Configuring Your Account (40 points)

Transcription

1 This assignment assumes you have read Chapters 2, 3, 4 and 5 of Sobell. Some specific cross-references may also be given in the questions below. Part I Configuring Your Account (40 points) For this part of the assignment, you will set up a working local CentOS 7 installation on your own computer, and then perform some basic shell configuration tasks. You will duplicate the configuration tasks on your rlogin account. These are intended to make your Linux account more user-friendly and more secure. Your satisfactory completion of the following tasks will be verified by showing your local CentOS 7 installation and your rlogin account to a TA or the course instructor. Task 1: Install VirtualBox 5 and 64-bit CentOS 7 on your own computer. Alternatively, you may run a bootable installation of CentOS 7 on your computer. Note: earlier distributions of CentOS and 32-bit versions are not acceptable. There are copious notes on the course website showing how to install VirtualBox and then install CentOS on it. Most of the errors students encounter doing this can be solved by correctly following the instructions in those notes. Task 2: Modify the.bash_profile, and otherwise use Linux commands, so that the following hold for your local CentOS account: Task 3: 1. Set the bash shell prompt so that it includes the current command number, your user name, the host name, and the current working directory, like so: 1020 wmcquain@centosvm in stuff > 2. Add the current working directory (./) to be the last directory in your path. 3. Set the default file permissions so that newly-created files will allow NO access privileges for users in either group or other. (This is really important for your rlogin account. Hint: see umask.) 4. Define some aliases so that: a. the command shortcut h can be used in place of the command "history" b. the command shortcut hg can be used in place of the command pipeline "history grep" c. the command shortcut lf can be used in place of the command "ls lf" 5. Create a subdirectory ~/2505, with a subdirectory ~/2505/HW01 to use when working on Part II of this assignment. 6. Create a subdirectory ~/bin to hold useful utility programs you may create or receive, and a directory ~/temp to hold files you create for some temporary purpose. You may add these to your path or not, as you prefer. Some of the changes required above are related to discussion of aliases in Chapter 8 of Sobell. Make all of the changes from Task 2 in your rlogin account. Most of those changes are just a convenience or a matter of taste, but the default permissions are vital for accounts on a shared machine! The simplest way to apply these changes to your rlogin account is to use scp to transfer the relevant configuration files from your local CentOS to rlogin. When you have completed the tasks above, demonstrate that to a course TA or the course instructor during office hours. There will be no partial credit for this. You must complete every requirement to receive any credit for Part I. Note: it would be a violation of the Honor Code to show us a local CentOS installation running on another student's machine. You may work in pairs on this assignment! 1

2 Part II Basic Linux Operation (60 points) Prepare your answers to the questions from Part II in a single plain ASCII text file. If you work with a partner, make sure the submitted file contains a properly-completed copy of the partners form posted on the assignments page. Failure to do that will result in at least one of you not receiving credit for the assignment. Submit your file to the Curator system by the posted deadline for this assignment. No late submissions will be accepted. You will submit your answers to the Curator System ( under the heading HW01. For each of the following questions, suppose that your userid is johokie and that a listing (ls -l) of the contents of your current working directory provides the following information: [joehokie@centosvm working]$ pwd /home/joehokie/working [joehokie@centosvm working]$ ls -l total 56 -rwxrwxr-x. 1 joehokie comporg May 10 14:00 driver -rw joehokie comporg 3757 May 10 14:00 driver.c -rw-r--r--. 1 joehokie comporg 531 May 10 14:00 Generate.h -rw-r--r--. 1 joehokie comporg 195 May 10 14:00 Grading.h -rw-rw-rw-. 1 joehokie comporg 528 May 10 14:00 in.txt -rw-r--rw-. 1 joehokie comporg 489 May 10 14:00 MIParser.c -rw-r--r--. 1 joehokie comporg 494 May 10 14:00 MIParser.h -rw-rw-r--. 1 joehokie comporg 2530 May 10 14:00 ParseResult.c -rw-rw-r--. 1 joehokie comporg 2576 May 10 14:00 ParseResult.h Suppose that the permissions of the current working directory, and all directories above it up to and including the user's home directory are set to: drwxrwxr-x. You (johokie) are a member of the group comporg. 1. [14 points] A different user, jillhokie, also belongs to the group comporg, and attempts to perform each of the following operations. Determine whether each operation can be performed by this user; if not, explain exactly which permission setting(s) would have to change in order for the operation to be possible for this user. a) use head to view the contents of the file driver.c b) use head to view the contents of the file in.txt c) use cat to append data to the contents of the file driver.c d) use cat to edit the contents of the file in.txt e) execute the program driver f) copy the file in.txt into her home directory (for which she has full access permissions) g) copy the file MIParser.c into her home directory (for which she has full access permissions) 2. [14 points] Another user, hhoo, who does not belong to the group comporg, attempts to perform the operations listed above. Determine whether each operation can be performed by this user; if not, explain exactly which permission setting(s) would have to change in order for the operation to be possible for this user. a) use head to view the contents of the file driver.c b) use head to view the contents of the file in.txt c) use cat to append data to the contents of the file driver.c d) use cat to edit the contents of the file in.txt e) execute the program driver f) copy the file in.txt into his home directory (for which he has full access permissions) g) copy the file MIParser.c into his home directory (for which he has full access permissions) You may work in pairs on this assignment! 2

