Difference between revisions of "OPS235 Lab 4 - CentOS7"

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= Storage Setup (prior to starting Lab 4) =
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= Software Package Management =
  
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At this point, having completed [[OPS235 Lab 3 - CentOS6|Lab 3]] you should have <u>'''roughly'''</u> the following disk storage setup:<br />
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== Investigation 1: How do you query the RPM database? ==
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('''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 />
 
  
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* '''centos1'''
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RPM maintains a database of installed software. This information is very useful to system administrators. In the previous lab you queried that database using RPM with the -q argument. When you query the RPM database, you can separately specify:
 +
:* Do an <u>operational task</u> on one or more packages (like installing or removing a package), using a '''select-option'''
 +
:* What <u>information</u> you want about those packages, using a '''query-option'''
  
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  This VM has a GUI and no free space in the VG.
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'''Perform the following steps:'''
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  VG        #PV #LV #SN Attr  VSize VFree
 
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  vg_centos1  1  2  0 wz--n- 9.80G    0
 
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  LV      VG        Attr  LSize 
 
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  lv_root vg_centos1 -wi-ao  8.83G                                   
 
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  lv_swap vg_centos1 -wi-ao 992.00M                                   
 
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  PV        VG        Fmt  Attr PSize PFree
 
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  /dev/vda2  vg_centos1 lvm2 a-  9.80G    0
 
  
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* '''centos2'''
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(Perform investigations 1 - 3 in your host machine (c6host)
  
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  This VM has a GUI and free space in the VG.
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# Using information from the man page for <code>rpm</code>, fill in this information:
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  VG        #PV #LV #SN Attr  VSize VFree
 
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  vg_centos2  1  4  0 wz--n- 19.51g 4.73g
 
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  LV      VG        Attr  LSize 
 
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  lv_archive vg_centos2 -wi-ao---- 1.00g                                           
 
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  lv_home    vg_centos2 -wi-ao---- 4.00g                                           
 
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  lv_root    vg_centos2 -wi-ao---- 7.81g                                           
 
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  lv_swap    vg_centos2 -wi-ao---- 1.97g                                 
 
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  PV        VG        Fmt  Attr PSize PFree
 
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  /dev/vda2  vg_centos2 lvm2 a--  19.51g 4.73g
 
  
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* '''centos3'''
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{|width="100%" border="1" cellpadding="5"
 +
|-
 +
!Option
 +
!Meaning
 +
!Select or query option?
 +
!Example command
 +
|-
 +
| -a
 +
|Select all packages
 +
|select-option
 +
|
 +
|-
 +
| -l
 +
|
 +
|
 +
|
 +
|-
 +
| -i
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|Show the package information.
 +
|
 +
|
 +
|-
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| -f filename
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|
 +
|
 +
|
 +
|-
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|packagename
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|Select just this package
 +
|select-option
 +
|
 +
|}
  
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  This VM has no GUI installed.
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'''Answer the Investigation 1 observations / table contents in your lab log book.'''
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  VG        #PV #LV #SN Attr  VSize VFree
 
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  vg_centos3  2  3  0 wz--n- 16.50g    0
 
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  LV      VG        Attr  LSize 
 
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  lv_home vg_centos3 -wi-ao----  1.00g                                           
 
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  lv_root vg_centos3 -wi-ao----  10.00g                                           
 
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  lv_swap vg_centos3 -wi-ao---- 992.00m                                   
 
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  PV        VG        Fmt  Attr PSize  PFree
 
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  /dev/vda3  vg_centos3 lvm2 a--  14.51g 2.54g
 
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  /dev/vdb  vg_centos3 lvm2 a--  2.00g 2.00g
 
  
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* '''c6host (i.e. "disk pack")'''
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== Investigation 2: How do you install and remove software with RPM? ==
  
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  /dev/sdc3        20G  3.7G  15G  20% /
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# Use the graphical file manager (Nautilus) to change to the directory on your Installation DVD. Go to the sub-directory called '''Packages'''. It should contain a file called: <code>lynx-2.8.6-27.el6.x86_64.rpm</code>
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  /dev/sdc2        29G  4.7G  23G  18% /home
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# Execute the following command: <code>rpm -i lynx-2.8.6-27.el6.x86_64.rpm</code>
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  /dev/sdc1        97G  48G  45G 52% /var/lib/libvirt/images
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# Issue an RPM query to check that lynx is installed. Record this command in your lab log-book.
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# Issue the following command: <code>rpm -e lynx</code>
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# Issue an RPM query to verify that lynx is no longer installed. Record this command in your lab log-book.
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# Issue the following command: <code>rpm -i elinks-0.12.rpm</code>. Did it work? Explain in your lab log-book why this command may not have worked.
  
