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OPS435 Python3 Lab 8

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<font color='red'><u>'''This lab is currently being reviewed. The final version will be ready by November 11, 2019'''</u></font>
= LAB OBJECTIVES =
:0. Review SSH setup and remote shell execution:1. Use Explore the '''Fabric Python library and its command line tool "fab".:2. Create Fabric scripts utilizing Fabric''' program s API to execute administrative define tasks on remote host via Python functions under for the '''Fabricfab''' frameworkcommand.:23. Create python functions using Fabric API Use the '''fab''' command to execute fabric script to perform Linux system administrative pre-defined tasks on controlled remote Linux systemsmachines.
== Overview ==
: Completing this lab will give you Fabric is a taste Python library and command-line tool for streamlining the use of what is involved in automating remote SSH for application deployment or system/network administration tasks. It has two major components::# a command-line interface program called "fab" that lets you execute arbitrary Python functions :# a set of Python APIs that you can use and call in your Python functions to make executing shell commands over SSH much easier. : We will look at and are going use the Fabric API and its '''Fabricfab''' package command to define and execute Python functions (or tasks), to automate interactions with remote Linux machines in this lab. Using Fabric you can automate monitoring, deploying software, and updating many systems at the same time repeatedly.
== REFERENCE ==
| style="border: 2px solid black;" | Category
| style="border: 2px solid black;" | Resource Link
 
|- style="background-color:white;border:none;"
| style="border: 2px solid black;" valign="top"|
:Official '''Fabric''' website
| style="border: 2px solid black;" valign="top"|
:[http://www.fabfile.org/]
|- style="background-color:white;border:none;"
:[https://www.digitalocean.com/community/tutorials/how-to-use-fabric-to-automate-administration-tasks-and-deployments]
|- style="background-color:white;border:none;"
| style="border: 2px solid black;" valign="top"|
:Official '''Fabric''' website
| style="border: 2px solid black;" valign="top"|
:[http://www.fabfile.org/]
|}
: <font color='blue'>Please note that the version of Fabric installed on matrix.senecacollege.ca for this lab is 1.14 and it supports only Python version 2.</font> The Fabric script files we are going to create in this lab have to meet Python version 2.x requirements. (e.g. print is a keyword, not a built-in function in Python 2.x):2. You should have learned some experience on the following topics in OPS235 and or OPS335. Please review them to prepare for some of the tasks activities in this lab::* Configure create and allow configure a regular user to run the sudo commandon a Linux system. :* The man page on configure and manage sudoprivilege for a regular user:* Configure sudoers using the configuration file: /etc/sudoers.visudo command:* Managing critical system log files: /var/log/messagesusing the yum command to install, /var/log/maillogremove, /var/log/secureand update rpm packages
:* Retrieve current firewall setting using the iptables -L -n -v command
= INVESTIGATION 1: Extra VM Setup The Fabric Environment =
: In order to experience The Fabric environment consists of the following components: :# Controller workstation - the machine that has the Fabric package installed and runs the "fab" command:## the Fabric Python Library - the fabric package (already installed on matrix):## the Fabric API - fabric.api:## the Fabriccommand - '''fab''s features ': run Fabric script, name of the script is default to fabfile.py in a realistic way, wethe current working directory unless specified otherwise with the '-f're going option.:## Fabric script: contains fabric environment object value and Python functions (or tasks) to set up several virtual machines (You need at least be executed by the '''fab''' command.:# Remote machine: the target machine on which one or more VM)Fabric tasks will be executed. To begin with they are all going to have :## running the same configuration. Please make sure that each VM has direct network ssh server daemon:## use public key (or password based) authentication for ssh connection with other VMs you wish to control and configure.
== PART 1 - Set up Configure and test your controller workstation ==: In this lab you will use your login account on matrix.senecacollege.ca as your Fabric controller workstation.
