3.1 The CLS Source DirectoryIndex

All references to the “Source Directory” below are to the CLS directory ~idallen/cst8207/13f/assignment14/ and that name starts with a tilde character ~ followed by a userid with no intervening slash. The leading tilde indicates to the shell that the pathname starts with the HOME directory of the account idallen (seven letters).

3.2 Commands, topics, and features coveredIndex

Review course notes Booting and GRUB.

Use the on-line help (man command) for the commands listed below for more information.

• chkconfig – display or change Run Level information and services
• grub – GRand Unified Bootloader (legacy version 0.9x - not the Version 2 GRUB numbered 1.9x). The man page is useless. See this instead: GRUB manual
• runlevel – display previous and current Run Level
• telinit – change Run Levels
• uname – print system information: display system name, kernel release and version number, machine, processor, and O/S type
• /etc/inittab – documentation on Run Levels; contains the default Run Level
• /boot/grub/grub.conf – the GRUB Legacy (version 1) configuration file

3.3 Correct user, command lines, and command outputIndex

• Most of the commands in this assignment require root privilege. Use the sudo command to run individual commands as root – don’t use a root subshell.

• If you start a root subshell (not recommended – use sudo instead), your prompt will tell you if you are the root user by changing to include a # character instead of a $ character. You can also use the commands id or whoami to show your current userid.

• Some answers require you to record command lines. Do not include the shell prompt with your command lines. Give only the part of the command line that you would type yourself.

• Make sure you know the difference between a command line (which is what you type into the shell) and command output (which is what the command displays on your screen). Pay attention to whether the question asks you to record the command line or the command output.

3.4 Backup and RecoveryIndex

1. Take a snapshot of your virtual machine before you begin each section of this lab so that you can recover back to the snapshot if needed. You can delete the unused snapshots if everything works well.

2. Are you keeping an external backup copy of all your coursework (including your virtual machines) somewhere? You should be!

3.5 Use a remote login, not the VMware consoleIndex

I recommend that once you have booted your CentOS VM, you connect to it and work using a remote login session (e.g. ssh or PuTTY) where copy-and-paste works and where you can have multiple simultaneous connections into the VM. The VMware console is not friendly.

3.6 The Answer File answer.txtIndex

Where you are required to record or save a command line or its output into The Answer File, do the command and then copy and record the command line or its output as a separate line into an answer.txt file in your CentOS assignment14 directory. You will be told how many lines to save in the file.

If you can’t answer a question, leave a blank line in this answer file. (The vim option :set number may be useful to you as you edit.)

You can use either nl or cat -n to show the contents of a file with line numbers, to make sure each answer is on its correct line number.

4.1 Set UpIndex

1. Create your assignment14 directory on the CLS in the usual place.

2. Create your sysadmin account assignment14 directory on your CentOS VM in the usual place (not in the root account!).

   This CentOS directory is the base directory for all pathnames in this assignment. Store your files and answers here on CentOS.

3. Before you begin this assignment, create a snapshot of your CentOS Virtual Machine, as mentioned above.
   • Enter a comment explaining where and when you took this snapshot.
   • You can restore back to this snapshot if anything goes wrong.

4. Run the Checking Program to verify your work so far.

4.2 Booting into single-user mode (changing forgotten root password)Index

Review Booting and GRUB.

This section depends on a successful CentOS Virtual Machine installation, including a working GRUB menu.

To change a forgotten root password or do maintenance on the system that requires it to be quiescent, you can boot your system in a restricted single-user mode that does not start many system daemons and goes directly into a root shell prompt on the system console without requiring a password.

The system should not be left in single-user mode; many things are not started. You may not even be able to log-in remotely in single-user mode.

1. View your CentOS GRUB configuration file and look at the kernel line in that file. Note all the options used on the kernel line; you will see them again soon.
   • Record on Line 1 in The Answer File the Linux absolute pathname of this GRUB configuration file.

2. Record on Line 2 in The Answer File the kernel option keyword used in booting a machine single-user (maintenance mode). (one word)

3. Safely reboot your CentOS VM into the GRUB menu.

4. When the boot process begins, if you correctly disabled the hiddenmenu command in GRUB, you will boot directly to the GNU GRUB menu where you should see a one-line list of CentOS systems to boot and at the bottom a 30 second countdown in progress.
   • Interrupt the countdown by pressing an arrow key. (If you didn’t disable hiddenmenu, when the countdown is interrupted your system should display the one-entry GRUB menu.)

