The purpose of this lab is to demonstrate how a Linux system administrator can monitor hard disk space availability, and to manage file system size via the Logical Volume Manager (LVM) application. This lab will also demonstrate how to manually mount (i.e. connect) and unmount (disconnect) partitions to file system directories, and demonstrate how to have partitions automatically mounted to directories upon Linux system startup. <u>Main Objectives<br/u> :* Using '''LVM''' to '''resize partitions graphically and via command-line'''.:* Create, partition and format '''virtual hard disks''' to increase the size of a file system.:* Connecting Manually connect and Disconnecting Directories disconnect directories (mount points) to existing partitions ('''mount''', '''umount''').

:* Using '''LVM''' to '''resize partitions graphically and via commands'''.:* Create, partition and format '''virtual hard disks''' to increase the size of a file system.:* Create a Bash Shell Script script to '''monitor and report low disk size''' (run periodically in '''crontab''').

|width="10%" |<u>User ManagementLVM Information:</u>*[http://unixhelpman7.org/linux/man-pages/man8/vgs.ed8.achtml vgs]<br>*[http://man7.ukorg/CGIlinux/man-cgi?useradd+pages/man8/pvs.8 useradd.html pvs]<br>*[http://unixhelp.ed.acman7.ukorg/CGIlinux/man-cgi?userdel+pages/man8/lvs.8 userdel.html lvs]<br>*[http://unixhelp.ed.acman7.ukorg/CGIlinux/man-cgi?usermod+pages/man8/vgdisplay.8 usermod.html vgdisplay]<br>*[http://unixhelp.ed.acman7.ukorg/CGIlinux/man-cgi?groupadd+pages/man8/pvdisplay.8 groupadd.html pvdisplay]<br>*[http://unixhelp.ed.acman7.ukorg/CGIlinux/man-cgi?groupdel+pages/man8/lvdisplay.8 groupdel.html lvdisplay]<br>|width="10%" |<u>Managing ServicesLVM Management</u>*[http://unixhelpwww.centos.edorg/docs/5/html/Deployment_Guide-en-US/s1-system-config-lvm.achtml system-config-lvm]<br>*[http://man7.ukorg/CGIlinux/man-cgi?chkconfig+pages/man8/lvextend.8 chkconfig.html lvextend]<br>*[http://unixhelpman7.edorg/linux/man-pages/man8/lvcreate.ac8.ukhtml lvcreate]<br>*[http:/CGI/man7.org/linux/man-cgi?service+pages/man8/lvreduce.8 service.html lvreduce]<br>*[http://wwwman7.dsmorg/linux/man-pages/man8/pvcreate.fordham8.eduhtml pvcreate]<br>*[http://cgi-binman7.org/linux/man-cgipages/man8/vgextend.pl?topic=systemctl systemctl8.html vgextend]<br>

*[http://man7.org/linux/man-pages/man5man8/passwdmount.58.html /etc/passwdmount]<br>*[http://man7.org/linux/man-pages/man5man8/groupumount.58.html /etc/groupumount]<br>*[http://man7.org/linux/man-pages/man5man1/shadowdf.51.html /etc/shadowdf]<br>*[http://archive.linuxfromscratchman7.org/blfslinux/man-museumpages/man1/du.1.0html du]<br>*[http://www.lehman.cuny.edu/cgi-bin/BLFSman-cgi?awk+1awk]<br>*[http://tldp.0org/HOWTO/postlfsPartition/skelfdisk_partitioning.html /etc/skelfdisk]<br>*[http://www.cyberciti.biz/faq/howto-format-create-linux-filesystem/ mkfs]*[http://zenitman7.senecacorg/linux/man-pages/man5/fstab.on5.cahtml /etc/fstab]*[http:/wiki/indexcode.phptutsplus.com/Init_vs_systemd init vs systemdtutorials/scheduling-tasks-with-cron-jobs--net-8800 Using crontab] 

= INVESTIGATION 1: User'''LVM''' ('''Logical Volume Management''') is used to manage hard disk drives /Group Management =partitions for Linux and Unix systems. LVM provides more flexibility than just partitioning hard disks. '''Volume Groups''' are areas used to define '''Physical Volumes''' (i.e. hard disks, disk partitions, or other forms of storage devices). '''Logical Volumes''' are then used to relate directories (mount points) to a specific physical volume or for a "range" or "span" of physical volumes.

