View source for OPS235 Lab 4 19

[[Category:OPS235]][[Category:OPS235 Labs]]
{{Admon/caution|THIS IS AN OLD VERSION OF THE LAB|'''This is an archived version. Do not use this in your OPS235 course.'''}}
=LVM Continued / User &amp; Group Management=

In this lab, we will continue to use LVM in order to make our file system(s) more flexible. We will also learn how to manage user accounts (eg. creation and removal). We will also learn how to setup accounts that automatically contain pre-existing files to make account creation easier for the system administrator. We will also learn how to manage groups to allow users to share resources (eg. files).

==Introduction==

In this lab you're going to:

:* Learn how to grow file systems by adding virtual hard disks to your VMs.
:* Learn how to manage user accounts and groups for sharing files.

== Required Materials (Bring to All Labs) ==

* Fedora 19 DESKTOP LIVE CD  (Useful as a rescue disk)
* Fedora 19 x86_64 FULL 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/ http://linuxmanpages.com]):

{|width="100%" cellpadding="5"
|'''LVM Information Utilities:'''
|'''LVM Management Utilities:'''
|'''Additional Utilities:'''
|- valign="top"
|
*[http://linuxmanpages.com/man8/vgs.8.php vgs]
*[http://linuxmanpages.com/man8/lvs.8.php lvs]
*[http://linuxmanpages.com/man8/pvs.8.php pvs]
*[http://linuxmanpages.com/man8/vgdisplay.8.php vgdisplay]
*[http://linuxmanpages.com/man8/lvdisplay.8.php lvdisplay]
*[http://linuxmanpages.com/man8/pvdisplay.8.php pvdisplay]
|
*[http://www.centos.org/docs/5/html/Deployment_Guide-en-US/s1-system-config-lvm.html system-config-lvm] (Tutorial)
*[http://linuxmanpages.com/man8/lvextend.8.php lvextend]
*[http://linuxmanpages.com/man8/resize2fs.8.php resize2fs]
*[http://linuxmanpages.com/man8/lvcreate.8.php lvcreate]
*[http://linuxmanpages.com/man8/lvreduce.8.php lvreduce]
*[http://linuxmanpages.com/man8/pvcreate.8.php pvcreate]
*[http://linuxmanpages.com/man8/vgextend.8.php vgextend]
|}

==Resources on the web==

Additional links to tutorials and HOWTOs:
'''Please read this page to get an overview of LVM:'''<br /><br />
:* [[Logical Volume Management]] ('''Note:''' It is recommended to return to this guide as a reference when performing the next several investigations)


= Storage Setup (prior to starting Lab 4) =

At this point, having completed [[OPS235 Lab 3|Lab 3]] you should have <u>roughly</u> the following disk storage setup:<br />
('''Note:''' These results are output from the '''vgs''', '''lvs''', and '''pvs''' commands within each virtual machine. You will be using these commands in the following lab investigations)<br /><br />

* '''fedora1'''

  This VM has a GUI and no free space in the VG.
 
  VG         #PV #LV #SN Attr   VSize VFree
  vg_fedora1   1   2   0 wz--n- 9.80G    0
 
  LV      VG         Attr   LSize  
  lv_root vg_fedora1 -wi-ao   8.83G                                     
  lv_swap vg_fedora1 -wi-ao 992.00M                                     
 
  PV         VG         Fmt  Attr PSize PFree
  /dev/vda2  vg_fedora1 lvm2 a-   9.80G    0

* '''fedora2'''

  This VM has a GUI and free space in the VG.
 
  VG         #PV #LV #SN Attr   VSize VFree
  vg_fedora2   1   3   0 wz--n- 14.80G 4.07G
 
  LV      VG         Attr   LSize   
  lv_home vg_fedora2 -wi-ao    1.95G                                     
  lv_root vg_fedora2 -wi-ao    7.81G                                     
  lv_swap vg_fedora2 -wi-ao  992.00M                                     
 
  PV         VG         Fmt  Attr PSize PFree
  /dev/vda2  vg_fedora2 lvm2 a-   14.80G 4.07G

* '''fedora3'''

  This VM has no GUI installed.
 