: In this lab you will use your existing vm The Fabric package version 1.14.0 has already been installed on matrix.senecacollege.ca. You should have access to the '''centos7fab''' as a workstation command on matrix. Login to control other VMs which we'll call workersmatrix.senecacollege. Later in ca and run the lab, we will try following command to control and monitor your vm in myvmlab using confirm the version of the fabfile we are going to develop. fabric package: Install '''fabric''' using yum. Once it's installed you should have a '<source lang='bash'>fab''' command available. --version</source>: Type the following command to get the command line optionoptions of the fab command:<source lang='bash'>
fab --help
</source>
:You should get something similar to the following:<source lang="bash">
Usage: fab [options] <command>[:arg1,arg2=val2,host=foo,hosts='h1;h2',...] ...
number of concurrent processes to use in parallel mode
</source>
<font color='green'><b>Please note and study the following command-line options as they will be used in some of the activities in this lab::# -H, :# -f, :# -i, :# -l, and :# --port options.:# --user:# --initial-sudo-password-prompt </b></font>
== PART 2 : Connect to VM in myvmlab.senecacollege.ca ==: You should have received an email from ITS containing the following information::* account name: (usually 'student'):* password: (let's assume it is 'P@ssw0rd' for the following instruction in this lab):* port number for SSH access via myvmlab.senecacollege.ca (e.g. 7200): This VM will be used as the remote Linux machine in our Fabric environment. Login to matrix and try the following SSH command to test the connectivity between matrix and your assignment VM:<pre> [raymond.chan@mtrx-node05pd lab8]$ ssh -p 7200 student@myvmlab.senecacollege.ca student@myvmlab.senecacollege.ca's password: Last login: Fri Jul 3 11:06:24 2020 from mtrx-node05pd.dcm.senecacollege.ca</pre>: Once you are on your VM, try the following commands: hostname, id, and df, and record the results for later comparison with the results of other commands:<source lang='bash'>[student@centos7 ~]$ hostnamecentos7[student@centos7 ~]$ iduid=1002(student) gid=1002(student) groups=1002(student),10(wheel)[student@centos7 ~]$ dfFilesystem 1K-blocks Used Available Use% Mounted ondevtmpfs 878260 0 878260 0% /devtmpfs 889792 0 889792 0% /dev/shmtmpfs 889792 9492 880300 2% /runtmpfs 889792 0 889792 0% /sys/fs/cgroup/dev/mapper/centos- Create master Worker image root 38680112 1745524 36934588 5% //dev/sda2 1038336 331228 707108 32% /boot/dev/sda1 204580 11296 193284 6% /boot/efi/dev/mapper/centos-home 18880512 33160 18847352 1% /hometmpfs 177960 0 177960 0% /run/user/1002</source>:Logout from your VM and get back to matrix.:The previous SSH command when executed successfully, created a login shell on the remote machine. If the previous SSH command is followed by a specific bash command, it will be executed on the remote host instead of creating a login shell. Consider the following:<source lang='bash'>[raymond.chan@mtrx-node05pd lab8]$ ssh -p 7200 student@myvmlab.senecacollege.ca 'hostname;id;df'student@myvmlab.senecacollege.ca's password:centos7uid=1002(student) gid=1002(student) groups=1002(student),10(wheel)Filesystem 1K-blocks Used Available Use% Mounted ondevtmpfs 878260 0 878260 0% /devtmpfs 889792 0 889792 0% /dev/shmtmpfs 889792 9492 880300 2% /runtmpfs 889792 0 889792 0% /sys/fs/cgroup/dev/mapper/centos-root 38680112 1745608 36934504 5% //dev/sda2 1038336 331228 707108 32% /boot/dev/sda1 204580 11296 193284 6% /boot/efi/dev/mapper/centos-home 18880512 33160 18847352 1% /hometmpfs 177960 0 177960 0% /run/user/1002</source>:The three shell commands: hostname, id, and df were executed sequentially. Compare the outputs above with the previous results when executing the corresponding commands in the login shell.:Please note that you were asked to provide the user's password for every SSH connection.
==PART 3: Create a new virtual machineSet up SSH login with public key authentication ==: In order for your controller workstation to automate tasks execution on your VM, you need to configure your VM to SSH public key authentication instead of password authentication. You've done this in both OPS235 and OPS335, and allocate for here is a summary on how to do it 1GB of RAM between your account on matrix and 8GB of disk space. Install a Basic Web Server configuration of CentOS in that your VM using the same CentOS .iso file you used for your first machine in this course.:
: Make sure that::* The hostname of the system is '''worker1'''.:* It has Create a static IP address appropriate for new SSH key pair (one private, and one public) under your virtual networkaccount on matrix.senecacollege.:* Create a regular user using your Seneca email name as the user name: [seneca_id]ca. :* Add this new regular user to Once you have both keys, you can use the '''wheelssh-copy-id''' group using command to copy your public key to the student account on your VM, replace the port number with the following commandcorrect value for your VM:<source lang="'bash"'> usermod ssh-copy-id -a i ~/.ssh/id_rsa.pub -G wheel [seneca_id]p 7200 student@myvmlab.senecacollege.ca</source>This will allow : The above command should add the user contents of your pub key to run the '''sudo''' command~/.ssh/authorized_keys under your student account on your VM.:* After installation ensure Verify and confirm that you your account on matrix can access SSH to your VM as 'student'without prompting for a password:<source lang='worker1''bash' >[raymond.chan@mtrx-node05pd lab8]$ ssh -p 7200 student@myvmlab.senecacollege.caLast login: Fri Jul 3 12:46:19 2020 from your main vm using the static IP address you've assigned mtrx-node05pd.dcm.senecacollege.ca[student@centos7 ~]$ exitlogoutConnection to itmyvmlab.senecacollege.ca closed.