CentOS 6 GRUB Menu

5. Now, just as the GRUB menu instructions tell you, to modify the kernel arguments you press just the single letter a – just the letter key, no [Enter] key!
   • After pressing a you will see your cursor on a line that ends with the same kernel arguments you viewed earlier in the configuration file.
   • You can use the [Home] key to zoom to the left end of the kernel options line, and the [End] key to zoom to the right.

CentOS 6 Kernel Options

6. Modify this kernel options line so that the system will boot single-user. (Add the correct kernel option keyword to the end of the line.)
   • As the instructions say, push [Enter] to accept your changes and directly boot the system using these new kernel options.
   • These changes to the kernel options are not saved back into the configuration file – they are only in effect for this boot menu.
   • (If you wanted to abandon your changes and leave the menu entry unmodified, you would have used the Escape key, as it says.)
7. The system should come up in single-user (maintenance) mode with a root shell prompt. (If you get a login prompt, you didn’t use the right kernel option keyword. Reboot and try again.)
   • You can perform any root function at this prompt, including changing passwords (even the root password).
   • Often single-user mode has no networking enabled and only a minimal number of file systems mounted.

8. From the single-user shell, place a full list of all processes for all users, BSD format, text user name (not numeric UID), full wide listing (not truncated at all), into a psbsd-single.txt file. (All assignment answer files must be saved in your sysadmin CentOS assignment14 directory.) The output should be approximately 52 lines and 4KB. All the processes will be owned by root. The first two lines will look similar to this:

   USER  PID %CPU %MEM  VSZ   RSS TTY  STAT START   TIME COMMAND
   root    1  2.5  0.5 2900  1368 ?    Ss   16:35   0:01 /sbin/init

9. Use the command that displays the previous and current Run Level (two words on one line) and record this line of output as Line 3 in The Answer File.

10. Leave single-user mode and let the system finish booting into full multi-user mode. The login prompt should appear on the console.
    • Leaving single-user mode does not mean rebooting the machine. Do not reboot or shut down the machine.

11. Log in as your sysadmin account (optionally use an SSH login, not the terrible console window) and repeat the command that displays the previous and current Run Level and save the output as Line 4 in The Answer File (two more words on one line).

12. Check your work using the Checking Program.

4.3 Using a different GRUB configuration fileIndex

Review Booting and GRUB.

You can select a different GRUB configuration file at boot time.

1. Record the number of lines in a standard Linux boot menu entry as Line 5 in The Answer File (one number).

2. In your running CentOS VM, copy the current GRUB configuration file to a new file named myconfig in its same grub directory.
   • Record the Linux absolute pathname of the new file as Line 6 in The Answer File.
3. Edit the myconfig file:
   1. On the title line of the only boot menu entry in the file, change the word CentOS to MY OWN CentOS
   2. Save the myconfig file.

4. Compare the current GRUB configuration file with the new myconfig GRUB configuration file. The new file should have two more words. A file difference using the diff command should show the one line change:

   $ diff grub.conf myconfig
   14c14
   < title CentOS (2.6.32-358.el6.i686)
   ---
   > title MY OWN CentOS (2.6.32-358.el6.i686)

4.3.2 Run the new GRUB configuration fileIndex

11. When you have successfully previewed your new GRUB configuration file above and you see your MY OWN CentOS menu entry, as shown above, you are ready to try your new file in the real GRUB boot process:
    1. Safely reboot your CentOS VM into the standard GRUB menu (the one that doesn’t have your changes).
    2. As you did before, interrupt the GRUB countdown timer.
    3. Follow the GRUB directions on your screen and type the correct letter key to start up a GRUB command line. GRUB will then prompt with the usual grub> prompt.
    4. At the grub> prompt, use the exact same configfile line you used earlier to select your new myconfig GRUB configuration file. (In this boot loader version of GRUB, TAB completion now works for both GRUB command names, disk names, partition names, and file names. Use TAB to help you type the correct GRUB command line.)
    5. When you load your new configuration file inside the boot loader version of GRUB, you should see your MY OWN CentOS menu entry, like this:

CentOS 6 myconfig configuration file

12. Let the time out expire to boot your system, or use the [Enter] key.

13. Check your work using the Checking Program.

4.4 Configure a second GRUB boot menuIndex

Your current CentOS GRUB configuration file contains only a single boot menu entry for one Linux kernel. We will now create a new GRUB configuration file with a second boot menu entry.