User account management is a very important operation that a LVM allows more flexibility and growth potential for Linux sysadmin does on a consistent basissystems (for example, having Logical volumes span multiple hard disks). The sysadmin not only needs to add or remove user accounts CentOS uses LVM by issuing commands, but default upon installation. Other Linux distributions may need to automate user account creations a large number (batch) of potential employees. There are many features with provide the Linux command capacity to create new users including: specification of a home directoryinstall LVM, type of shell used, name, password and time-limit (referred to as "aging") for a new user account. Remove user accounts also have options such as removing the user account but keeping the home directory for reference or evidence of "wrong-doing"

=== Part 1: Manage LVM Graphically=== [[Image:lvm1.png|thumb|500px|right|The '''system-config-lvm''' application allows the Linux system administrator to manage LVMs Graphically. Your LVM information for '''centos2''' VM should be similarly displayed.]]# Let's learn to administer (manage) our LVM graphically for our '''centos2''' Virtual Machine.# Launch your '''centos2''' VM and open a shell terminal.# CentOS provides a tool called '''system-config-lvm''' to graphically administer LVM.<br><br>'''NOTE:''' This tool may be replaced by a future graphical LVM management tool and is NOT currently available in the default repositories. We will now perform a "work-around" in order to make the system-config-lvm utility work in our system.<br><br># Issue the following command to download the system-config-lvm rpm:<br><b><code><span style="color:#3366CC;font-size:1.2em;">wget https://kojipkgs.fedoraproject.org//packages/system-config-lvm/1.1.18/1.fc19/noarch/system-config-lvm-1.1.18-1.fc19.noarch.rpm</span></etccode></passwd b><br>(Although it is an rpm file for the Fedora Distribution, it will also work for Centos7).<br><br># Make certain that you are logged in as '''root'''.# Try issuing the command: <b><code><span style="color:#3366CC;font-size:1.2em;">rpm -i ./system-config-lvm-1.1.18-1.fc19.noarch.rpm</span></code></b><br>You should notice an error.# Use the '''yum install''' command to resolve the following dependencies:<ul><li><b><code><span style="color:#3366CC;font-size:1.2em;">yum install gnome-python2-bonobo</span></code></b></li><li><b><code><span style="color:#3366CC;font-size:1.2em;">yum install gnome-python2-gnome</span></code></b></li><li><b><code><span style="color:#3366CC;font-size:1.2em;">yum install usermode-gtk</span></code></b></li></ul><br><ol> <li value="8">Re-issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">rpm -i ./system-config-lvm-1.1.18-1.fc19.noarch.rpm</span></code></b><br>It should work this time.</li><li>Run the command: <b><code><span style="color:#3366CC;font-size:1.2em;">system-config-lvm</span></code></b></li><li>On the left-hand side, you can click on the '''Volume Group''', '''Physical Volume''' and '''Logical Volumes''' and view their properties on the on the right-hand side.</li><li>Determine the current LVM configuration by clicking on the appropriate element and reading the properties in the right-hand panel -- write down the answers: <ol type="a"> <li>What are the names and sizes of the '''Volume Group'''?</li> <li>What is the name and size of the '''Physical Volumes'''?</li> <li>What are the names and sizes of the '''Logical Volumes'''?</li> <li>Is there any space in the VG which is not allocated to a LV?<br><br></li> </ol> </li> <li>Click on '''Logical View''' (i.e. above home, root, swap) and then click '''Create New Logical Volume''' button. What happens? Why do you think this happened?