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OPS235 Lab 4 - CentOS6

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{{Admon/caution|THIS IS AN OLD VERSION OF THE LAB|'''This is an archived version. Do not use this in your OPS235 course.'''}}
=Logical Volume Management (Continued) and User / Group Management=
In this lab you're going to learn how to:
:* Add a virtual hard disk and expand your vm's existing file system using LVM
:* Administer (add, remove, modify) users on a Linux system.
:* Save time while adding new users using a template of start-up files.
:* Create and manage groups on a Linux system.
== Required Materials (Bring to All Labs) ==
* CentOS 6.5 x86_64 Live DVD
* CentOS 6.5 x86_64 Installation DVD1
* SATA Hard Disk (in removable disk tray)
* USB Memory Stick
* Lab Logbook
* Completion and Instructor "Sign-off" of Lab 2: [[OPS235 Lab 3 - CentOS6]]
==Linux Command Online Reference==
Each Link below displays online manpages for each command (via []):
{|width="100%" cellpadding="5"
|'''LVM Information Utilities:'''
|'''LVM Management Utilities:'''
|'''Additional Utilities:'''
|- valign="top"
*[ vgs]
*[ lvs]
*[ pvs]
*[ vgdisplay]
*[ lvdisplay]
*[ pvdisplay]
*[ system-config-lvm] (Tutorial)
*[ lvextend]
*[ resize2fs]
*[ lvcreate]
*[ lvreduce]
*[ pvcreate]
*[ vgextend]
*[ mount]
*[ umount]
*[ useradd]
*[ userdel]
*[ usermod]
*[ groupadd]
*[ groupdel]
==Resources on the web==
Additional links to tutorials and HOWTOs:
:* [[Logical Volume Management]] ('''Note:''' It is recommended to return to this guide as a reference when performing the next several investigations)
:* [ Linux File Systems (ext2/ext3/ext4)]
:* [ Partitioning with fdisk]
:* [ Mounting / Unmounting File-systems]
:* [ UID and GID explained]
= Storage Setup (prior to starting Lab 4) =
At this point, having completed [[OPS235 Lab 3 - CentOS6|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 />
LV VG Attr LSize
lv_home vg_centos3 -wi-ao---- 1.00g
lv_root vg_centos3 -wi-ao---- 1410.54g 00g
lv_swap vg_centos3 -wi-ao---- 992.00m
PV VG Fmt Attr PSize PFree /dev/vda3 vg_centos3 lvm2 a-- 14.51g 02.54g /dev/vdb vg_centos3 lvm2 a-- 2.00g 02.00g
* '''c6host (i.e. "disk pack")'''
== Resources ==
'''Please read this page to get an overview of LVM:'''<br [http:/><br />('''Note:''' It is recommended to return to this guide as a reference when performing the next several investigations)zenit.senecac.on.<br ca/wiki/><br index.php/>* [[Logical_Volume_Management Logical Volume Management]]
It is recommended to open another window(eg. '''right-click''', '''open in new tab or window''') to make reference to view LVM commands as you perform investigations 1 to 3.
== 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 ''fedora2centos2'' VM in '''lab3'''), but you will using command-line tools in the '''fedora 3centos3''' VM. Since the fedora3 centos3 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:
## :: a. Determine the current LVM configuration using the <code>pvs</code>, <code>vgs</code>, and <code>lvs</code> commandcommands.## :: b.Grow the home filesystem to 2G using the command <code>lvextend</code> and <code>resize2fs</code>.## :: c.Create a new 2G LV containing an ext4 filesystem and mount it at /archive (use <code>mkdir</code>, <code>lvcreate</code>, <code>mkfs</code>, <code>mount</code>, edit the file <code>/etc/fstab</code>(read the resource: [] ), and then reboot to confirm automatic mount).## :: d.Copy the contents of <code>/etc</code> into <code>/archive</code>.## :: e.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 VGusing Command-Line Tools? =='''# Add an additional 2 GB virtual disk to your ''<u>fedora1centos1</u>'' system, and we will 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 Do the ''Adding new virtual hardware'' window that appears, select a Hardware Type rest of ''"storage"'' and click ''"Forward"''.# Make certain option "Managed or other existing storage" is selected. Click on this investigation in the ''Browse'' button, then click on ''New Volume''command line.# 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).
# Read the resource [ /fdisk_partitioning.html Partitioning with fdisk] to learn how to properly create a partition with the fdisk command.# Use fdisk to partition /dev/vdb with a Linux 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/Mark ''vdb1''</code>as a physical volume usable by LVM.# 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/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 fdisk to manage storage on my disk pack? =='''On your <u>f17hostc6host</u> (i.e. "disk pack"), using your choice of the GUI and/or command-line tools:'''# Create a new partition or logical partition drive ('''NOT a logical volume!''') - minimum 5G, leaving at least 10G free space in the extended partition.# Add Format that partition as (i.e. put a PV into the existing VG (using the commands you used in the previous investigationfilesystem on it).# Grow the root filesystem Make sure it's mounted automatically on a mountpoint of your choosing (easiest is to fill the available spacecreate a new directory for a mountpoint).  
= User/Group Management =
== Investigation 5: Adding users ==
{{Admon/note|Use f17hostcentos1|Perform these steps in the '''f17hostcentos1''' 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.
# Be sure to record your observations in your lab notes.
{{Admon/note|Use fedora3centos3|Perform these steps in the '''fedora3centos3''' virtual machine.}}# Add your matrix account user to '''fedora3centos3'''.
== Investigation 6: Managing Groups ==
{{Admon/note|Use fedora1centos1|Perform these steps in the '''fedora1centos1''' virtual machine.}}
# Read the man page for the groupadd and groupdel commands.
#* 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.
== Investigation 7: Deleting users ==
{{Admon/note|Use fedora1centos1|Perform these steps in the '''fedora1centos1''' virtual machine.}}
# Read the man page for the userdel command. Note which option automatically removes the users home directory when that user is deleted.
== Investigation 8: Modifying users ==
{{Admon/note|Use fedora1centos1|Perform these steps in the '''fedora1centos1''' 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 ''fedora1centos1'' -- you now have two virtual disks on ''fedora1centos1'', and therefore two image files, and therefore will need two backup files.}}
Arrange proof of the following on the screen:
# Two PVs on '''fedora1centos1'''.# Separate <code>/home</code> filesystem (on an LV) in '''fedora1centos1'''.<!-- # Unnecessary accounts and groups have been removed on '''fedora1'''. --># Account created on '''fedora3centos3''' matching your Matrix account.
# List contents of '''/etc/group''' file (ops235 group).
# List contents of '''/etc/passwd''' file (created accounts).

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