OPS235 Lab 4 - Fedora17

Working with Partitions / User & Group Management

Introduction

• In this lab, you are going to learn how to create and format partitions. You will be creating partitions by using both graphical and command-line utilities.

• Also in this lab, you will learn how to manage (add, delete, modify) user accounts on your Fedora systems. You will also learn how to create and maintain groups to allow users to share and protect data.

Objectives

1. Identify and define major entries in the /etc/passwd, /etc/shadow, and /etc/group files.
2. Learn about partitions, and how to add "virtual partitions with LVM.
3. Learn how to create a "virtual partition" in a Virtual Machine.
4. Learn how to add and remove and modify user accounts.
5. Learn how to create and manage groups.

Required Materials (Bring to All Labs)

• Fedora 17 LIVE CD
• Fedora 17 x86_64 Installation DVD
• SATA Hard Disk (in removable disk tray)
• USB Memory Stick
• Lab Logbook

Prerequisites

• Completion and Instructor "Sign-off" of Lab 3: OPS235 Lab 3

Linux Command Online Reference

Each Link below displays online manpages for each command (via http://linuxmanpages.com):

LVM Management Utilities:	User / Group Management:
vgs lvs pvs fdisk lvextend lvcreate pvcreate vgextend mount umount	/etc/passwd File /etc/skel File /etc/group File useradd userdel usermod groupadd groupdel chmod

Resources on the web

Additional links to tutorials and HOWTOs:

• Logical Volume Management
• Partitioning with fdisk
• Mounting / Unmounting File-systems
• UID and GID explained

Creating / Formatting / Mounting Partitions

Do not Shut-Down VMs Until Instructed
You will be running all 3 VMs eventually when performing this tutorial, Leave all VMs running until you are instructed to shut them down at the end of this lab.

Investigation 1: How to Add a PV to an existing VG (Graphical Method)

Perform this investigation on the VM named fedora1.

In this investigation we will be adding an additional 2 GB virtual disk to our fedora1 system, and use it as an additional physical volume...

1. Start virt-manager.
2. Shutdown fedora1 if it is running.
3. Open the console window for fedora1.
4. Select the menu option View>Details.
5. Click Add Hardware button at the bottom left-hand corner.
6. Make certain to remain in the default section called "Storage".
7. Make the following selections in this "Storage" dialog box:

Suggested settings in the Storage dialog box to create a virtual Hard Disk.

• Under Create a disk image on the Computer's Hard Drive, change the size to 2 GB.
• Do not click on the Select Managed or Other Existing Storage radio button. Since no file pathname is provided, then the system will assign a name in the directory. You/var/lib/libvirt/images/.
• Select Device Type: Virtio Disk
• Select Storage Format: raw
• Click FINISH to proceed.

8. Boot the system. You should now have both /dev/vda and /dev/vdb.
9. Record the size of the volume group and the amount of free space (Hint: use a command that you learned in a previous lab).
10. Use the system-config-lvm tool to add the new virtual disk to the volume group, then extend the size of the root partition using the newly-added space

Answer the Investigation 1 observations / questions in your lab log book.

Investigation 2: How to Add a PV to an existing VG (Command Line Method)

The investigation relate to fedora3.

1. Check and record the current state of your storage (use df -h, lvs, vgs, pvs).
2. Make reference to the following command line resource for assistance: Logical Volume Management
   • (Hint: First view section on Adding a Physical Volume. Also, write down the commands first and check prior to issuing them in sequence. This is not looking for the commands necessary to add a physical volume to the virtual machine. It is based on the assumption that the virtual machine already has the physical disk added to the machine via virsh or virt-manager.)

1. Perform the same operations on fedora3 that you did in the Investigation 1 on fedora1:
   • Add a virtual disk to the system.
   • Partition the disk (use fdisk - refer to the manpages for details as necessary).
   • Make the new partition a physical volume (pvcreate).
   • Add the PV to the existing volume group (vgextend).
   • Confirm that the VG is now larger (pvs, vgs).
   • Extend the root filesystem using the new space (lvextend).
   • Confirm that you were successful (lvs, df -h).