<br><br>We will now create another partition ('''/dev/vda3''') using the '''fdisk''' utility, format this newly-created partition so we can create another logical volume called '''archive'''.<br><br> </li> <li>Quit the '''system-config-lvm''' application.</li> <li>In the terminal as root, issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">ls /dev/vd*</span></code></b><br><br>'''NOTE:''' If nothing displays, issue the command: '''ls /dev/sd*''' and use that device pathname '''/dev/sda''' instead.<br><br> <li>Issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">fdisk /dev/vda</span></code></b><br>(or ''fdisk /dev/sda'' if the previous command didn't work)</li> <li>At the fdisk prompt issue the command: '''p'''. What does this do?</li> <li>Now issue the commands '''n''' (new partition), '''p''' (primary partition), '''3''' (i.e. next available partition number). When prompted for initial block, '''press enter to accept the default beginning block size''', and '''type: +2G''' at ending block (create 2GB for partition) and '''press enter'''. </li> <li>At the fdisk prompt, issue the command '''p''' to review the partition information, then type '''w''' to save partition table and exit (ignore WARNING message).</li> <li>You <u>'''must'''</u> restart your centos2 VM to allow changes to take effect</li> <li>Open a terminal as root, and format your newly-created partition by issuing the command: <b><code><span style="color:#3366CC;font-size:1.2em;">mkfs -t ext4 /dev/vda3</span></code></b><br>(or ''mkfs -t ext4 /dev/sda3'')</li></ol>{| width="40%" align="right" cellpadding="10"|- valign="top"|[[Image:lvm3.png|thumb|right|500px|What '''system-config-lvm''' display should appear after using '''fdisk''' to create new partition (/dev/sda3), '''formatting''' partition, '''adding partition to LVM''', and '''allocating partition''' to our default volume group.]]|[[Image:lvm4.png|thumb|right|200px|Creating a new logical volume from our newly created physical volume]]|}<ol> <li value="21">'''Restart the system-config-lvm utility'''. Do you see a new /dev/sda3 partition under Physical Volumes?</li> <li>To add the newly created partition, you need to add it into LVM to be used. '''Exit the system-config-lvm utility''' and '''issue the following command to add the partition into LVM:'''<br><b><code><span style="color:#3366CC;font-size:1.2em;">pvcreate /dev/vda3</span></code></b> (or ''pvcreate /dev/sda3'' ) (enter '''y''' to proceed - ignore warning)</li> <li>'''Restart system-config-lvm'''. You should notice a section at the bottom indicating <u>Unallocated</u> Physical Volumes. Click on the <u>unallocated</u> partition /dev/vda3 and then click '''Add to Existing Volume Group''' (click on other button in next screen to continue). The screen should now show the partition ''/dev/vda3'' contained in our default Volume Group (refer to diagram on right-side for reference).</li> <li>Click on Logical View (i.e. above home, root, swap), and then click on '''Create New Logical Volume''' button and fill out the details for this new logical volume including: size: '''1GB''', LV Properties: '''linear''', file system: '''ext4''' file system name: '''archive''', select '''mount''' and mount it at: '''/archive'''. Have the system create the directory ''/archive'' if it does not exist (Refer to diagram on right for reference).</li> <li>Confirm that this new Logical Volume now exists by changing to the directory /archive. Did you need to restart your centos2 VM to confirm that the '''/archive''' directory is now on your '''centos2''' VM?</li> <li>Use system-config-lvm to resize (i.e. edit) the '''archive''' logical volume to '''1.5 GB''' and verify your results.</li></ol> 