[raymond.chan@mtrx-node05pd lab8]$ ssh -p 7200 student@myvmlab.senecacollege.ca 'date;hostname;id'Fri Jul 3 12:55:22 EDT 2020centos7uid=1002(student) gid=1002(student) groups= Set up SSH key login ===1002(student),10(wheel)[raymond.chan@mtrx-node05pd lab8]$</source>: In order for an automated system to be able to connect to If you got similar result as above, you have successfully configure your controller workstation and your VM and administer it - you will need to be able to connect to it using SSH keys. You've done this in both OPS235 and OPS335use public key authentication.
=INVESTIGATION 2 - Running the fab command in ad-hoc mode =: Create a new The fab command relies on SSH key pair (one private, and one public) on your main VM with your to make the connection to the remote machine before executing the intended commands. The fab command can run in ad-hoc mode:<source lang='bash''regular user''' (don't do >fab [options] -- [shell commands]</source>: When running the fab command in ad-hoc mode, it under root)is very similar to running the SSH with commands attached at the end. Once you have both keys, set things up so that== PART 1:* your regular user running non-privileged shell commands on your remote machines ==: In the following example, we use the '''controller VMfab''' can SSH to execute the worker "date", "hostname", and "id" command remotely on our VM as . Try the same regular user without prompting following ad-hoc fab commands and record their results for a password. (ie. add later use, replace the port number with the contents of correct value for your pub key to ~/.ssh/authorized_keys)VM:* your regular user on your <source lang='bash'>[raymond.chan@mtrx-node05pd lab8]$ fab --host=myvmlab.senecacollege.ca --port=7200 --user=student -- 'controller VMdate;hostname;id'[myvmlab.senecacollege.ca] Executing task '<remainder>' can SSH to the worker VM as root without propmting for a password[myvmlab.senecacollege.ca] run: date;hostname;id[myvmlab.senecacollege.ca] out: Fri Jul 3 13:05:39 EDT 2020[myvmlab.senecacollege.ca] out: centos7[myvmlab.senecacollege. ca] out: uid=1002(student) gid=1002(iestudent) groups=1002(student),10(wheel)[myvmlab. add the contents of your pub key to /root/senecacollege.ssh/authorized_keys)ca] out:
== PART 3 - Clone the Workers ==
: We're only simulating the real world where you'd have hundreds of VMs in one or more clouds, but you can just imagine that the VMs you're creating on your computer are actually being created on an Amazon or Microsoft server.
Done.Disconnecting from myvmlab.senecacollege.ca:7200... done.[raymond.chan@mtrx-node05pd lab8]$</source>: '''** Optional **''' Make four clones of Note that there is no password prompting if you complete part 3 successfully, otherwise, the master worker image SSH server daemon on your VM will prompt you've just created. Then make sure that each of them has for a unique IP addresspassword. ThatThe output from the fab's all you're required to change manually. All ad-hoc mode is not much different from the SSH command with shell command attached at the end, however, please note that the other configuration additional information on the workers (inlcuding output from the hostnames) will fab command can be set by Fabric. Normally you would have some kind of automation doing all this cloning very useful for record keeping purpose - what has been done and IP address assignment as well, but we don't have time for that this semesterwhether the commands had been carried out successfully or not.
== PART 2: Make snapshots of all your workers so running privileged commands on remote machines ==: We say that you can easily restore them running an ad-hoc fab command is very similar to the original state after you modify themSSH command with shell commands attached at the end. Let's try both with privileged commands, like the "yum" command.