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= Logical Volume Management (Continued) =
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'''Answer the Investigation 2 observations / questions in your lab log book.'''
  
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{{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'''.}}
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== Investigation 3: How do you install and remove software with ''yum''? ==
  
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== Resources ==
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{{Admon/note|Internet Connection|In order for yum to work you require a connection to the Internet. Establish this connection by using the browser to log into SeneNET}}
  
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Please read this page to get an overview of LVM:
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# Change to your home directory.
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[http://zenit.senecac.on.ca/wiki/index.php/Logical_Volume_Management Logical Volume Management]
 
  
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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.
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<ol>
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<li value="2">Issue the command:  <code>yum install elinks</code> and answer <code>y</code> to the question about installation.
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  <ol type="a">
 +
  <li>Where did ''yum'' get the elinks software?</li>
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  <li>Why could ''yum'' install elinks when rpm couldn't?</li>
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  </ol>
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</li>
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<li>Issue an RPM query to verify that elinks is installed. Record this command in your lab log-book.</li>
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<li>Issue the command: <code>yum remove elinks</code></li>
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<li>Issue an RPM query to verify that elinks is no longer installed. Record this command in your lab log-book.</li>
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<li>Issue this command: <code>yum info cups</code></li>
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</ol>
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::* Based on the result, do you think that cups is a useful package for your system? If not, try removing it.
 +
<ol>
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<li value="8">Unused and unneeded software can present a security risk and ties up disk space needlessly. Find at least 4 other packages (for example: games, sound & video, etc) that you're not using on your system, and remove them. Be careful to ensure that removing those packages does not also remove other software that you do need.</li>
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</ol>
  
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== Investigation 1: How are LVMs are managed using Command-Line Tools  ==
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'''Answer the Investigation 3 observations / questions in your lab log book.'''
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# You are going to repeat the same LVM management operations (as your did with the ''centos2'' VM in '''lab3'''), but you will using command-line tools in the '''centos3''' VM. Since the centos3 VM only operates in command-line mode, you will need to refer to the '''"Logical Volume Management"''' link above.
 
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# Write down the exact commands used at each step, and record appropriate command output:
 
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:: a. Determine the current LVM configuration using the <code>pvs</code>, <code>vgs</code>, and <code>lvs</code> commands.
 
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:: b.Grow the home filesystem to 2G using the command <code>lvextend</code> and <code>resize2fs</code>.
 
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:: 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: [https://wiki.archlinux.org/index.php/fstab https://wiki.archlinux.org/index.php/fstab] ), and then reboot to confirm automatic mount).
 
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:: d.Copy the contents of <code>/etc</code> into <code>/archive</code>.
 
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:: e.Shrink <code>lv_archive</code> to 1G (use <code>umount</code>, <code>resize2fs</code>, <code>lvreduce</code>,  and <code>mount</code>)
 
  
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== Investigation 2: How can a PV be added to an existing VG using Command-Line Tools? ==
 
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# Add an additional 2 GB virtual disk to your ''<u>centos1</u>'' system, we will use it as an additional physical volume.
 
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# Do the rest of this investigation in the command line.
 
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# You should now have both <code>/dev/vda</code> and <code>/dev/vdb</code>.
 
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# Record the size of the volume group and the amount of free space (Hint: use a command that you learned in a previous lab).
 
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# Read the resource [http://tldp.org/HOWTO/Partition/fdisk_partitioning.html Partitioning with fdisk] to learn how to properly create a partition with the fdisk command.
 
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# Use fdisk to partition /dev/vdb with a Linux single partition that fills the whole disk.
 
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# 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.
 
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# Mark ''vdb1'' as a physical volume usable by LVM.
 
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# Add the new physical volume to the existing volume group.
 
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# Verify that the volume group is larger and has more free space.
 
  
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{{Admon/note|Think!|The next part of this investigation requires some research, thought, and creativity.}}
 
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'''Using that additional space, create a separate filesystem for <code>/home</code>:'''
 
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# Create the logical volume <code>lv_home</code> (1G ext4)
 
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# Find a way to move the contents of <code>/home</code> onto it.
 
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# Change your system configuration so that the new filesystem is mounted on <code>/home</code> from now on.
 
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{{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>}}
 
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== Investigation 3: How can I use fdisk to manage storage on my disk pack? ==
 
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'''On your <u>c6host</u> (i.e. "disk pack"), using your choice of the GUI and/or command-line tools:'''
 
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# Create a new partition or logical drive ('''NOT a logical volume!''') - minimum 5G, leaving at least 10G free space in the extended partition.
 
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# Format that partition (i.e. put a filesystem on it).
 
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# Make sure it's mounted automatically on a mountpoint of your choosing (easiest is to create a new directory for a mountpoint).
 