Answer the Investigation 2 observations / questions in your lab log book.

Investigation 3: Manually Mounting / Unmounting Filesystems

Perform this investigation on the VM named fedora2.

So far, we have simply assumed that when the Fedora OS boots-up, that its file-system is automatically available. In this investigation, you will learn how file-systems (or portions of file-systems) can be mounted or "connected" to existing file-systems. You will also learn how to unmount (or "disconnect") portions of file-systems from existing file-systems.

1. Boot-up your Fedora2 VM.
2. Open a terminal and login as root.
3. Issue the command called mount . This command provides information relating to various partitions (logical volumes) and corresponding "mount points" (directories).
4. Record the information from issuing the mount command for both lv_root and lv_home. What commands would issue to quickly obtain this information?
5. Issue the command umount /archive. Did anything happen? Issue the mount command again. Is there any difference with the command output?
6. View the online man pages for the mount command. Issue the mount command with arguments to "re-connect" the device /dev/mapper/vg_fedora2-lv_archive to the /archive directory (refer to the section Linux Command Online Reference above).

File-System Type Option No Longer Required for Mount Command
When viewing examples online, you may notice that the -t option is used with the mount command to indicate the version or type of file-system to mount.
The -t option is no longer required for the mount command, However, it can be used to restrict the mount command so that it only mounts the filesystem if it of the type listed in the -t option.

7. Explain how the mount command would be useful for Linux system administration.
8. Unmount the /archive directory.
9. Issue a command to verify that he /archive directory has been unmounted.

Answer the Investigation 3 observations / questions in your lab log book.

Investigation 4: How Partitions are Automatically Mounted Upon Boot-up

Perform this investigation on the VM named fedora2.

1. Create a directory called /storage (i.e. storage is a subdirectory of the root directory)
2. Check the man page for /etc/fstab by entering the command man fstab
3. Edit your /etc/fstab file to mount the partition /dev/mapper/vg_fedora2-lv_archive to /storage
4. Issue this command:

mount -a

5. What does that command do?
6. Confirm that the partition mounted.
7. Issue a command to list the contents of /storage. Are there any files?
8. Reboot the fedora2 VM, and verify that /storage has now been automatically mounted.
9. In the previous investigation, we mounted the directory as /archive, but in this investigation we automatically mounted it as /storage. What purpose does could this server for a Linux system administrator?

Answer the Investigation 4 observations / questions in your lab log book.

User/Group Management

Investigation 5: The /etc/passwd file

Perform this investigation on the VM named fedora1.

1. Read about the file: http://linux.die.net/man/5/passwd
2. Now look at the contents of the /etc/passwd file.
3. Make note of the contents of that file, and make certain and record in your lab log-book the information that each field contains.
4. Why do you think there are so many users?
5. Look at the names of the users. What do you think these user names represent? Are they people?
6. What is the numeric user ID (UID) of the root user?
7. The user IDs of real users (people) are different from the user IDs of system accounts. What is the pattern?

Answer the Investigation 5 observations / questions in your lab log book.

Investigation 6: Adding users

Perform this investigation on the VM named fedora1.

1. Read the man page for the useradd command.
2. Create a new user account for each of your pod-mates, using their learn account name as a user name. Give each user a password.
3. Use the grep command to obtain information for each of the newly created users within the /etc/passwd file.
   • What is the home directory of each user?
   • What group is each user in?
   • What else do you know about each user?
   • Where are the passwords stored?
4. Look at the man page for /etc/shadow using the command man 5 shadow
   • Grep the /etc/shadow file for each of the new users.
   • Make note of this information.
   • What is the purpose of the /etc/shadow file?
5. Create two new dummy users, ops235_1 and ops235_2.
6. Investigate the home directory of one of your new users.
   • What files are there? Be sure to include hidden files.
   • What do you think these files are used for ?
   • How does the operating system determine which files are created in a new home account?
     The answer can be found here: http://www.linuxhowtos.org/Tips%20and%20Tricks/using_skel.htm
   • Look at the files (including hidden files) in the template directory referred to in the article. Compare them to what is in a home directory for a new user. What do you notice?
   • Create a new file in this directory with the following command: touch foo
   • Create a new user named foobar, with the option to automatically create a home directory.
   • Look at the contents of foobar's home directory. What do you notice?