# Look at the <b><code><span style="color:#3366CC;font-size:'''Answer Part 1.2em;">/etc/passwd</span></code></b> file.# Make note of the contents of that file.# Read about the file: http://man7.orgobservations /linux/man-pages/man5/passwd.5.html # 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 accountsquestions in your lab log book. What is the pattern?'''

===Part 2: Managing LVM Via Command Line & Adding Virtual Hard Drives===[[Image:add_virtual_disk.png|thumb|400px|right|You can add virtual hard disks for a VM by changing to the '''Details'''Answer section for the Part 1 observations / questions VM (as opposed to ''console''), click '''Add Hardware''', fill information in the '''Add New Virtual Hardware''' dialog box and clicking '''Finish'''.]]Let's say that you have run out of disk space on your lab log book.'''centos3''' VM, and you need more space on the root file-system in order to host more web-pages, or to support a larger database. What are your options? Getting a replacement hard-drive would probably require re-installation of the operating system and/or backing up and restoring data on the old hard disk.

# Perform this Part in your '''centos3''' VM.# Run the following commands and make note of the output:::<b><code><span style="color:#3366CC;font-size:1.2em;">ls /dev/vd*</span></code></b>::<b><code><span style="color:#3366CC;font-size:1.2em;">pvs</span></code></b>::<b><code><span style="color:#3366CC;font-size:1.2em;">vgs</span></code></b>::<b><code><span style="color:#3366CC;font-size:1.2em;">lvs</span></code></b>::<b><code><span style="color:#3366CC;font-size:1.2em;">df -h</span></code></b><ol> <li value="3">Record the size of the volume group and the amount of free space</li> <li>At the top of your VM window (make certain <u>not</u> full screen mode) click the '''view''' menu and change view from '''Console''' to <u>Details</u>''' .</li> <li>At the bottom left-hand corner, click '''Add Hardware''' and add a new storage device of '''2GBs''', make sure the '''Bus type''' is selected as: '''VirtIO disk'''.<br><br>'''NOTE: Make certain to click "select managed or other existing storage", and fill in the pathname circled in red as shown in the diagram on the right-hand-side.<br><br>'''Answer </li> <li>Go back to the '''console''' view</li> <li>Issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">ls /dev/vd*</span></code></b>, what has changed?</li> <li>Use '''fdisk''' (''refer to how to use in Part 2 observations 1'') to create a new single primary partition for '''/ questions in dev/vdb''' that fills the entire disk, save partition table (accepting defaults prompts would work), restart your lab log book'''centos3''' VM and then '''format''' that partition for file type: '''ext4'''.</li> <li>Now we'll make the new device a '''physical volume''', add it to the '''volume group''', and extend '''lv_root''':</li></ol>:: <b><code><span style="color:#3366CC;font-size:1.2em;">pvcreate /dev/vdb1</span></code></b> (enter '''y'''to proceed - ignore warning)

:: <b><code><span style== Part 3"color:#3366CC;font-size:1.2em;">vgs</span></code></b> (to determine: Managing Groups ==''name_of_volumegroup'')

#Remain in your '''centos1''' VM for this section.# Read the man page for the <b><code><span style="color:#3366CC;font-size:1.2em;">groupadd</span></code></b> and <b><code><span style="color:#3366CC;font-size:1.2em;">groupdel</span></code></b> commands.# Note which option allows you to set the Group ID number (vgextend ''name_of_volumegroup'GID''') when you create a new group.# Examine the file <b><code><span style="color:#3366CC;font-size:1.2em;">/etc/group</span></code></b>#* 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 <b><code><span style="color:#3366CC;font-size:1.2em;">ops235< /span><dev/code></b> with a GID of <b><code><span style="color:#3366CC;font-size:1.2em;">600vdb1</span></code></b>.#* The management at your organization have concerns regarding some irresponsible users on your system.#** Add a new group named '''investigation'''.#** Look at '''/etc/group''' and note the GID of group called '''investigation'''.#** What GID is given to a new group if you do not specify it?#** In the file, add those users to the end of the concerned group (separate each user-name with a comma).#** Those individuals have explained their actions to management and the crisis has been resolved. Delete the '''investigation''' group.#** Look at '''/etc/group''' again and note the change.

:: <b><code><span style="color:#3366CC;font-size:1.2em;">lvextend -L +2G -r ''name_of_volumegroup''Answer the Part 3 observations / questions in your lab log book.'''lv_root</span></code></b>

{| width="40%" align= Part 4"right" cellpadding="10"|- valign="top"|{{Admon/note|LVM Safeguards When Reducing File System Size|In older versions of LVM, the system administrator had to be careful when reducing the size of Linux file-systems using LVM. This usually required to separate operations: Deleting <ul><li>Reducing the file-system to make room (''resize2fs'')</li><li>Reduce the logical volume by using the '''lvreduce''' command</li></ul>This used to be performed to prevent a catastrophic loss of data if the logical volume was resize smaller than the available space on the file-system.<br>The newer LVM commands have "safeguards" (eg. option '''-r''' to prevent destroying the file-system (thus making the ''resize2fs'' command <u>obsolete</ Modifying Users ==u>). '''|}}|}