  VG         #PV #LV #SN Attr   VSize VFree
  vg_fedora3   1   3   0 wz--n- 9.80G 3.83G
 
  LV      VG         Attr   LSize  
  lv_home vg_fedora3 -wi-ao   1.00G                                     
  lv_root vg_fedora3 -wi-ao   4.00G                                     
  lv_swap vg_fedora3 -wi-ao 992.00M                                     
 
  PV         VG         Fmt  Attr PSize PFree
  /dev/vda2  vg_fedora3 lvm2 a-   9.80G 3.83G

* '''f19host (i.e. "disk pack")'''

  Four PVs, minimum VG size 60G
  Single filesystem on vg_main/root, size 50G
  At least 10G available space in VG
 
  20% of disk space unallocated to any partition (min 15G)

= Logical Volume Management (Continued) =

{{Admon/note|Recovering VMs|'''Most of these investigations will take place in you virtual machines.''' If you make a significant mistake, your virtual machine may not boot. Remember that you created backups of your virtual machines in Lab 3, and you can '''restore them if something goes wrong'''.}}

== Resources ==

'''Please read this page to get an overview of LVM:'''<br /><br />('''Note:''' It is recommended to return to this guide as a reference when performing the next several investigations).<br /><br />
* [[Logical Volume Management]]


== Investigation 1: How are LVMs are managed using Command-Line Tools  ==
# You are going to repeat the same LVM management operations (as your did with the ''fedora2'' VM in '''lab3'''), but you will using command-line tools in the '''fedora 3''' VM. Since the fedora3 VM only operates in command-line mode, you will need to refer to the '''"Logical Volume Management"''' link above.
# Write down the exact commands used at each step, and record appropriate command output:
## Determine the current LVM configuration using the <code>pvs</code>, <code>vgs</code>, and <code>lvs</code> command.
## Grow the home filesystem to 2G using the command <code>lvextend</code> and <code>resize2fs</code>.
## Create a new 2G LV containing an ext4 filesystem and mount it at /archive (use <code>lvcreate</code>, <code>mkfs</code>, <code>mount</code>, edit the file <code>/etc/fstab</code>, and then reboot to confirm automatic mount).
## Copy the contents of <code>/etc</code> into <code>/archive</code>.
## Shrink <code>lv_archive</code> to 1G (use <code>umount</code>, <code>resize2fs</code>, <code>lvreduce</code>,  and <code>mount</code>)

== Investigation 2: How can a PV be added to an existing VG? ==
'''Add an additional 2 GB virtual disk to your ''<u>fedora1</u>'' system, and use it as an additional physical volume:'''
# Start <code>virt-manager</code>.
# Shutdown ''fedora1'' if it is running.
# Open the console window for ''fedora1''.
# Select the menu option View>Details.
# Click ''Add Hardware'' button at the bottom left-hand corner.
# In the ''Adding new virtual hardware'' window that appears, select a Hardware Type of ''"storage"'' and click ''"Forward"''.
# Make certain option "Managed or other existing storage" is selected. Click on the ''Browse'' button, then click on ''New Volume''.
# Give the new virtual disk file a name of <code>fedora1b</code>, a format of ''raw'', with a ''Max Capacity'' and ''Allocation'' of 2000 MB. Click ''Finish''.
# Select the new virtual disk file ''fedora1b.img'' and click ''Choose Volume''.
# Select a device type of ''Virtio Disk''.
# Finish creating the new virtual disk by clicking ''Forward'' and then ''Finish''.
# Boot the system. You should now have both <code>/dev/vda</code> and <code>/dev/vdb</code>.
# Record the size of the volume group and the amount of free space (Hint: use a command that you learned in a previous lab).
# Partition /dev/vdb with a single partition that fills the whole disk.
# Check the messages printed when <code>fdisk</code> exits -- you may need to reboot the system in order for the new partition table to take effect.
# Run this command to format the physical volume: <code>pvcreate /dev/''vdb1''</code>
# Add the new physical volume to the existing volume group: <code>vgextend ''nameOfVolumeGroup'' /dev/vdb1</code>
# Verify that the volume group is larger and has more free space.

{{Admon/note|Think!|The next part of this investigation requires some research, thought, and creativity.}}
'''Using that additional space, create a separate filesystem for <code>/home</code>:'''
# Create the logical volume <code>lv_home</code> (1G ext4)
# Find a way to move the contents of <code>/home</code> onto it.
# Change your system configuration so that the new filesystem is mounted on <code>/home</code> from now on.

{{Admon/tip|SELinux relabelling may be required|Your system may report that the files are not present in the new /home filesystem when they are clearly there. This is due to the Security-Enhanced Linux system (SELinux) preventing access to the files, because the files were tampered with (moved) and are no longer recognized as home directory content. You can fix this problem by restoring the file context labels so that SELinux accepts the files as valid home directory content: <code>restorecon -r /home</code>}}

== Investigation 3: How can I use LVM to manage storage on my disk pack? ==
'''On your <u>f19host</u> (i.e. "disk pack"), using your choice of the GUI and/or command-line tools:'''
# Create a new logical partition ('''NOT a logical volume!''') - minimum 5G, leaving at least 10G free space in the extended partition.
# Add that partition as a PV into the existing VG (using the commands you used in the previous investigation).
# Grow the root filesystem to fill the available space.



