Difference between revisions of "OPS235 Lab 4 - CentOS6"

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[[Category:OPS235]]
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{{Admon/caution|THIS IS AN OLD VERSION OF THE LAB|'''This is an archived version.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=
 +
 +
==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==
 +
 +
* 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 [http://linuxmanpages.com/ http://linuxmanpages.com]):
 +
 +
{|width="100%" cellpadding="5"
 +
|'''LVM Information Utilities:'''
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|'''LVM Management Utilities:'''
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|'''Additional Utilities:'''
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|- valign="top"
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|
 +
*[http://linuxmanpages.com/man8/vgs.8.php vgs]
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*[http://linuxmanpages.com/man8/lvs.8.php lvs]
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*[http://linuxmanpages.com/man8/pvs.8.php pvs]
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*[http://linuxmanpages.com/man8/vgdisplay.8.php vgdisplay]
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*[http://linuxmanpages.com/man8/lvdisplay.8.php lvdisplay]
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*[http://linuxmanpages.com/man8/pvdisplay.8.php pvdisplay]
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|
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*[http://www.centos.org/docs/5/html/Deployment_Guide-en-US/s1-system-config-lvm.html system-config-lvm] (Tutorial)
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*[http://linuxmanpages.com/man8/lvextend.8.php lvextend]
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*[http://linuxmanpages.com/man8/resize2fs.8.php resize2fs]
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*[http://linuxmanpages.com/man8/lvcreate.8.php lvcreate]
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*[http://linuxmanpages.com/man8/lvreduce.8.php lvreduce]
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*[http://linuxmanpages.com/man8/pvcreate.8.php pvcreate]
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*[http://linuxmanpages.com/man8/vgextend.8.php vgextend]
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|
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*[http://linuxmanpages.com/man8/mount.8.php mount]
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*[http://linuxmanpages.com/man8/umount.8.php umount]
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*[http://linuxmanpages.com/man8/useradd.8.php useradd]
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*[http://linuxmanpages.com/man8/userdel.8.php userdel]
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*[http://linuxmanpages.com/man8/usermod.8.php usermod]
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*[http://linuxmanpages.com/man8/groupadd.8.php groupadd]
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*[http://linuxmanpages.com/man8/groupdel.8.php 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)
 +
:* [http://www.thegeekstuff.com/2011/05/ext2-ext3-ext4/ Linux File Systems (ext2/ext3/ext4)]
 +
:* [http://tldp.org/HOWTO/Partition/fdisk_partitioning.html Partitioning with fdisk]
 +
:* [http://www.linux-tutorial.info/modules.php?name=MContent&pageid=282 Mounting / Unmounting File-systems]
 +
:* [http://www.itwire.com/business-it-news/open-source/14446-uid-and-gid-the-basics-of-linux-user-admin UID and GID explained]
 +
 +
 
= Storage Setup (prior to starting Lab 4) =
 
= 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 />
+
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 />
 
('''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 />
  
Line 43: Line 111:
 
   LV      VG        Attr  LSize   
 
   LV      VG        Attr  LSize   
 
   lv_home vg_centos3 -wi-ao----  1.00g                                             
 
   lv_home vg_centos3 -wi-ao----  1.00g                                             
   lv_root vg_centos3 -wi-ao----  14.54g                                            
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   lv_root vg_centos3 -wi-ao----  10.00g                                            
 
   lv_swap vg_centos3 -wi-ao---- 992.00m                                     
 
   lv_swap vg_centos3 -wi-ao---- 992.00m                                     
 
   
 
   
   PV        VG        Fmt  Attr PSize PFree
+
   PV        VG        Fmt  Attr PSize PFree
   /dev/vda3  vg_centos3 lvm2 a--  14.51g   0
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   /dev/vda3  vg_centos3 lvm2 a--  14.51g 2.54g
   /dev/vdb  vg_centos3 lvm2 a--  2.00g   0
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   /dev/vdb  vg_centos3 lvm2 a--  2.00g 2.00g
  
 
* '''c6host (i.e. "disk pack")'''
 
* '''c6host (i.e. "disk pack")'''
Line 63: Line 131:
  
 
Please read this page to get an overview of LVM:
 
Please read this page to get an overview of LVM:
 +
[http://zenit.senecac.on.ca/wiki/index.php/Logical_Volume_Management 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  ==
 
== 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 ''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.
 