#Remain in your <ol> <li value="13">Now rerun the '''ls /dev/vd*''' , '''pvs'''centos1, ''' VM for this section.# Read the man page for the vgs'''userdel, ''' command. Note which option automatically removes the users home directory when that user is deleted.# Delete the user lvs'''ops235_1and ''' using the command <b><code><span style="color:#3366CC;fontdf -size:1h''' commands.2em;">userdel ops235_1</spanli> </code></bli># Delete Record the user '''ops235'''_2 using the same command with the option which removes the home directory size of the user.# Check volume group and the contents amount of the /home directoryfree space. What do you noticehas changed and what caused those changes?# Check the contents of the <b/li> <codeli><span style="color:#3366CC;fontAmong the changes, note that your root file-size:1.2em;">/etc/groupsystem is now 2GB bigger, and you have not even rebooted your machine since you used fdisk to create a partition!</span></codeli> </bli> file. What do you notice?# Read Reduce the man page for the usermod command. Note which options change size of the user's full name, primary group, supplementary groups, and shell.# Create a new user account called ''lv_root'noobie''partition by ' for the employee: '''"Really Green"1GB''' . Assign a password for that newly created user.# Management has indicated that this employee be on on probation for 3 months. Use by issuing the '''usermod''' following command to set the account for noobie to expire in 3 months from this day as part of the security policy of this organization.# Add each of your new users to the group ops235 (in other words, add ops235 to each user as a supplementary group).# Examine :<br><b><code><span style="color:#3366CC;font-size:1.2em;">lvreduce ''name_of_volumegroup''/etc/grouplv_root --size -1G</span></code></b></li>Confirm that the file system has been reduced. What has changed?# Use </li><li>Increase the '''usermod''' command to change the full name size of the user account '''noobie''lv_root' from ''partition by another '"Really Green"''1GB' to '''"Outstanding Employee"'''. Examine by issuing the result of running that command in the :<br><b><code><span style="color:#3366CC;font-size:1.2em;">lvextend ''name_of_volumegroup''/etc/passwdlv_root --size +1G</span></code></b> </li>Confirm that the filesystem can been increased. What has changed?# Use </li><li>Record the '''usermod''' command to extend the use of their account for 5 years as of today.# Be sure to record your observations LVM Management commands in your lab noteslog-book.</li></ol>

=INVESTIGATION '''Answer Part 2: Managing System Services and Run-levels=observations / questions in your lab log book.'''

The process may not be hard, but knowing how to stop, start, restart and check the status of services is absolutely critical to a Linux server. '''Aside from learning to trouble= INVESTIGATION 2: ADDITIONAL FILE-shoot problems''' by checking the status of running services, '''understanding how to manage services is critical to help protect a Linux server from penetration''' (this term is referred to as "'''Hardening a system'''"). Sometimes it is "what we don't know" that can harm us. One key element in hardening a computer system is to disable non essential networkng services to allow IDSs ('''Intrusion Detection Systems''') to focus on a narrower range of policy violations. A Debian-based penetration testing distribution called Kali (formerly referred to as '''BackTrax''') allows sysadmins and security professionals to identify vulnerabilities in their computer systems, and thus improve (harden) their systems against penetration. Learning to monitor the status, enable and disable networking services underlies the '''Backtrax''' motto:<br><br>'''''"The quieter you are, then more you will hear..."'''''<br><br>SYSTEM OPERATIONS =

=== Part 1: How We take for granted that a file-system must be mounted (for example the root partition) in order for a Linux system to be usable upon system start-up. This was create automatically for the '''/archive''' mount point automatically when we used the system-config-lvm utility in the previous investigation. We need to learn now to do we Manage System Services? ===this manually by editing or adding an entry in the ''/etc/fstab'' file. The '''/etc/fstab''' (file system table) contains entries to mount various file systems automatically upon start-up of the Linux system.

We have seen that maintaining unneeded The Linux system administrator also has the ability to manually '''mount''' (connect) and '''packages can be a security riskun-mount''' due (disconnect) partitions in order to perform maintenance on the unnecessary increase in file system (for example un-mounting the complexity of your system. Similarly, it is also unnecessarily hazardous, and even more so, to leave unneeded services running. In this investigation, we will learn how to '''control services, and turn off those services that we think are not necessary to help reduce security risks/home'''partition to install software and prevent users from logging in during that process).}}