= User/Group Management =

== Investigation 4: The /etc/passwd file ==

# Look at the /etc/passwd file.
# Make note of the contents of that file.
# Read about the file: http://linux.die.net/man/5/passwd 
# Make sure you know what information each field contains.
# Why do you think there are so many users?
# Look at the names of the users. What do you think these user names represent? Are they people?
# What is the numeric user ID (UID) of the root user?
# The user IDs of real users (people) are different from the user IDs of system accounts. What is the pattern?

== Investigation 5: Adding users ==

{{Admon/note|Use f19host|Perform these steps in the '''f19host''' system. Due to a configuration issue, these steps may not work normally in the fedora1 virtual host (previous versions of this lab used fedora1 for this investigation).}}

# Read the man page for the useradd command.
# 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.
# Grep the /etc/passwd file for each of the new users.
#* 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?
# 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. 
# Create two new dummy users, ops235_1 and ops235_2.
# 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: <code>touch foo</code>
#* 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?
# Be sure to record your observations in your lab notes.

{{Admon/note|Use fedora3|Perform these steps in the '''fedora3''' virtual machine.}}
# Add your matrix account user to '''fedora3'''.

== Investigation 6: Managing Groups ==

{{Admon/note|Use fedora1|Perform these steps in the '''fedora1''' virtual machine.}}

# Read the man page for the groupadd and groupdel commands.
# Note which option allows you to set the Group ID number (GID) when you create a new group.
# Examine the file /etc/group
#* Which values of GID are reserved for system accounts?
#* Which values of GID are reserved for non-system user accounts?
#8 What is the lowest available GID number for non-system users?
#* What is the default group name of a new user?
#* Add a new group named ops235 with a GID of 600.
#* 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 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.

== Investigation 7: Deleting users ==

{{Admon/note|Use fedora1|Perform these steps in the '''fedora1''' virtual machine.}}

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

# Delete the user ops235_1 using the command <code>userdel ops235_1</code>
# Delete the user ops235_2 using the same command with the option which removes the home directory of the user.
# Check the contents of the /home directory. What do you notice?
# Check the contents of the /etc/group directory. What do you notice?

Be sure to record your observations in your lab notes.


== Investigation 8: Modifying users ==

{{Admon/note|Use fedora1|Perform these steps in the '''fedora1''' virtual machine.}}

# Read the man page for the usermod command. Note which options change the user's full name, primary group, supplementary groups, and shell.

# Add each of your new users to the group ops235 (in other words, add ops235 to each user as a supplementary group).
# Examine <code>/etc/group</code>. What has changed?
# 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 <code>/etc/passwd</code> file. What has changed?
# Be sure to record your observations in your lab notes.


<!-- == Investigation 13: Security Tip: Removing Unnecessary Users and Groups ==

{{Admon/note|Use fedora1|Perform these steps in the '''fedora1''' virtual machine.}}

The default Linux distribution installs many users and groups to the system for the purpose of running various services. You will rarely, if ever, need to run all of these services on a single server, and some are actually obselete for most systems. Servers tend to be specialized, for both performance and security reasons. For example, a web server would probably not be running as an email server and file server at the same time. While having all the possible user accounts installed by default makes it easier to set services up, it also increases the complexity of the machine. The more complex a system is, the more places it can fail, and hence its security is lessened. Therefore, we can increase our server's security by removing unnecessary users.

There is no set list of users we can safely remove. The requirements of each system varies greatly, and it is up to the administrator to know these requirements, and understand which accounts can be removed. However, the list we provide here can usually be removed, unless their services are specifically required.

# Before attempting the following, make backup copies of your /etc/passwd and /etc/group files, in case we delete a user or group that is essential to our system's operation.
# Carefully remove the following users from your system, if they exist: 
#* games
#* gopher
#* lp (if no printer is installed)
#* news
#* nfsnobody
#* nscd (if not using nscd)
#* uucp
# Carefully remove the following groups from your system, if they exist: 
#* games
#* gopher
#* lp (if no printer is installed)
#* news
#* nfsnobody
#* nscd (if not using nscd)
#* uucp -->

= Completing the lab =

{{Admon/important|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:
# Two PVs on '''fedora1'''.
# Separate <code>/home</code> filesystem (on an LV) in '''fedora1'''.
<!-- # Unnecessary accounts and groups have been removed on '''fedora1'''. -->
# Account created on '''fedora3''' matching your Matrix account.
# List contents of '''/etc/group''' file (ops235 group).
# List contents of '''/etc/passwd''' file (created accounts).
# Fresh backup of the virtual machines.

= Preparing for the Quizzes =

# What is a VG? PV? LV? 
# What is the total size of the "main" VG on your system?
# How do you create a LV?
# How do you delete an LV?
# How would you add the disk partition <code>/dev/sdb7</code> to your volume group "main"?
# How would you increase the size of the root filesystem by 50 MB?
# What is the purpose of <code>/etc/fstab</code>?
# What is the purpose of <code>/etc/shadow</code>?