1. In your running CentOS VM, copy your myconfig configuration file to a new file named newconfig in its same grub directory.
   • Record the Linux absolute pathname of the new file as Line 8 in The Answer File.
2. Edit the newconfig file to create a second boot menu entry that will boot the machine single-user as follows:
   1. Copy the existing four-line boot menu entry in the file and create a new four-line boot menu entry below it. (Copy and paste four lines in the file. In vim put your cursor on the first line to copy and type 4yyP.)
      • The new four-line boot menu entry must start out as an exact copy of the original four-line boot menu entry.
      • Do not make any changes to the first four-line boot menu entry.
   2. On the title line of the second boot menu entry change the word CentOS to single user CentOS
   3. In the second boot menu entry add the kernel option to boot in single-user mode, just as you did earlier when booting single-user from the live GRUB menu.

   4. Save your changes. Your new newconfig configuration file will now be four lines longer than the myconfig file:

      $ wc -l myconfig newconfig 
        17 myconfig
        21 newconfig

3. To make sure your newconfig file works before you reboot, preview your configuration file changes using the grub utility run from the shell as you did before. You should see this two-line menu as preview output when you load your newconfig configuration file into GRUB:

       GNU GRUB  version 0.97  (640K lower / 3072K upper memory)
   -------------------------------------------------------------------
    0: MY OWN CentOS (2.6.32-358.el6.i686)
    1: MY OWN single user CentOS (2.6.32-358.el6.i686)
   -------------------------------------------------------------------

4. When you have the preview working, safely reboot and run your new GRUB newconfig configuration file using the same method as you did earlier to run tye myconfig file.
   • Make sure you see two choices in your GRUB menu now:

CentOS 6 newconfig configuration file

5. Select the single-user choice. It must boot the machine into the single-user root shell with no password required.

6. Leave single-user mode and continue the boot process into standard multi-user mode (with a login prompt).

7. In multi-user mode, log in as your sysadmin account (optionally use an SSH login, not the terrible console window) and check your work so far using the Checking Program.

4.5 Changing System V Run Levels and ServicesIndex

See the section on Legacy Run Levels and Services in the Booting and GRUB page. As with most system maintenance activities, you will need to use the sudo command to run the privileged commands in this section.

1. If not already logged in, log in to the CentOS VM console (not via SSH) as your ordinary (non-root) sysadmin account.
   • You will see console messages if you are logged in to the console, which you will not see using an SSH terminal connection.

2. Use a command to list all services and all run level information into file chkconfig-before.txt in your CentOS assignment14 directory. It should be approximately 22 lines. Two of the lines should look like this:

   ntpdate         0:off   1:off   2:off   3:off   4:off   5:off   6:off
   postfix         0:off   1:off   2:on    3:on    4:on    5:on    6:off

3. Use the same command name to enable (turn on) the NTP Date service only in Run Level 4 (a normally unused Run Level in CentOS).

4. Use the same command name to disable (turn off) the above Postfix Mail Service service in Run Level 4.

5. Save a second listing of all services and all run levels into file chkconfig-after.txt in your CentOS assignment14 directory. It should still be approximately 22 lines. Two of the lines should now look like this:

   ntpdate         0:off   1:off   2:off   3:off   4:on    5:off   6:off
   postfix         0:off   1:off   2:on    3:on    4:off   5:on    6:off

6. Use the diff command to compare the before listing file with the after listing file. Only two lines should have changed.

7. Run a command to show a full list of all processes for all users, BSD format, text user name (not numeric UID), full wide listing (not truncated at all) and search for any lines containing the string postfix.
   • You will see about three or four lines.
   • Save those three or four lines into a postfix.txt file.

8. Record as Line 9 in The Answer File the Linux absolute pathname of the system configuration file that gives the default Run Level for your CentOS system.

9. Record as Line 10 in The Answer File the one line from the above system configuration file that sets the default Run Level for your CentOS system. (Hint: It’s the only non-comment line in the file!)

10. Use a command to confirm that your current Run Level is the same as the CentOS default Run Level. (This should be true unless you are running in single-user mode, which you should not be.)

11. On the system console, use a command to change from the current Run Level (which should be the default) to Run Level 4. You will see (only if logged in on the console) various status messages about services that stop and start:
    • The Postfix service will announce that it is shutting down.
    • The lvm2-monitor service will complain that it is too dangerous to shut down.
    • The udev event manager will retrigger some events.
    • The ntpdate service will try to synchronize the time, and fail.

12. Use the command that displays the previous and current Run Level (two words on one line) and record this line of output as Line 11 in The Answer File.