== Part 1: Mounting and Un-mounting Partitions ==[[Image:mount.png|thumb|700px|right|Using the '''mount''' command with no arguments displays file-systems that are already mounted. The Linux system administrator can use the '''mount''' and '''umount''' commands to connect and disconnect different partitions from the file-system to perform maintenance.]]# Perform this part in your '''centos2'''Answer VM.# As you may recall in Part 1 observations of Investigation 1, we created another logical volume called '''archive''' using the graphical application '''system-config-lvm'''. This logical volume should be mounted (connected) to our existing file-system (2GB).# Issue the following command: <b><code><span style="color:#3366CC;font-size:1.2em;">mount</span></code></b># What is the purposed of issuing this command without arguments? Can you see the '''/archive''' mount point?# Confirm that the directory named '''/ questions archive''' is mounted.# You can use the '''umount''' command to unmount a file-system (eg. for maintenance purposes). Note the the name of the command is umount, <u>not</u> unmount.# Make certain you are not located in the /archive directory, and issue the following command to unmount the /archive directory:<br><b><code><span style="color:#3366CC;font-size:1.2em;">umount /archive</span></code></b># Issue the '''mount''' command (without arguments) to confirm it has been unmounted.# View the contents of the file-system table /etc/fstab by issuing the following command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">cat /etc/fstab</span></code></b># Note the line that automatically mounts a file-system (''/dev/sda3'', type ''ext4'') to '''/archive'''. This was automatically performed for you via the '''system-config-lvm''' utility.# View and record the fields for the '''/archive''' mount in your lab log booklogbook, and then issue the following command to reconnect or mount '''/archive''':<br><b><code><span style="color:#3366CC;font-size:1.2em;">mount &nbsp; -t ext4 &nbsp; /dev/centos_centos2/archive &nbsp; /archive</span></code></b><br><br>'''NOTE:''' If you are having problem mounting, use the /dev pathname listing in your /etc/fstab file.<br><br># Confirm that this file-system has been properly mounted. Note: You could have also issued the command: '''mount -a''' to <u>automatically</u> mount the file-systems contained in the '''/etc/fstab''' file.<br><br>Tip: If you had to do manually configure /etc/fstab (eg. only in text-based mode - centos3), you could have issued the command (as root):<br> <b><code><span style="color:#3366CC;font-size:1.2em;">echo "/dev/centos_centos2/archive /archive ext4 defaults 1 2" >> /etc/fstab</span></code></b><br>(although we don't need to do this, since it was already done).<br><br># '''A curious question''': If root needs to unmount the '''/home''' directory for maintenance but we had to first login in graphically as a regular user, then su to "root", isn't our regular user still logged in so we can't un-mount the /home directory?!? How can we as a Linux System Administrator get around the problem (hint: you already learned it somewhere in lab3!!! Wow, using what we already taught can pay-off in the future ... lol!).

Running servers '''Answer the Part 1 observations / questions in graphical mode will make your system most likely to be penetrated. The X-windows framework can be vulnerable to attacks when these servers are connected to the Internet. This is why when you install server versions of Linux, they work in text-based mode only. Desktop versions of Linux are then installed on workstations (working in graphical mode) that connect to the server (for security reasons)lab log book.'''

#Perform this part Remain in both your '''centos2''' and '''centos3''' VMsVM for this section.<ol> <li value="2"># Issue the following Linux command: <ul> <li><b><code><span style="color:#3366CC;font-size:1.2em;">runleveldf -h</span></code></b></li> </ul> </li> <li># Note the difference in output between disk space usage for '''centos2/''' and , '''centos3/home'''.</li> <li>You can use the , and '''init/archive''' command to change the current run-levelpartitions. See # If a list partition is running out of runlevels [https://www.centos.org/docs/5/html/5.2/Installation_Guide/s2-init-boot-shutdown-rl.html here].</li><li> Use available space, the '''man''' command to learn how to use Linux System Administrator can reallocate space among partitions or add another disk and grow the '''init''' commandfile system (like you did in a previous investigation). Use this command to change The administrator also can investigate the current run-level in '''centos2''' cause of low disk space. Two examples immediately come to '''3'''mind: excessive use of space from users, and potential penetration from hackers. What happened?</li> <li>Issue # To investigate excessive disk usage by regular users, you can obtain a total amount of disk usage for that user by issuing the following Linux command: <ul> <libr><b><code><span style="color:#3366CC;font-size:1.2em;">startxdu -hs /home/regularuserid</span></code></b># To provided a more detailed list of usage (file-by-file), issue the command:</libr> </ulb> </licode> <lispan style="color:#3366CC;font-size:1.2em;">What happens?du -h /home/regularuserid | more</lispan> <li/code>Log-off your graphical system. You should return to your shell prompt.</lib> <li>Using systemd requires # If there is a different recurring space usage problem with regular users, the Linux system administrator can impose quotas (caps on disk usage). This method of setting text mode is not taught in this course.# The methods to monitor potential penetration to a Linux system are too numerous, and graphical modeare taught in other coures (for example: SEC520). You can refer On method of monitoring potential penetration is to this link look for future referenceabnormally large files. Issue the command: [http<br><b><code><span style="color:#3366CC;font-size://fedoraproject1.org2em;">find -P /wiki/Systemd#How_do_I_change_the_runlevel.3F How to Change Run-Levels with Systemd]size +100000k</lispan><li/code>Restart your centos2 machine, and make certain that it runs in '''graphical''' mode</lib> </li>Why would # Did you want see any files that are that size?# The next section will apply some of these tools we have discussed into a shell script and crontab entry to make periodically monitor and contact the system administrator of potential disk space issues (before they become a graphical Linux system run in text-based mode?</li></ol>serious problem).

