LABS

During the Red Hat exams, the tasks will be presented electronically. Therefore, this book presents most of the labs electronically as well. For more information, see the Lab Questions section toward the end of Chapter 5.

For Labs 5 and 7, you'll need to execute scripts from the Chapter5/ directory of the CD included with the book. For example, the script for the fifth lab is called Ch5Lab5. In all cases, you'll need to copy the script to the server1.example.com test system. The following steps assume the system is on a KVM-based virtual machine. If it's on a different virtual machine manager such as VMware or Virtualbox, you'll have to consult the documentation for that virtual machine manager, at least for instructions on how to connect a CD/DVD drive. But remember, only KVM is a virtualization technology found on RHEL 6. Don't look at the contents of the copied scripts or files, or the files in the /root/backup directory, until the lab is complete. The following are steps common to those first four labs.

1. Open the KVM Virtual Machine Manager from a GUI command line with the virt-manager command.

2. Connect to the localhost (QEMU) system.

3. Double-click the virtual machine with the server1.example.com system. In the window that appears, click View | Details.

4. Insert the CD for the book. Use the options that appear to connect the CD/DVD drive to the virtual machine. Return to the console for the virtual machine by clicking View | Console.

5. Boot the server1.example.com system. Mount the book CD with the mount /dev/cdrom /media command.

6. Log in to the root administrative account.

7. Make sure you're in the /root directory with the cd /root command. Copy the noted scripts (and associated test files) from the CD to the root user's home directory with the cp /media/Chapter5/Ch5Lab* ~ command.

8. These labs should work even if the /root/backup directory exists, though you'll see an error message if it does.

9. Make sure the scripts are executable; run the chmod +x Ch5Lab? command.

Lab 1

This lab is focused on runlevels and the boot process. You'll boot a system into runlevel 1, with a full display of all boot messages. You'll then set up the system to boot into runlevel 2 by default.

1. On what part of the boot hard drive is the first stage of the GRUB bootloader typically located?

2. Power- up the local system. During the boot process, when you see the following message (the operating system name and version number may vary), press a key.

Booting Red Hat Enterprise Linux Server (2.6.32-71.el6.x86_64) in 5 seconds....

3. Edit the default option. If the GRUB bootloader is already password-protected, press P and enter the password.

4. Press A to edit the kernel command line.

5. What do you need to change and add to that command line to boot the system into runlevel 3 with all boot messages displayed?

6. Make required changes, and proceed with booting into runlevel 3.

7. Once the system is booted, what command verifies the current runlevel?

8. Open the /etc/inittab configuration file. What's the current default runlevel? Make a note of that number.

9. Edit the /etc/inittab configuration file so that the system boots normally into runlevel 2.

10. Reboot the system. How do you confirm that the changes worked?

11. Edit the /etc/inittab configuration file. Restore the original default runlevel.

Lab 2

This lab is focused on one thing you can do when booting into runlevel 1, also known as single-user mode. As suggested by a now-superseded version of the RHCSA objectives, in this lab you'll change the root administrative password. But here's a twist: assume that you don't know the current version of that password. What do you do?

Lab 3

In this lab, you'll add one layer of security to the local system, by adding an encrypted password to the GRUB menu.

Lab 4

In this lab, you'll set up a second stanza in the GRUB configuration file. Before getting started, it's best to back up the file. For example, the following command backs up the file to the root user's home directory (/root):

# cp /boot/grub/grub.conf ~

In the second stanza, you'll set up a system that boots into runlevel 1, with boot messages shown on the screen. Make sure to label that stanza appropriately, so the option Single User Mode appears in the GRUB menu. To prove the result, reboot the system, check the menu, and boot into the Single User Mode option.

Password-protect that stanza using the techniques described in Lab 3. Reboot the system. If successful, when you select the Single User Mode option, the GRUB menu should prompt for the password that was just created.

Lab 5

Be careful with this lab. The steps may render this system unbootable, unless you understand the skills described in this chapter. There's always the risk that key configuration files will not be properly backed up, which means there's a risk of losing all data on the system. If you understand these risks, proceed with this lab.

This lab is based on the Ch5Lab5 script described earlier. If you followed the instructions at the beginning of this section, the script should be available in your /root directory. Navigate to that directory and take the following steps:

1. Log into the root account. If you're not already there, navigate to the /root directory. Execute the script for this lab with the ./Ch5Lab5 command.

2. Reboot the system.

3. When you see the grub> prompt, use the skills described in this chapter to identify the drive and partition with the /boot directory. Hint: the stage1 file will still exist in that directory.

4. Where applicable, take advantage of the command completion features at the grub> prompt. That's especially useful with the kernel / and initrd / commands.

5. Don't forget, the kernel is first booted in read-only mode, as specified by the ro option.

6. Remember that the top-level root directory is specified by the root directive with the kernel command.

7. You don't have to remember the UUID associated with the top-level root directory; in fact, it would be remarkable if you did. Just use the partition or volume device file such as /dev/vda1. (Hint: in the default installation created in Chapter 1, the partition device file associated with the top-level root directory is not /dev/vda1.)

8. After entering the location of the Initial RAM disk, run the boot command at the grub> prompt.

9. If your efforts are successful, the system will boot normally. In the answer section, you'll see how to restore the backed-up GRUB configuration file.

10. If your efforts are not successful, boot the system from the installation DVD or the network boot CD and select Rescue Installed System as described in the main body of the Chapter.

Lab 6

This lab is focused on active terminals. Normally, Linux includes six active terminals. If a GUI is installed and active with a graphical display manager, that system is run in place of the first active terminal. To review, you can switch between active terminals with the ALT key and the function key associated with a terminal number, such as ALT-F1. If in the GUI, you'll need to add the CTRL key to the combination.

1. Back up the current versions of the /etc/sysconfig/init and /etc/init/start-ttys.conf configuration files. A logical location is the current user's home directory. If you make a serious mistake, you'll be able to restore the system from the backup. In the worst case, you'll be able to restore these files from backup by booting into single-user mode, as described in Lab 1 and in the body of the chapter.

2. Now limit the active consoles to terminals 1 and 2.

3. If successful, you'll be able to access only those two terminals on the local system. Can you restore the original configuration?

Lab 7

While there's no longer a separate troubleshooting section on the RHCSA or RHCE exams, troubleshooting skills are still useful on the exam—and on the job. So this lab will help you set up a troubleshooting scenario.

This lab is based on the Ch5Lab7 script, similar to the Ch5Lab5 script described earlier. If you followed the instructions at the beginning of this section, the script should be available in your /root directory. Navigate to that directory and take the following steps:

1. Log into the root account. If you're not already there, navigate to the /root directory. Execute the script for this lab with the ./Ch5Lab7 command.

2. Deactivate the current network device. If it's eth0, run the ifdown eth0 down command. Substitute for eth0 as needed. (The device may be some other file like eth1 or System_eth0, as shown in the output to the ifconfig -a command.)

3. Restart networking with the /etc/init.d/network restart command. What happens? Do you have a network connection?

4. If you don't see the problem right away, go through the different configuration files discussed in the chapter. You may need to make a couple of changes to a configuration file.

5. When you've identified and fixed the problem in the appropriate configuration file, you'll be able to run the /etc/init.d/network restart command and see successful messages. If a “Device not managed by NetworkManager” message appears, you may also need to run the ifup eth0 command.

6. If you still have problems, look at the file in the /root/backup directory. To restore the system, copy that file to the /etc/sysconfig directory.