= INVESTIGATION 2== Run the "yum" command on remote machine with SSH ===: Fabric practice By default, your VM doesn't have the "tree" rpm package installed. You can verify this with the following SSH command (remember to replace the port number with the correct value for your VM):<source lang='bash'>[raymond.chan@mtrx-node05pd lab8]$ ssh -p 7200 student@myvmlab.senecacollege.ca "yum list tree"Loaded plugins: fastestmirrorLoading mirror speeds from cached hostfile * base: We will start with some basicscentos.mirror.colo-serv.net * extras: centos.mirror.colo-serv.net * updates: centos.mirror.ca.planethoster.netAvailable Packagestree.x86_64 1.6.0-10.el7 base[raymond.chan@mtrx-node05pd lab8]$</source>: Please note that the tree package is "Available", but not yet installed. Fabric runs python programs on : Let't try to install the controller and "tree" package with the workersshell command "yum install tree -y":<source lang='bash'>[raymond.chan@mtrx-node05pd lab8]$ ssh -p student@myvmlab. senecacollege.ca "yum install tree -y"Loaded plugins: fastestmirrorYou create an need to be root to perform this command.</source>: Using the "instructionyum" file on your controllercommand to query rpm package doesn't need special privilege, however, and execute it does when you try to install or remove rpm packages. : Your "student" account on your VM was configured to allow you to run the controller "sudo" command to perform software management using the "yum" command. Let's login to your VM and try the following "sudo" command to install and then remove the "tree" rpm package:<source lang='bash'fab''' program>[raymond.chan@mtrx-node05pd lab8]$ ssh -p 7200 student@myvmlab.senecacollege.caLast login: Fri Jul 3 16:51:07 2020 from mtrx-node05pd.dcm.senecacollege.ca[student@centos7 ~]$ sudo yum install tree -y[sudo] password for student:Loaded plugins: fastestmirrorLoading mirror speeds from cached hostfile * base: less.cogeco.net * extras: centos.mirror.colo-serv.net * updates: mirror.calgah.comResolving Dependencies--> Running transaction check---> Package tree.x86_64 0:1.6. When you do that 0- you specify which workers you want your instructions to 10.el7 will be executed on.installed--> Finished Dependency Resolution
: The instructions are stored in a python file. Let's start with a simple one named '''fabfile.py''' (the default filename used by fab without the '-f' optino):Dependencies Resolved
== PART 1: Simplest example ====================================================================================================================== Package Arch Version Repository Size===Getting the hostname on the remote worker=====================================================================================================================Installing: <source lang="python">from fabric tree x86_64 1.6.0-10.api import *el7 base 46 k
# set the name of the user on the remote hostTransaction Summaryenv.name = '[seneca_id]'=======================================================================================================================Install 1 Package
# Will get the hostname of this workerTotal download size:46 kInstalled size: 87 kDownloading packages:tree-1.6.0-10.el7.x86_64.rpm | 46 kB 00:00:00Running transaction checkRunning transaction testTransaction test succeededRunning transaction Installing : tree-1.6.0-10.el7.x86_64 1/1 Verifying : tree-1.6.0-10.el7.x86_64 1/1
def getHostname()Installed: name = run("hostname") print(name)</source> tree.x86_64 0: To check for syntax error, run the following command in the same directory as your fabfile1.py:<source lang="bash">fab -l</source>: you should get a list of tasks stored in your fabfile6.py:<source lang="bash">[rchan@centos7 lab8]$ fab 0-f fabfile10.py -lAvailable commands:el7
getHostnameComplete![student@centos7 ~]$
</source>
: To perform Please note that when you run the task of getHostname on "sudo" command the worker machine 192first time, it asks you for the user's password (i.168e.122user student's password).169, we run it on Let's now remote the controller machine like this"tree" package:<source lang="'bash"'>[rchanstudent@centos7 lab8~]$ fab yum remove tree -f fabfileyLoaded plugins: fastestmirrorYou need to be root to perform this command.py -H 192.168.122.169. getHostname[192.168.122.169student@centos7 ~] Executing task 'getHostname'$ sudo yum remove tree -y[192.168.122.169] runLoaded plugins: hostnamefastestmirrorResolving Dependencies--> Running transaction check[192---> Package tree.168x86_64 0:1.1226.169] out: c70-rchan10.el7 will be erased[192.168.122.169] out: --> Finished Dependency Resolution
c7-rchanDependencies Resolved