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

==Automating Routine Tasks (Scheduling The Running of Shell ScriptingScript Via Crontab)==

|{{Admon/tip|Bash Shell Scripting Tips:|<br><ul><li>'''The case statementUsing awk to Manipulate Text:'''<br><br>The case statement is a control-flow statement Legend has it that works in a similar way as the if-elif-else statement (but is more concise). This statement presents scenerios or "cases" based on values or regular expressions (not ranges of values like if-elif-else statements). After action(s) are taken for a particular scenerio (or "case"), a break statement (''';;awk''') is used command was invented by three C programmers that wanted to "break-out" of create a utility in Unix that had programming syntax more like C programming. People started to use the statement (command and found it very useful for report generation and not perform other actions). A default case (*) is also used to catch exceptionsfile repair or manipulation.<br><br><u>The command mimics a C program, with braces '''Examples (try in shell script):{ }'''</u><br><br>''read -p "pick that surround the action to perform based on records from a door (1 or 2): " pick<br>case database file matching either test conditions, regular expressions, etc. Fields appear as numbers with $pick in.<br>&nbsp; 1) echo "You win a car!" ;;<br>&nbsp; 2) echo "You win a bag of dirt!" ;;<br>&nbsp; *) echo "Not a valid entry"<br>&nbsp;&nbsp;&nbsp;&nbsp; exit 1 ;;<br>esac''<br><br>''read -p "enter a single digit: " digit<br>case $digit in<br>&nbsp; [0-9]) echo "Your single digit is: $digit" ;;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; *)&nbsp;echo "not a valid single digit"<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; exit 1 ;;<br>esac''<br><bru>Examples</li><liu>'''The getopts function:'''<br><br></li></ul>The getopts function allows the shell scripter to create scripts that accept options (like options for Linux commands). This provides the Linux administrator with scripts that provide more flexibility and versatility. A built-in function called ''awk 'getopts{print}''' (idata-file.e. get command options) is used in conjunction with a '''while''' loop and a ''txt'case''' statement to carry out actions based on if certain options are present when the shell script is run. The variable '''$OPTARG''' can be used if an option accepts text (denoted in the getopts function with an option letter followed by a colon. Case statement exceptions use the ''':)''' and '''\?)''' cases for error handling.<br><br>''awk -F";" '<u>Example of getopts</u>{print $5,$3}'data-file.txt'' (try in script and run with options)<br><br>''while getopts abc: name<br>do<br>&nbsp; case $name in<br>&nbsp; &nbsp; a) echo awk -F"Action for option \,"a\"" ;;<br>'$4 &nbspgt; &nbsp#61; b) echo "Action for option \"b\"" ;;<br>&nbsp; &nbsp; c) echo "Action for option \"c\""<br>&nbsp; &nbsp; &nbsp; &nbsp; echo Value is: 10000 {print $OPTARG" ;;<br>&nbsp; &nbsp; :) echo "Error: You need text after -c option"<br>&nbsp; &nbsp; &nbsp; &nbsp; exit 1 ;;<br>&nbsp; &nbsp; \?) echo "Error: Incorrect option"<br>&nbsp; &nbsp; &nbsp; &nbsp; exit 1 ;;<br>esac, $2}' salary.txt''<br/li><br/ul>}}

We will now use This emphasis on this section focuses on how to run useful shell scripts or shell scripting script that we have created at specific dates/times. It would be silly to help automate the task for expect a Linux adminstrator system administrator to create regular user accountsstay up late (eg. 2 a.m.  #Download, study, and ) to manually run the following a shell script. Issue the command:<br><b><code><span style=" pointerto terminate processes or to re-events:none;cursor:default;color:#3366CC;font-size:1.2em;">wget https://scs.senecacboot Linux servers.Database files (tables) are used to provide instructions onhow frequent shell scripts or commands can be run.ca/~murray.saul/user-create.bash</span></code></b>#Try The '''cron''' daemon is used to refer to understand what these Bash Shell scripts do, files and then to run the script as rootthem on a pre-determined basis. After running the shell script, view the contents of The term '''cron''' comes from the old word '''chronograph'''meaning a special type of watch (actually a '/home'stop-watch'' directory ) to confirmhelp monitor and schedule routine tasks.