# 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.
 
# Write down the exact commands used at each step, and record appropriate command output:
 
# 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.
+
:: a. Determine the current LVM configuration using the <code>pvs</code>, <code>vgs</code>, and <code>lvs</code> commands.
## Grow the home filesystem to 2G using the command <code>lvextend</code> and <code>resize2fs</code>.
+
:: b.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).
+
:: 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).
## Copy the contents of <code>/etc</code> into <code>/archive</code>.
+
:: d.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>)
+
:: 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 VG using Command-Line Tools? ==
 
== Investigation 2: How can a PV be added to an existing VG using Command-Line Tools? ==
Line 80: Line 149:
 
# You should now have both <code>/dev/vda</code> and <code>/dev/vdb</code>.
 
# 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).
 
# Record the size of the volume group and the amount of free space (Hint: use a command that you learned in a previous lab).
# Use fdisk to partition /dev/vdb with a single partition that fills the whole disk.
+
# 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.
 +
# 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.
 
# 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.
 
# Mark ''vdb1'' as a physical volume usable by LVM.
 
# Mark ''vdb1'' as a physical volume usable by LVM.
Line 94: Line 164:
 
{{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>}}
 
{{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? ==
+
== Investigation 3: How can I use fdisk to manage storage on my disk pack? ==
'''On your <u>f17host</u> (i.e. "disk pack"), using your choice of the GUI and/or command-line tools:'''
+
'''On your <u>c6host</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.
+
# Create a new partition or logical drive ('''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).
+
# Format that partition (i.e. put a filesystem on it).
# Grow the root filesystem to fill the available space.
+
# 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 =
Line 117: Line 185:
 
== Investigation 5: Adding users ==
 
== Investigation 5: Adding users ==
  
{{Admon/note|Use f17host|Perform these steps in the '''f17host''' 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).}}
+
{{Admon/note|Use centos1|Perform these steps in the '''centos1''' system.}}
  
 
# Read the man page for the useradd command.
 
# Read the man page for the useradd command.
Line 140: Line 208:
 
# Be sure to record your observations in your lab notes.
 
# Be sure to record your observations in your lab notes.
  
{{Admon/note|Use fedora3|Perform these steps in the '''fedora3''' virtual machine.}}
+
{{Admon/note|Use centos3|Perform these steps in the '''centos3''' virtual machine.}}
# Add your matrix account user to '''fedora3'''.
+
# Add your matrix account user to '''centos3'''.
  
 
== Investigation 6: Managing Groups ==
 
== Investigation 6: Managing Groups ==
  
{{Admon/note|Use fedora1|Perform these steps in the '''fedora1''' virtual machine.}}
+
{{Admon/note|Use centos1|Perform these steps in the '''centos1''' virtual machine.}}
  
 
# Read the man page for the groupadd and groupdel commands.
 
# Read the man page for the groupadd and groupdel commands.
Line 152: Line 220:
 
#* Which values of GID are reserved for system accounts?
 
#* Which values of GID are reserved for system accounts?
 
#* Which values of GID are reserved for non-system user 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 lowest available GID number for non-system users?
 
#* What is the default group name of a new user?
 
#* What is the default group name of a new user?
 
#* Add a new group named ops235 with a GID of 600.
 
#* Add a new group named ops235 with a GID of 600.
Line 166: Line 234:
 
== Investigation 7: Deleting users ==
 
== Investigation 7: Deleting users ==
  
{{Admon/note|Use fedora1|Perform these steps in the '''fedora1''' virtual machine.}}
+
{{Admon/note|Use centos1|Perform these steps in the '''centos1''' virtual machine.}}
  
 
# Read the man page for the userdel command. Note which option automatically removes the users home directory when that user is deleted.
 
# Read the man page for the userdel command. Note which option automatically removes the users home directory when that user is deleted.
Line 179: Line 247:
 
== Investigation 8: Modifying users ==
 
== Investigation 8: Modifying users ==
  
{{Admon/note|Use fedora1|Perform these steps in the '''fedora1''' virtual machine.}}
+
{{Admon/note|Use centos1|Perform these steps in the '''centos1''' 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.
 
# Read the man page for the usermod command. Note which options change the user's full name, primary group, supplementary groups, and shell.
Line 185: Line 253:
 
# Add each of your new users to the group ops235 (in other words, add ops235 to each user as a supplementary group).
 
# 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?
 
# 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?
+
# 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 <code>/etc/passwd</code> file. What has changed?
 
# Be sure to record your observations in your lab notes.
 
# 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 =
 
= 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.}}
+
{{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 ''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:
 
Arrange proof of the following on the screen:
# Two PVs on '''fedora1'''.
+
# Two PVs on '''centos1'''.
# Separate <code>/home</code> filesystem (on an LV) in '''fedora1'''.
+
# Separate <code>/home</code> filesystem (on an LV) in '''centos1'''.
<!-- # Unnecessary accounts and groups have been removed on '''fedora1'''. -->
+
# Account created on '''centos3''' matching your Matrix account.
# Account created on '''fedora3''' matching your Matrix account.
 