3 3. [12 points] Suppose your current working directory is the one shown above, and that you are the user johokie. Give a precise, complete description of the result of executing each of the following commands, in the order given. a) tar cf../working.tar *.c in.txt b) tar cf../working.tar *.h c) tar cf MIParser.c ParseResult.c../working.tar 4. [8 points] Suppose your current working directory on your local CentOS installation is the one shown above. a) Write an scp command that you could use to copy the file MIParser.c to the directory ~/parser on your rlogin user account. b) Suppose your rlogin account contains the file ~/milestone/build.sh. Write an scp command that you could use to copy that file into the ~/temp directory on your local CentOS installation. 5. [12 points] Answer the following questions about various Linux commands. Assume that the user's current working directory contains the following file, named Tolstoy.txt (and the user has rw permissions for the file): The most difficult subjects can be explained to the most slow-witted man if he has not formed any idea of them already; but the simplest thing cannot be made clear to the most intelligent man if he is firmly persuaded that he knows already, without a shadow of doubt, what is laid before him. You are advised to download the file described above and experiment with it. a) Explain why the following command, executed in the directory given earlier, will produce the output that's shown; you do not need to explain why those specific numbers occur. [johokie@centosvm Linux01]$ cat Tolstoy.txt wc b) Explain why the following command, executed in the directory given earlier, will produce the output that's shown; you do need to explain why those specific numbers occur. [johokie@centosvm Linux01]$ cat Tolstoy.txt wc wc c) Describe (do not actually show) the contents of the file Tolstoy.txt after the following command is executed: [johokie@centosvm Linux01]$ head -2 Tolstoy.txt >> Tolstoy.txt d) Describe (do not actually show) the contents of the file Tolstoy.txt after the following command is executed: [johokie@centosvm Linux01]$ head -2 Tolstoy.txt > Tolstoy.txt You may work in pairs on this assignment! 3

4 Some Administrative Commands If you want to be able to test your answers to the first two questions in Part II, you might want to create a second user account on your local CentOS installation. That would let you do some "role playing" when working on assignments like this. The following descriptions are based on my installation of CentOS 7. You'll need root permissions in order to do this, so be sure you know the root password you set when you carried out Part I. In my case, I added a second user account for Joe Bob Hokie (userid johokie), and created a new user group, academic, to which johokie and I belong. Go to the Applications/Sundry menu, and select Users and Groups.* Enter your root password in the dialog box that pops up. You will then see the User Manager dialog Select Add User, and fill in the top four fields in the Add New User dialog. Select OK. You can leave the other settings to their defaults. To add a new user group, select Add Group and specify a name for the group in the dialog that pops up. * First of all, I'm running the Gnome desktop (selectable at the login prompt); if you're running a different desktop environment, things may be organized differently. You may not have this option installed. If so, become root and run yum to install the user management tools: 1189 wmcquain@centosvm in ~> su Password: [root@centosvm wmcquain]# yum install system-config-users Loaded plugins: fastestmirror, langpacks Resolving Dependencies Dependencies Resolved Package Arch Version Repository Size Installing: system-config-users noarch el7 base 337 k Installing for dependencies: rarian x86_ el7 base 98 k rarian-compat x86_ el7 base 66 k system-config-users-docs noarch el7 base 308 k Transaction Summary You may work in pairs on this assignment! 4

5 Install 1 Package (+3 Dependent packages) Total download size: 809 k Installed size: 3.9 M Is this ok [y/d/n]: y Downloading packages: Running transaction Installed: system-config-users.noarch 0: el7 Dependency Installed: rarian.x86_64 0: el7 system-config-users-docs.noarch 0: el7 rarian-compat.x86_64 0: el7 Complete! To set group membership, switch to the Groups tab in the User Manage dialog, select the new group, and choose Properties Scroll and select the users you want to add to the new group. Users can belong to many groups, so this will not remove any existing group settings. Now go back to the Users tab, select a user, go to Properties and select the Groups tab Set the user's Primary Group so that you and the new user share that setting. BTW, a good resource for this is available at: You may work in pairs on this assignment! 5