<li value="85">Save, Quickly view the tutorial about the <b>[http://code.tutsplus.com/tutorials/scheduling-tasks-with-cron-jobs--net-8800 Using crontab]</b> file to understand the purpose of this file and how to basically set permissions, and then up a schedule to run that a shell script .</li> <li>Issue the following command to setup a crontab entry for root:<br><b><code><span style=" pointer-events:none;cursor:default;color:#3366CC;font-size:1.2em;">crontab -e</span></code></b></li><li>Enter the input text file following line in order to run at 6:00 on the first day of every month:<br><b><code><span style=" pointer-events:none;cursor:default;color:#3366CC;font-size:1.2em;">0 6 1 * * /root/monitor-disk-space.bash #Runs first day of each month (6:00 am)</span></code></b></li><li>'''user-data.txtSave'''the crontab entry. Did it work? Try running the script without an argument - What did it do? </li><li>You have completed lab4. Proceed to Completing The Lab, and follow Confirm that the entry was properly saved by issuing the instructions for following command:<br><b><code><span style="lab signpointer-offevents:none;cursor:default;color:#3366CC;font-size:1.2em;".>crontab -l</span></code></b></li></ol>

= LAB 4 5 SIGN-OFF (SHOW INSTRUCTOR) ={{Admon/important|Time for a new backup, INCLUDING YOUR VIRTUAL HARD DRIVE!|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 <br><br>''centos1'' Virtual hard-- you now have two virtual disks on ''centos1'', and therefore two drives created in this lab are image files, and therefore will now need two backup filesto be backed up as well!'''.}}

::<ol><li><span style="color:green;font-size:1.5em;">&#x2713;</span> Account created on '''centos1centos2''' VM.::<span style="color:green;font-size:1.5em;"blockquote><ul><li>&#x2713;'''Logical Volume''', '''Physical Volume''', and '''Volume Group''' information </spanli><li> List contents Contents of '''/etc/groupfstab''' file (ops235 group) on </li><li>Proof that '''centos1/archive''' VM.::has been mounted</li></ul></blockquote><li><span style="color:green;font-size:1.5em;">&#x2713;</span> List contents '''centos3''' VM:<blockquote><ul><li>Proof of virtual hard disk creation</li><li>'''Logical Volume''', '''/etc/passwdPhysical Volume''' file (created accounts) on , and '''centos1Volume Group''' VM.::information </li></ul></blockquote></li><li><span style="color:green;font-size:1.5em;">&#x2713;</span> Display current run-level status on '''centos2c7host''' VM.Machine:<blockquote><ul><li>Proof of creation of the shell script:'''monitor-disk-space.bash'''</li><li>Crontab entry for '''root''' account</li></ul></blockquote><li><span style="color:green;font-size:1.5em;">&#x2713;</span> Creation of your bash shell script called '''createUsers.bashLab5'''log-book filled out.</li></ol> 

= Preparing for the = Practice For Quizzes , Tests, Midterm &amp; Final Exam ==

# Describe all of the field in <code>'''/etc/passwd'''</code># What is the command to create a userVG? What option to create a home directory for that userPV? LV?# What is the command to change total size of the full name of an already-created user"main" VG on your system?# What is the command to delete a user account? What option allows for the user's home directory to be removed as wellHow do you create an LV?# What is the command to create a group? What is the command (or steps) to include a user in a newly-created groupHow do resize an LV?# What is How would you add the purpose of <code>disk partition '''/etcdev/shadowsdb7'''</code>to your volume group "main"?# What is How would you increase the purpose size of <code>'''/etc/skel'''</code>the root filesystem by 50 MB?# What does the term run-level meanHow can you determine if a partition has been mounted onto a system?# How to set can you unmount an existing partition from the runfile-level of a Linux system to text-based only? # How to set to graphical modecan you temporarily mount a partition on a file-system?# What is the command to view the status of running servicesHow can you permanently mount a partition on a file-system upon boot-up?# What is are the command to start a service separate elements (like httpd, or sshdfields)of the '''/etc/fstab''' file?# What is Describe the command tools that a Linux system administrator have to start a service?# Can a service be stopped and started by issuing just one command?monitor disk space usage.