (usually in a new tab), although the box will be empty where I have entered jsventekcs.

28 368 APPENDIX C. BITBUCKET Choose a unique username on Bitbucket, enter it in the box, and click on the Continue button to yield the following. Note that I have indicated the values you should select from the drop-down fields on this figure. You then click on the Submit button to yield the following.

29 You can logout from Bitbucket by clicking on the person icon in the lower left corner of this window, and then clicking on the Log out menu item. 369

30 370 APPENDIX C. BITBUCKET

31 Appendix D git Appendix C described how to create an account on a remote repository hosting site in which to maintain source files and other artefacts in a controlled fashion. This appendix describes basic uses of git with that hosting site. D.1 Creating a new repository You should create a new Bitbucket repository to hold projects from this course. In the following, I will assume that the repository is named uoregon-cis212. Of course, you can call it anything you like. Initially, the repository you create in Bitbucket is empty, without any code in it. The Bitbucket repository is the central repository for your files. After creating a repository, you ll make a copy of the repository on your virtual machine - that way you can update/add files in your local repository, then tranfer those changes to the central repository. Log into your Bitbucket account from your browser, at which point you should see the following window. 371

32 372 APPENDIX D. GIT Click on the Create Repository button, which yields the following window. In this figure, I have entered uoregon-cis212 in the repository name box; you need to enter a name for the repository in this box. The rest of the options in the figure have the following meanings: Access level - Leave the This is a private repository box checked. As discussed earlier, a private repository is only visible to you; if this box is unchecked, anyone can see your files in this repository. Include a README? - If you recently created your account, this defaults to a tutorial README. Version control system - Since we are using git, keep the Git radio button set. Now click the Create repository button to yield the following window.

33 D.2. CLONING YOUR REPOSITORY 373 You may now logout from Bitbucket, as all remaining activities with the repository will be performed within your virtual machine. D.2 Cloning your repository You may have noticed in the last window in the section above, you are provided with a command line to type into a terminal window to create a copy (clone) of the repository in your virtual machine: 1 git clone Typing this into a terminal window in your virtual machine will do the following: Requests your password for your account on bitbucket.org - this will not be echoed. Creates a directory named uoregon-cis212 in the current directory. Creates a copy of README.md, which is the only file in the repository, in the uoregon-cis212 directory. It also creates a directory named.git in that directory; this has all of the control information that git needs to enable the synchronization of additions/changes to your local information with the central repository on Bitbucket. While the clone operation is working, it prints summary statistics on standard output. 1 Of course, the occurrences of jsventekcs in the above will be replaced with your unique Bitbucket username, and if you did not name your repository uoregon-cis212, that will be replaced with the name of your repository.

34 374 APPENDIX D. GIT D.3 Using your repository It is recommended that you keep the source files, Makefile, associated shell scripts, and documentation for each project or assignment in a separate directory within the local repository directory, in this case uoregon-cis212. In the following, we use git to manage an assignment named Test. Change your working directory to the local repository directory and create a directory named Test. $ cd /home/me/uoregon-cis212 $ mkdir Test Add a file named readme.1st to that directory. $ echo First line of readme.1st >Test/readme.1st At this point, we have simply created a directory and a file. We need to add the Test directory and all of its contents to the repository. $ git add Test This simply adds those filenames to the repository. They do not become a permanent part of the respository until we commit them. $ git commit -m "Directory for Test" Test The first time you do this, git will complain that it does not have information that it needs to link up with Bitbucket. You will need to execute the following two commands: $ git config --global user. "jsventek@cs.uoregon.edu" $ git config --global user.name "Joe Sventek" where the quoted arguments should be the address you used for your Bitbucket account, and your name should be your name. After you have configured this information, you must re-execute the commit command. Now the Test directory and its contents have been committed to the repository. To update the repository on Bitbucket with this new content, you must push the changes. $ git push You will be asked for the password for your Bitbucket account, and then git will log

35 D.4. HINTS AND ADDITIONAL INFORMATION 375 statistics about the update. After a push, the central respository is identical to the local repository. D.4 Hints and additional information The biggest mistake that students make is to create the repository on Bitbucket, and then forget to commit changes and push the changes back to the central repository. It is strongly recommended that as you make changes to your sources, you should commit and push the changes to the central respository often. Failure to do so will be crippling if your host machine or your virtual machine crash or break, as your most recent activities will not be archived on Bitbucket. git is a very powerful software package. There are a number of tutorials that cover all of its aspects. One that has proven useful for students may be found at

36 376 APPENDIX D. GIT