Done.========================================================================================================================Disconnecting from 192.168.122.169... done. Package Arch Version Repository Size</source>========================================================================================================================Removing:All this has done is get the hostname of the worker and print it (on the controller).:In the command above we're using the fab program to import the file fabfile.py and execute the getHostname function on the worker 192.168.122 tree x86_64 1.1696. Note that the IP address of your first worker will likely be different0-10.el7 @base 87 k
: If you did all the setup right and you get a password prompt when execute the above command, read the prompt carefully and see who's password it prompted you for. If it is not the same as your [seneca_id], verify that you have the following line in your fabfile and you can ssh to your worker vm without password:Transaction Summary========================================================================================================================Remove 1 Package
Installed size:<source lang="python">env87 kDownloading packages:Running transaction checkRunning transaction testTransaction test succeededRunning transaction Erasing : tree-1.6.0-10.el7.x86_64 1/1 Verifying : tree-1.6.0-10.el7.user = '[seneca_id]'<x86_64 1/source>1
: In the above you haveRemoved::* Lines with an IP address telling you which worker the output is for/from.:* Messages from the controller (e.g. "Executing task.. tree.", and "runx86_64 0: 1.6.0-10.").:* Output from the worker ("out: ..."):* Output on the controller from your fab file ("worker1" which came from the "print()" call)el7
Complete![student@centos7 ~]$</source>:You should get used The above tests confirm that the student user is allowed to run the aboveyum command to install and remove rpm package. ItNow let's logout from the VM and go back to matrix. On matrix, try to run the sudo command using SSH:<source lang='bash'>[student@centos7 ~]$ exitlogoutConnection to myvmlab.senecacollege.ca closed.[raymond.chan@mtrx-node05pd lab8]$ ssh -p 7211 student@myvmlab.senecacollege.ca "sudo yum install tree -y"sudo: no tty present and no askpass program specified[raymond.chan@mtrx-node05pd lab8]$</source>: The above error indicated that you need a lot of output but it's important tty for the SSH session to understand where every part is coming from, so prompt you are able for the sudo password. Please look up the ssh man page to debug problems when they happenfind out the option which turn on a tty for the SSH session.
== Part 2= Run the privileged yum command on remote machine using ad-hoc fab command ===: Let's try the corresponding ad-hoc fab command on your VM:<source lang='bash'>fab --host=myvmlab.senecacollege.ca --port=7200 --user=student -- 'sudo yum install tree -y'</source>: Set up more administrative tasksType in your user student's password when prompted for "sudo password", the yum install command to install the tree rpm package should be executed successfully. If the tree rpm package is already installed, you can remove it with the following ad-hoc fab command: <source lang='bash'>fab --host=myvmlab.senecacollege.ca --port=7200 --user=student -- 'sudo yum remove tree -y'</source>: Try remove the "tree" rpm package with the appropriate ad-hoc fab command.
= INVESTIGATION 3:LetRunning the fab command in script mode =: From investigation 2, we can see that running '''fab'''s pretend that we in ad-hoc mode is quick, straight forward, and easy. However, the rich output generated can not be easily captured and processed. If you have a need collect to capture and process the output generated by the disk usage commands executed on several the remote machines so that we can plan for storage maintenance, the solution is to run the '''fab''' command in script mode.: The first step in running the '''fab''' command in script mode is to create a fabric script file. We: Let'll set up s start with a simple example of such fabric script file to demonstrate some basic concepts that use the API from the Fabric python library.: On matrix, cd to your lab8 directory and create a deployment heresimple fabric script file named '''fabfile.py''' (this is the default filename used by the fab command when you invoke it without the '-f' optino):
==PART 1: Non-privileged task example = ====Create non-privileged tasks: Getting the disk usage on hostname of remote worker machines===: Add the following contents to the default fabric script called "fabfile.py" in your lab8 directory:<source lang="python">from fabric.api import *