 
# List contents of '''/etc/group''' file (ops235 group).
 
# List contents of '''/etc/group''' file (ops235 group).
 
# List contents of '''/etc/passwd''' file (created accounts).
 
# List contents of '''/etc/passwd''' file (created accounts).

Latest revision as of 12:31, 24 September 2018

Stop (medium size).png
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

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:


Storage Setup (prior to starting Lab 4)

At this point, having completed Lab 3 you should have roughly the following disk storage setup:
(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)

  • centos1
 This VM has a GUI and no free space in the VG.

 VG         #PV #LV #SN Attr   VSize VFree
 vg_centos1   1   2   0 wz--n- 9.80G    0

 LV      VG         Attr   LSize  
 lv_root vg_centos1 -wi-ao   8.83G                                     
 lv_swap vg_centos1 -wi-ao 992.00M                                     

 PV         VG         Fmt  Attr PSize PFree
 /dev/vda2  vg_centos1 lvm2 a-   9.80G    0
  • centos2
 This VM has a GUI and free space in the VG.

 VG         #PV #LV #SN Attr   VSize VFree
 vg_centos2   1   4   0 wz--n- 19.51g 4.73g

 LV      VG         Attr   LSize   
 lv_archive vg_centos2 -wi-ao---- 1.00g                                            
 lv_home    vg_centos2 -wi-ao---- 4.00g                                            
 lv_root    vg_centos2 -wi-ao---- 7.81g                                            
 lv_swap    vg_centos2 -wi-ao---- 1.97g                                  

 PV         VG         Fmt  Attr PSize PFree
 /dev/vda2  vg_centos2 lvm2 a--  19.51g 4.73g
  • centos3
 This VM has no GUI installed.

 VG         #PV #LV #SN Attr   VSize VFree
 vg_centos3   2   3   0 wz--n- 16.50g    0 

 LV      VG         Attr   LSize  
 lv_home vg_centos3 -wi-ao----   1.00g                                            
 lv_root vg_centos3 -wi-ao----  10.00g                                            
 lv_swap vg_centos3 -wi-ao---- 992.00m                                    

 PV         VG         Fmt  Attr PSize  PFree
 /dev/vda3  vg_centos3 lvm2 a--  14.51g 2.54g
 /dev/vdb   vg_centos3 lvm2 a--   2.00g 2.00g
  • c6host (i.e. "disk pack")
 /dev/sdc3        20G  3.7G   15G  20% /
 /dev/sdc2        29G  4.7G   23G  18% /home
 /dev/sdc1        97G   48G   45G  52% /var/lib/libvirt/images

Logical Volume Management (Continued)

Note.png
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: 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

  1. 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.
  2. Write down the exact commands used at each step, and record appropriate command output:
a. Determine the current LVM configuration using the pvs, vgs, and lvs commands.
b.Grow the home filesystem to 2G using the command lvextend and resize2fs.
c.Create a new 2G LV containing an ext4 filesystem and mount it at /archive (use mkdir, lvcreate, mkfs, mount, edit the file /etc/fstab (read the resource: https://wiki.archlinux.org/index.php/fstab ), and then reboot to confirm automatic mount).
d.Copy the contents of /etc into /archive.
e.Shrink lv_archive to 1G (use umount, resize2fs, lvreduce, and mount)

Investigation 2: How can a PV be added to an existing VG using Command-Line Tools?

  1. Add an additional 2 GB virtual disk to your centos1 system, we will use it as an additional physical volume.
  2. Do the rest of this investigation in the command line.
  3. You should now have both /dev/vda and /dev/vdb.
  4. Record the size of the volume group and the amount of free space (Hint: use a command that you learned in a previous lab).
  5. Read the resource Partitioning with fdisk to learn how to properly create a partition with the fdisk command.
  6. Use fdisk to partition /dev/vdb with a Linux single partition that fills the whole disk.
  7. Check the messages printed when fdisk exits -- you may need to reboot the system in order for the new partition table to take effect.
  8. Mark vdb1 as a physical volume usable by LVM.
  9. Add the new physical volume to the existing volume group.
  10. Verify that the volume group is larger and has more free space.
Note.png
Think!
The next part of this investigation requires some research, thought, and creativity.

Using that additional space, create a separate filesystem for /home:

  1. Create the logical volume lv_home (1G ext4)
  2. Find a way to move the contents of /home onto it.
  3. Change your system configuration so that the new filesystem is mounted on /home from now on.
Idea.png
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: restorecon -r /home

Investigation 3: How can I use fdisk to manage storage on my disk pack?

On your c6host (i.e. "disk pack"), using your choice of the GUI and/or command-line tools:

  1. Create a new partition or logical drive (NOT a logical volume!) - minimum 5G, leaving at least 10G free space in the extended partition.
  2. Format that partition (i.e. put a filesystem on it).
  3. 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

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?