13. In a system log file, find the reason that the ntpdate service did not work:
    • How do you know which System Log Files were modified most recently? Those log files are the files you should look in for the log message.
    • The message from ntpdate talks about a socket being in use.
    • When you find the right log file name, record the Linux absolute pathname of the correct log file as Line 12 in The Answer File.
    • Record this last ntpdate log message as Line 13 in The Answer File.
14. Run a command to show a full list of all processes for all users, BSD format, text user name (not numeric UID), full wide listing (not truncated at all) and again search for any processes running as the postfix userid.
    • No processes running as the postfix userid will be found. (You might see a process run by you, searching for postfix.)
15. On the system console, use a command to change from the current Run Level 4 back to the CentOS system default Run Level. You will again see (only if logged in on the console) various status messages about services that stop and start:
    • The udev event manager will retrigger some events.
    • The Postfix service will announce that it is starting.

16. Use the command that displays the previous and current Run Level (two words on one line) and record this line of output as Line 14 in The Answer File.

17. Confirm that the postfix processes are again running.

18. Check your work using the Checking Program.

4.6 Manually Starting/Stopping ServicesIndex

See the section on Starting and Stopping Services in the Booting and GRUB page. As with most system maintenance activities, you will need to use the sudo command to run the privileged commands in this section.

1. Make sure your system is running as the default CentOS Run Level.

2. Use a command to ask for the service status of the postfix service:
   • The output of the command will include the pid of the service and say that it is running.
   • Record the one line of output (with the pid) as Line 15 in The Answer File.
3. Use a command to stop the postfix service:
   • You will see one line of logging information saying: Shutting down postfix: [ OK ]
4. Use a command to ask for the service status of the postfix service:
   • The output of the command will say that the service is stopped.
   • Record the one line of output from the command as Line 16 in The Answer File. (Record the stopped output line from the status command, not the Shutting down logging information.)
5. Use a command to start the postfix service:
   • You will see one line of logging information saying: Starting postfix: [ OK ]
6. Use a command to try to start the ntpdate service:
   • You will see one line of logging information saying: [FAILED]
   • The system log file will tell you why it failed.

7. Check your work using the Checking Program.

4.7 Kernel Version Number (release number)Index

Your Linux kernel has a version number, as in “What version of the kernel are you running? I’m running version 2.6.32”.

Unfortunately, the command that prints system information, including the kernel version number, calls the number a kernel release number, because it uses the option name version to stand for the kernel compile date. When using this system information command to display the kernel version number, you must use the option for release.

1. Display only the version (release) of the Linux kernel that is running on CentOS (about 17-20 characters):
   • Record the command line you must use as Line 17 in The Answer File.
   • Record the one line of output for CentOS as Line 18 in The Answer File. (The output starts with the digit 2 on CentOS.)
   • Log in to the CLS find out what kernel it is running. Record the one line of output for the CLS as Line 19 in The Answer File. (The output starts with the digit 3 on the CLS – the CLS runs a newer kernel than CentOS.)
2. Check your work using the Checking Program.

4.8 When you are doneIndex

That is all the tasks you need to do.

Check your work a final time using the Checking Program and save the output as described below. Submit your mark following the directions below.

5.1 Part I - Fetch and CheckIndex

Do all the following steps on your CentOS Virtual Machine. Read through the whole list before you start typing anything. An example of what to type is given below the descriptions that follow.

1. Log in to CentOS using your system administrator (non-root) account.

2. Change to your existing CentOS assignment14 directory containing all your answer files for this assignment.

3. As shown below, use curl to get a copy of the Fetch program from the given URL into a file named do.sh.
   • Make sure you end up with a file named do.sh in your assignment14 directory.
   • Make sure the downloaded file is not a file of HTML and errors. It should start with #!/bin/sh and contain a few shell comments and commands, including another curl command.
   • You only need to download this Fetch program once per assignment.
4. As shown below, use sudo to run the do.sh script you just downloaded to CentOS, with the USER environment variable set to your own College/Blackboard/CLS account userid (do not use abcd0001).
   • You can run the do.sh script over and over to check your work.

5. This Fetch program will connect from CentOS to the CLS using your account name. It will copy files from CentOS to your assignment14 directory on the CLS. It will then run the checking program on the CLS to check your work. You will need to answer one question about your IP address, and then wait and type in your CLS password.

It will look something like this (use your userid, not abcd0001):

CentOS$ hostname
abcd0001

CentOS$ pwd
/home/abcd0001/CST8207-13F/Assignments/assignment14

CentOS$ echo "$USER"
abcd0001

CentOS$ curl -A mozilla http://teaching.idallen.com/cst8207/13f/notes/data/assignment14do.sh >do.sh
[... various download statistics print here ...]