:Add a getDiskUsage() function # set the name of the user login to your fabfilethe remote hostenv.py file:user = 'student'
:<source lang="python"># Define the task to get the disk usage on hostname of remote workermachines:def getDiskUsagegetHostname(): current_time name = run('date'"hostname") diskusage = run('df -H') header = 'Current Disk Usage at '+current_time print(header) print(diskusage"The host name is:",name)
</source>
:Note that each call to "To check for syntax error in the fabric script, run()" will run a the following command on in the workerlab8 directory where it contains the fabric script named "fabfile. In this function we py":<source lang="bash">fab -l</source>: you should get the date/time a list of the remote work, and then get the disk usage. The print() function print out both the values returnedtasks defined in your fabfile.py:<source lang="bash">[rchan@centos7 lab8]$ fab -lAvailable commands:
getHostname</source>:If you try To perform the task of getHostname on your VM (replace with the actual port # for connecting to your VM), run it the same way as beforefab command on matrix:<source lang="bash">[raymond.chan@mtrx-node05pd lab8]$ fab --hosts=myvmlab.senecacollege.ca --port=7200 getHostname[myvmlab.senecacollege.ca] Executing task 'getHostname'[myvmlab.senecacollege.ca] run: hostname[myvmlab.senecacollege.ca] out: centos7[myvmlab.senecacollege.ca] out:
<pre>$ fab --fabfile=fabfile.py -H 192.168.122.169 getDiskUsage</pre>The host name is: centos7
:You should get the following output:<source lang="bash">Done.[rchan@centos7 lab8]$ fab --fabfile=fabfileDisconnecting from myvmlab.py -H 192senecacollege.168ca:7200.122.169 getDiskUsage[192.168done.122.169] Executing task 'getDiskUsage'[192raymond.168.122.169chan@mtrx-node05pd lab8] run$</source>: date[192Notice that there is no need to specify the user name at the '''fab''' command line since we defined it in the fabric script file (env.168user = 'student').122.169] Also notice that we can capture the host name returned from the "hostname" command and print it out: Sun Nov 10 13:17:16 EST 2019[192.168.122together with an descriptive text in a line.169] out:
[192.168.122.169] run: df -H[192In the above executed '''fab''' command, the fab program imports the fabric script named "fabfile.168.122.169] out: Filesystem Size Used Avail Use% Mounted py" and execute the getHostname function on the VM connect at port 7200 on[192.168.122.169] out: devtmpfs 947M 0 947M 0% /dev[192.168.122.169] out: tmpfs 964M 0 964M 0% /dev/shm[192.168.122.169] out: tmpfs 964M 9.7M 954M 2% /run[192.168.122.169] out: tmpfs 964M 0 964M 0% /sys/fs/cgroup[192.168.122.169] out: /dev/mapper/centos-root 7.7G 5.6G 2.1G 73% /[192.168.122.169] out: /dev/vda1 1.1G 298M 766M 29% /boot[192.168myvmlab.122senecacollege.169] out: tmpfs 193M 17k 193M 1% /run/user/42[192ca.168Note that the port number for your first will likely be of a different value.122.169] out: tmpfs 193M 0 193M 0% /run/user/1000[192.168.122.169] out:
Current Disk Usage at Sun Nov 10 13:17:16 EST 2019Filesystem Size Used Avail Use% Mounted ondevtmpfs 947M 0 947M 0% /devtmpfs 964M 0 964M 0% /dev/shmtmpfs 964M 9If you did all the setup right and you got a password prompt when execute the above command, read the prompt carefully and see who's password it was prompting you for.7M 954M 2% /runtmpfs 964M 0 964M 0% /sys/fs/cgroup/dev/mapper/centos-root 7.7G 5If it is not for the user student, verify that you have the following line in your fabfile.6G 2.1G 73% //dev/vda1 1.1G 298M 766M 29% /boottmpfs 193M 17k 193M 1% /run/py and you can ssh to your VM as the user/42tmpfs 193M 0 193M 0% /run/user/1000student without password:
Done:<source lang="python">env.Disconnecting from 192.168.122.169... done.user = 'student'</source>
:YouIn the above output from the 'll find that yum prompts ''fab''' command, you to answer questions, which have::* Lines with the FQDN of the remote machine you don't want to do in an automated environmentare working on.:* Messages from the controller workstation (e. And also yum prints too much output, which also isn't helpful in an automated environmentg. We'll fix it by adding two switches to yum: "-yExecuting task..." , and "-d1run: ...").:* Output from the remote machine ("out: ..."):* Output generated on the controller workstation from your fab file (the print statement)
:Notice also that all of the four commands can be run as many times as you want, You should get used to the result will be above messages from the same'''fab''' command. This It's a lot of output but it's important to understand where every part is not always coming from, so easyyou are able to debug problems when they happen.