7. Boot-up your fedora3 VM.
8. Create a new user using your Matrix account user-name.
9. Issue a command to verify that you have created this user account.

Answer the Investigation 6 observations / questions in your lab log book.

Investigation 7: Managing Groups

Use fedora1
Perform these steps in the fedora1 virtual machine.

1. Read the man page for the groupadd and groupdel commands.
2. Note which option allows you to set the Group ID number (GID) when you create a new group.
3. Examine the file /etc/group
   1. Which values of GID are reserved for system accounts?
   2. Which values of GID are reserved for non-system user accounts?
   3. What is the lowest available GID number for non-system users?
   4. What is the default group name of a new user?
   5. Add a new group named ops235 with a GID of 600.
   6. You are angry at some irresponsible users on your system.
      • Add a new group named idiots.
      • Look at /etc/group and note the GID of idiots.
      • What GID is given to a new group if you do not specify it?
      • Your anger has subsided. Delete the idiots group.
      • Look at /etc/group again and note the change.

Be sure to record your observations in your lab notes.

Answer the Investigation 7 observations / questions in your lab log book.

Investigation 8: Deleting users

Use fedora1
Perform these steps in the fedora1 virtual machine.

1. Read the man page for the userdel command. Note which option automatically removes the users home directory when that user is deleted.

1. Delete the user ops235_1 using the command userdel ops235_1
2. Delete the user ops235_2 using the same command with the option which removes the home directory of the user.
3. Check the contents of the /home directory. What do you notice?
4. Check the contents of the /etc/group directory. What do you notice?

Answer the Investigation 8 observations / questions in your lab log book.

Investigation 9: Modifying users

Perform this investigation on the VM named fedora1.

1. Read the man page for the usermod command. Note which options change the user's full name, primary group, supplementary groups, and shell.
2. Add each of your new pod mate accounts to the group ops235 (in other words, add ops235 to each user as a supplementary group).
3. Examine /etc/group. What has changed?
4. Experiment with your pod-mate accounts to share and deny access to same group members by creating directories and files, and use the chmod command. How is the /etc/group related to file sharing permissions?
5. Use the usermod command to associate each of your pod mates' full name to their user name, as shown in your text. With each change, examine their entries in the /etc/passwd file. What has changed?
6. Just for interest, how would you use a graphical utility to modify user account information?
7. Be sure to record your observations in your lab notes.

Shutdown VMs
It is time to safely shut-down all of your Virtual Machines. Please proceed to Completing the Lab

Answer the Investigation 9 observations / questions in your lab log book.

Completing the lab

Time for a new backup!
If you have successfully completed this lab, make a new backup of your virtual machines. Remember to also make a backup of the new second virtual disk drive on fedora1 -- you now have two virtual disks on fedora1, and therefore two image files, and therefore will need two backup files.

Arrange proof of the following on the screen:

1. Increased volume group size for fedora1 VM.
2. Correct Linux command sequence to Add a PV to an exiting VG
3. /etc/fstab entry in fedora2 VM to automatically mount /storage
4. Proof of ops235 group entry in /etc/group in fedora1 VM
5. Proof of pod-mate user account information in /etc/passwd in fedora1 VM.
6. Proof of VM backups.

Preparing for Quizzes

1. What is the reason to extend a Volume Group?
2. What is the purpose of the file called /etc/fstab?
3. How do you ensure that a file-system is mounted every time that a system is started?
4. What are the purposes of the following files: /etc/passwd, /etc/shadow, /etc/group?
5. Explain the purpose of the /etc/skel directory.
6. What do the terms UID and GID represent. What is their purpose?
7. List the steps to create a user account on a system.
8. List the steps to change user account information on a system.
9. List the steps in order for users to share file and directory accounts as "same group members".
10. List the steps to remove a user account. What is required to remove a user account's home directory as well?