CentOS$ sudo USER=$USER sh do.sh
---------------------------------------------------------------------------
abcd0001: FETCH version 2.  Connecting to CLS as USER='abcd0001' using ssh
---------------------------------------------------------------------------
abcd0001: Use local Algonquin IP cst8207-alg.idallen.ca [y/N]? n
abcd0001: Please wait; using ssh to connect to user 'abcd0001' on cst8207.idallen.ca ...
*** COURSE LINUX SERVER ***
abcd0001@cst8207.idallen.ca's password:         # enter your CLS password
---------------------------------------------------------------------------
idallen-ubuntu assignment14fetch_server.sh version 4 run by abcd0001.
Please wait; collecting info from abcd0001 Virtual Machine
---------------------------------------------------------------------------
VM files collected into CST8207-13F/Assignments/assignment14/abcd0001.tar.bz on CLS.
Now running checking program for abcd0001 on CLS:
[... checking program output appears here ...]

• You can use sudo to run the do.sh script over and over to check your work.
• You only need to run the curl line once, to get the do.sh script.

5.2 Part II - Check and SubmitIndex

When you are done with your assignment, you need to run the checking program one last time on the CLS and submit the output file, as follows:

Do all this one last time on the Course Linux Server (not on CentOS):

1. There is a Checking Program named assignment14check in the Source Directory on the CLS. Create a Symbolic Link to this program named check under your new assignment14 directory on the CLS so that you can easily run the program to check your work and assign your work a mark on the CLS. Note: You can create a symbolic link to this executable program but you do not have permission to read or copy the program file.

2. Execute the above “check” program on the CLS using its symbolic link. (Review the Search Path notes if you forget how to run a program by pathname from the command line.) This program will check your fetched CentOS work, assign you a mark, and display the output on your screen. (You may want to paginate the long output so you can read all of it.)

   Remember: The checking program does not fetch new files to the CLS from your CentOS VM. You must run the Fetch program on your CentOS VM to update the fetched files on the CLS so that the checking program can mark them on the CLS.

   You may run the “check” program as many times as you wish, to correct mistakes and get the best mark. Some tasks sections require you to finish the whole section before running the checking program at the end; you may not always be able to run the checking program successfully after every single task step.

3. When you are done with checking this assignment, and you like what you see on your screen, redirect the output of the Checking Program into the text file assignment14.txt under your assignment14 directory on the CLS. Use the exact name assignment14.txt in your assignment14 directory. Case (upper/lower case letters) matters. Be absolutely accurate, as if your marks depended on it. Do not edit the file. Make sure the file actually contains the output of the checking program!

4. Transfer the above assignment14.txt file from the CLS to your local computer and verify that the file still contains all the output from the checking program. Do not edit this file! No empty files, please! Edited or damaged files will not be marked. You may want to refer to your File Transfer notes.

5. Submit the assignment14.txt file under the correct Assignment area on Blackboard (with the exact name) before the due date. Upload the file via the assignment14 “Upload Assignment” facility in Blackboard: click on the underlined assignment14 link in Blackboard. Use “Attach File” and “Submit” to upload your plain text file.

   No word-processor documents. Do not send email. Use only “Attach File”. Do not enter any text into the Submission or Comments boxes on Blackboard; I do not read them. Use only the “Attach File” section followed by the Submit button. (If you want to send me comments about your assignment, use email.)

6. Your instructor may also mark the assignment14 directory in your CLS account after the due date. Leave everything there on the CLS. Do not delete any assignment work from the CLS until after the term is over!

7. Your instructor may also mark the files on your CentOS VM after the due date. Leave everything there on your CentOS VM. Do not delete any assignment work from the CentOS VM until after the term is over!

Use the exact file name given above. Upload only one single file of plain text, not HTML, not MSWord. No fonts, no word-processing. Plain text only.

Did I mention that the format is plain text (suitable for VIM/Nano/Pico/Gedit or Notepad)?

NO EMAIL, WORD PROCESSOR, PDF, RTF, or HTML DOCUMENTS ACCEPTED.

No marks are awarded for submitting under the wrong assignment number or for using the wrong file name. Use the exact name given above.

WARNING: Some inattentive students don’t read all these words. Don’t make that mistake! Be exact.

READ ALL THE WORDS. OH PLEASE, PLEASE, PLEASE READ ALL THE WORDS!