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''').

*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/vgs.8.php html vgs]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/lvspvs.8.php lvshtml pvs]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/pvslvs.8.php pvshtml lvs]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/vgdisplay.8.php html vgdisplay]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/lvdisplaypvdisplay.8.php lvdisplayhtml pvdisplay]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/pvdisplaylvdisplay.8.php pvdisplayhtml lvdisplay]<br>

*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/lvextend.8.php html lvextend]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/lvcreate.8.php html lvcreate]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/lvreduce.8.php html lvreduce]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/pvcreate.8.php html pvcreate]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/vgextend.8.php html vgextend]<br>

*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/mount.8.php html mount]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8/umount.8.php html umount]<br>*[http://linuxmanpagesman7.comorg/linux/man-pages/man8man1/mountdf.81.php html df ]<br>*[http://man7.org/linux/man-hpages/man1/du.1.html du]<br>*[http://linuxmanpageswww.lehman.cuny.comedu/cgi-bin/man-cgi?awk+1 awk]<br>*[http:/man8/mounttldp.8org/HOWTO/Partition/fdisk_partitioning.php html fdisk]<br>*[http://linuxmanpageswww.cyberciti.biz/faq/howto-format-create-linux-filesystem/ mkfs]*[http://man7.org/linux/man-pages/man5/fstab.5.comhtml /etc/fstab]*[http:/man8/mountcode.8tutsplus.php mkfscom/tutorials/scheduling-tasks-with-cron-jobs--net-8800 Using crontab]

=INVESTIGATION 1: Adjusting File System Sizes with MANAGING FILE-SYSTEMS USING LVM={| width="40%" align="right" cellpadding="10"|- valign="top"|{{Admon/note|VM Backups and Recovery|Most of these investigations will take place in your 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 2, and you can restore them if something goes wrong.<br /><br />'''Remember: if you did not create backups for all of your VMs, then you don't have any restoration points to fall-back to!'''|}}|}Monitoring and ensuring adequate space for a Linux file-system is considered to be a critical task for any system administrator. An application called '''LVM''' is a very useful tool for Linux system administrators to easily manage file systems - even when the computer system is running!

Monitoring and ensuring adequate space for a Linux file-system '''LVM''' ('''Logical Volume Management''') is considered used to be an important task manage hard disk drives / partitions for a sys adminLinux and Unix systems. An application called LVM is 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 very useful tool specific physical volume or for Linux system adminstratorsa "range" or "span" of physical volumes.

'''LVM''' ('''Logical Volume Management''') is used to manage hard disk drives / partitions allows more flexibility and growth potential for Unix/Linux systems. LVM provides more flexibility than just working with hard disks / hard disk partitions. '''Volume Groups''' are areas used to define '''Physical Volumes''' (i.e. for example, having Logical volumes span multiple hard disks, disk partitions, or other forms of storage devices). '''Logical Volumes''' are then used CentOS uses LVM by default upon installation. Other Linux distributions may provide the capacity to relate directories (mount points) to a specific physical volume or for a "range" or "span" of physical volumes.install LVM,

[[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></code></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= Part "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: Obtaining System Information with 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 Graphicallyconfiguration 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>

===Part 2: Obtaining System Information with Because we're using LVM Via Command Line===we can avoid this problem. We can '''add a new <u>virtual</u> hard-drive''' (which will serve as a physical volume) to the volume group, and extend the root logical volume to make use of the new available space. Creating virtual hard drives is not only inexpensive, but a great way for students to learn now to simulate growing the size of the file system.

# xPerform 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>'''</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 1'') to create a new single primary partition for '''/dev/vdb''' that fills the entire disk, save partition table (accepting defaults prompts would work), restart your '''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="color:#3366CC;font-size:1.2em;">vgextend ''name_of_volumegroup'Answer Part 2 observations ' /dev/vdb1</span></code></ questions in your lab log book.'''b>

{| width="40%" align="right" cellpadding=Part 3"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: Adjusting Partition Sizes with <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 Graphically===commands have "safeguards" (eg. option '''-r''' to prevent destroying the file-system (thus making the ''resize2fs'' command <u>obsolete</u>). '''|}}|}

== 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.]]# xPerform this part in your '''centos2''' VM.# As you may recall in Part 1 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 '''/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 logbook, 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!).

= INVESTIGATION = Part 2: CREATING VIRTUAL HARD DRIVES Monitoring Disk Space ==[[Image:disk_usage.png|thumb|500px|right|The '''df''' and '''du''' commands are useful tools for Linux system administrators to flag disk space issues and investigate their causes.]]Another essential duty of a Linux system administrator is to anticipate problems and take preventative measures to avoid computer system problems <u>before</u> that occur.

= INVESTIGATION 43: LOOKING AHEAD =

==Automating Routine Tasks (Scheduling The Running of Shell Scripting and Using Script 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 scripting scripts or shell script that we have created at specific dates/times. It would be silly to expect a system administrator to help automate stay up late (eg. 2 a.m.) to manually run a shell script to terminate processes or to re-boot Linux servers. Database files (tables) are used to provide instructions on how frequent shell scripts or commands can be run. The '''cron''' daemon is used to refer to these files and to run them on a pre-determined basis. The term '''cron''' comes from the task for old word '''chronograph''' meaning a Linux adminstrator special type of watch (actually a ''stop-watch'') to create regular user accountshelp 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>

{{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> x:'''centos2''' VM:<blockquote><ul><li>'''Logical Volume''', '''Physical Volume''', and '''Volume Group''' information </li><li>Contents of '''/etc/fstab''' file</li><li>Proof that '''/archive''' has been mounted</li></ul></blockquote><li><span style="color:green;font-size:1.5em;">&#x2713;</span> x:'''centos3''' VM:<blockquote><ul><li>Proof of virtual hard disk creation</li><li>'''Logical Volume''', '''Physical Volume''', and '''Volume Group''' information </li></ul></blockquote></li><li><span style="color:green;font-size:1.5em;">&#x2713;</span> x:'''c7host''' Machine:<span style="colorblockquote><ul><li>Proof of creation of the shell script:green;font'''monitor-disk-size:1space.5em;"bash'''</li><li>Crontab entry for '''root''' account</li></ul>&#x2713;</spanblockquote><li> x::<span style="color:green;font-size:1.5em;">&#x2713;</span> x'''Lab5''' log-book filled out.</li></ol> 

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

# How do you create a an LV?# How do you delete resize an LV?

# How can you determine if a partition has been mounted onto a system?# How can you unmount an existing partition from the file-system?# How can you temporarily mount a partition on a file-system?# How can you permanently mount a partition on a file-system upon boot-up?# What is are the purpose separate elements (fields) of the '''/etc/fstab'''file?# Describe the tools that a Linux system administrator have to monitor disk space usage.