  
 
= User/Group Management =
 
= User/Group Management =

Revision as of 08:21, 28 March 2015


Logical Volume Management (Continued) and User / Group Management

Introduction

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

Prerequisites

Linux Command Online Reference

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

LVM Information Utilities: LVM Management Utilities: Additional Utilities:

Resources on the web

Additional links to tutorials and HOWTOs:


Software Package Management

Investigation 1: How do you query the RPM database?

RPM maintains a database of installed software. This information is very useful to system administrators. In the previous lab you queried that database using RPM with the -q argument. When you query the RPM database, you can separately specify:

  • Do an operational task on one or more packages (like installing or removing a package), using a select-option
  • What information you want about those packages, using a query-option

Perform the following steps:

(Perform investigations 1 - 3 in your host machine (c6host)

  1. Using information from the man page for rpm, fill in this information:
Option Meaning Select or query option? Example command
-a Select all packages select-option
-l
-i Show the package information.
-f filename
packagename Select just this package select-option

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

Investigation 2: How do you install and remove software with RPM?

  1. Use the graphical file manager (Nautilus) to change to the directory on your Installation DVD. Go to the sub-directory called Packages. It should contain a file called: lynx-2.8.6-27.el6.x86_64.rpm
  2. Execute the following command: rpm -i lynx-2.8.6-27.el6.x86_64.rpm
  3. Issue an RPM query to check that lynx is installed. Record this command in your lab log-book.
  4. Issue the following command: rpm -e lynx
  5. Issue an RPM query to verify that lynx is no longer installed. Record this command in your lab log-book.
  6. Issue the following command: rpm -i elinks-0.12.rpm. Did it work? Explain in your lab log-book why this command may not have worked.

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

Investigation 3: How do you install and remove software with yum?

Note.png
Internet Connection
In order for yum to work you require a connection to the Internet. Establish this connection by using the browser to log into SeneNET
  1. Change to your home directory.
  1. Issue the command: yum install elinks and answer y to the question about installation.
    1. Where did yum get the elinks software?
    2. Why could yum install elinks when rpm couldn't?
  2. Issue an RPM query to verify that elinks is installed. Record this command in your lab log-book.
  3. Issue the command: yum remove elinks
  4. Issue an RPM query to verify that elinks is no longer installed. Record this command in your lab log-book.
  5. Issue this command: yum info cups
  • Based on the result, do you think that cups is a useful package for your system? If not, try removing it.
  1. Unused and unneeded software can present a security risk and ties up disk space needlessly. Find at least 4 other packages (for example: games, sound & video, etc) that you're not using on your system, and remove them. Be careful to ensure that removing those packages does not also remove other software that you do need.

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


User/Group Management

Investigation 4: The /etc/passwd file

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

Investigation 5: Adding users

Note.png
Use centos1
Perform these steps in the centos1 system.
  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. 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?
  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.
  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. Be sure to record your observations in your lab notes.
Note.png
Use centos3
Perform these steps in the centos3 virtual machine.
  1. Add your matrix account user to centos3.

Investigation 6: Managing Groups

Note.png
Use centos1
Perform these steps in the centos1 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
    • Which values of GID are reserved for system accounts?
    • Which values of GID are reserved for non-system user accounts?
    • 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

Note.png
Use centos1
Perform these steps in the centos1 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 file. What do you notice?

Be sure to record your observations in your lab notes.

Investigation 8: Modifying users

Note.png
Use centos1
Perform these steps in the centos1 virtual machine.
  1. Read the man page for the usermod command. Note which options change the user's full name, primary group, supplementary groups, and shell.
  1. Add each of your new users to the group ops235 (in other words, add ops235 to each user as a supplementary group).
  2. Examine /etc/group. What has changed?
  3. Use the usermod command to associate each of your pod mates' full name to their user name. With each change, examine their entries in the /etc/passwd file. What has changed?
  4. Be sure to record your observations in your lab notes.

Completing the lab

Important.png
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 centos1 -- you now have two virtual disks on centos1, and therefore two image files, and therefore will need two backup files.

Arrange proof of the following on the screen:

  1. Two PVs on centos1.
  2. Separate /home filesystem (on an LV) in centos1.
  3. Account created on centos3 matching your Matrix account.
  4. List contents of /etc/group file (ops235 group).
  5. List contents of /etc/passwd file (created accounts).
  6. Fresh backup of the virtual machines.

Preparing for the Quizzes

  1. What is a VG? PV? LV?
  2. What is the total size of the "main" VG on your system?
  3. How do you create a LV?
  4. How do you delete an LV?
  5. How would you add the disk partition /dev/sdb7 to your volume group "main"?
  6. How would you increase the size of the root filesystem by 50 MB?
  7. What is the purpose of /etc/fstab?
  8. What is the purpose of /etc/shadow?
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