== PART 2: Privileged Tasks Examples ==
===Creat privileged tasks: install and remove rpm package on remote machines===
: Add the following two new functions to the end of the fabric script "fabfile.py" in your lab8 directory:<source lang='bash'>
def installPackage(pkg='dummy'):
cmd = 'yum install ' + pkg + ' -y'
status = sudo(cmd)
print(status)
def removePackage(pkg): if pkg === Update all the rpm packages on remote worker ===:Let's pretend that we need to update software packages installed on several machines due to security patches. Let's name the task as : cmd = 'performSoftwareUpdate()yum remove dummy -y':<source lang="python"># to perform software update on remote workerdef performSoftwareUpdate() else: status cmd = run('yum update remove ' + pkg + ' -y' status = sudo(cmd)
print(status)
</source>
: Do Note that both functions take one function argument in different ways. However, if no function argument is passed when calling the function, both will default to a syntax check with string value of "dummy". Both functions call the sudo() from the fabric.api to execute the command contained in the "fab -lcmd" commandobject on the remote machine via sudo.: When you try to To check for any syntax error in your updated fabric script, run it the following command in the same way directory as before, you encounter some issue as shown belowthe fabfile.py:<source lang="'bash"'>[rchan@centos7 lab8]$ fab --fabfilel</source>: You should get a list of tasks defined similar to the following:<source lang=fabfile.py -H 192.168.122.169 performSoftwareUpdate[192.168.122.169] Executing task 'performSoftwareUpdatebash'>[192raymond.168.122.169chan@mtrx-node05pd lab8] run: yum update $ fab -y[192.168.122.169] out: Loaded plugins: fastestmirror, langpacksl[192.168.122.169] out: You need to be root to perform this command.[192.168.122.169] outAvailable commands:
getHostname
installPackage
removePackage
[raymond.chan@mtrx-node05pd lab8]$
</source>
: If you only need to connect to the same remote machine, you can specify the host and port number in the fabfile.py to save some typing when executing the fab command. Add the following two lines after the env.user line in your fabfile.py:<source lang='bash'>
env.port = '7200' # <-- please replace with the actual value of your VM's port number
env.hosts =['myvmlab.senecacollege.ca']
</source>
: You can also store the user's password in this file so that it will respond to the "sudo password" prompt for sudo() call. It is not safe to do so as you can configure the sudo module on the remote machine not to ask for sudo password.
: Now you can run the fab command without the "--host" and "--port" option.
: Run the following two fab commands, note the results and compare their difference:<source lang='bash'>
fab installPackage
Fatal errorfab installPackage: run() received nonzero return code 1 while executing!tree</source>: Run the following two fab commands, note the results and compare their difference:<source lang='bash'>fab removePackage
Requestedfab removePackage: yum update -yExecuted: /bin/bash -l -c "yum update -y" Aborting.Disconnecting from 192.168.122.169... done.tree
</source>
: As you already know, you need superuser privilege in order to perform software update on a Linux system. There are two ways to do it on Fabric. The first one is simple. Edit you fabfile.py and change the env.user line as shown below:<source lang="python">
 
env.user = 'root'
== Part 2: Create remote task for updating rpm packages ==
: Add a new function called "updatePackage" to your fabfile.py according to the following requirements:
:* Accept optional function argument as the rpm package name
:* If no function argument was given when called, default to all the packages installed
: The output of the updatePackage when executed, should produce similar output as shown below:
:1. Update a single package:<source lang='bash'>
fab updatePackage:tree
</source>
: Save the fabfileSample output:<source lang='bash'>[raymond.py with the change and run it againchan@mtrx-node05pd lab8]$ fab updatePackage:tree[myvmlab.senecacollege.ca] Executing task 'updatePackage'[myvmlab.senecacollege.ca] sudo: If you see the yum update tree -y[myvmlab.senecacollege.ca] out: sudo password prompt again, make sure that you can ssh :[myvmlab.senecacollege.ca] out: Loaded plugins: fastestmirror[myvmlab.senecacollege.ca] out: Loading mirror speeds from your controller as a regular user to your worker vm as root without passwordcached hostfile[myvmlab.senecacollege.ca] out: * base: less.cogeco.net[myvmlab.senecacollege.ca] out: * extras: centos.mirror.ca.planethoster.net[myvmlab.senecacollege.ca] out: * updates: less.cogeco.net[myvmlab.senecacollege.ca] out: No packages marked for update[myvmlab.senecacollege.ca] out:
== Part 3Loaded plugins: Setting and Checking Security Configuration ==fastestmirrorLoading mirror speeds from cached hostfile * base: less.cogeco.net * extras: centos.mirror.ca.planethoster.net * updates: less.cogeco.netNo packages marked for update
Done.Disconnecting from myvmlab.senecacollege.ca: Recall that in our OPS courses we've been using iptables instead of firewalld, which is installed by default in CentOS7200.. Let's make sure that our workers have that set up as well. In the same '''fabfiledone.py''' you've been using all along, add a new function like this: : <source lang="python"># Will uninstall firewalld and replace it with iptablesdef setupFirewall(): run("yum -y -d1 remove firewalld") run("yum [raymond.chan@mtrx-y -d1 install iptables-services") run("systemctl enable iptables") run("systemctl start iptables")node05pd lab8]$
</source>
 : That should by now look pretty obvious. On the worker you're going to uninstall firewalld, install iptables, and make sure that the iptables service is running2: Execute the function for worker1 and double-check that it worked.Update all installed package: <font colorsource lang='red'>'''**Warning**bash''' </font>Do not do this on your vm on myvmlab. If you do, you may lock yourself out for good. === Check firewall configuration === fab updatePackage: To check your firewall configuration your remote worker, you can retrieve its current configuration by creating another Fabric task called "getFirewallConfigure(). Let's put the following code to your fabfile.py:<source lang="python">def getFirewallConfig(): fw_config = run("iptables -L -n -v") print(fw_config)
</source>
: The following output had been trimmed, only showing the first few lines:<source lang='bash'>
[myvmlab.senecacollege.ca] Executing task 'updatePackage'
[myvmlab.senecacollege.ca] sudo: yum update -y
[myvmlab.senecacollege.ca] out: sudo password:
[myvmlab.senecacollege.ca] out: Loaded plugins: fastestmirror
[myvmlab.senecacollege.ca] out: Loading mirror speeds from cached hostfile
[myvmlab.senecacollege.ca] out: * base: less.cogeco.net
[myvmlab.senecacollege.ca] out: * extras: centos.mirror.ca.planethoster.net
[myvmlab.senecacollege.ca] out: * updates: less.cogeco.net
...
Verifying : Try to run the getFirewallConfig() task the same way as beforesystemd-219-73.el7_8.5.x86_64 53/54 Verifying : Troubleshoot if you encounter any issuesystemd-libs-219-73.el7_8.5.x86_64 54/54
= INVESTIGATION Removed: kernel.x86_64 0:3: Multiplying your work =.10.0-862.el7
Installed: After completing all the previous parts of the lab kernel.x86_64 0:3.10.0- you should have a working fabfile1127.py with two working functions: setupFirewall() and setupWebServer()13.1.el7
'''** Optional **'''You were asked to test them on worker1Updated: bind-export-libs.x86_64 32:9.11.4-16.P2.el7_8.6 binutils.x86_64 0:2.27-43.base.el7_8.1 ca-certificates.noarch 0:2020.2.41-70.0.el7_8 device-mapper.x86_64 7:1.02.164-7.el7_8.2 device-mapper-event.x86_64 7:1.02.164-7.el7_8.2 device-mapper-event-libs.x86_64 7:1.02.164-7.el7_8.2 device-mapper-libs.x86_64 7:1.02.164-7.el7_8.2 kernel-tools.x86_64 0:3.10.0-1127.13.1.el7 kernel-tools-libs.x86_64 0:3.10.0-1127.13.1.el7 lvm2.x86_64 7:2.02.186-7.el7_8.2 lvm2-libs.x86_64 7:2.02.186-7.el7_8.2 microcode_ctl.x86_64 2:2.1-61.10.el7_8 net-snmp.x86_64 1:5.7.2-48.el7_8.1 net-snmp-agent-libs.x86_64 1:5.7.2-48.el7_8.1 net-snmp-libs.x86_64 1:5.7.2-48.el7_8.1 net-snmp-utils.x86_64 1:5.7.2-48.el7_8.1 ntp.x86_64 0:4.2.6p5-29.el7.centos.2 ntpdate.x86_64 0:4.2.6p5-29.el7.centos.2 python-perf.x86_64 0:3.10.0-1127.13.1.el7 rsyslog.x86_64 0:8.24.0-52.el7_8.2 selinux-policy.noarch 0:3.13.1-266.el7_8.1 selinux-policy-targeted.noarch 0:3.13.1-266.el7_8.1 systemd.x86_64 0:219-73. Now let's run these two functions on all your workers at the same timeel7_8. The command is almost the same, except for the list of IP addresses8 systemd-libs.x86_64 0:219-73.el7_8.8 systemd-sysv.x86_64 0:219-73.el7_8.8 yum-plugin-fastestmirror.noarch 0:1.1.31-54.el7_8
<source lang="bash">fab --fabfile=fabfile.py -H 192.168.56.11,192.168.56.12,192.168.56.13,192.168.56.14,192.168.56.15 setupWebServer</source>Complete!
: Again - your IP addresses will be different but the command will be the sameDone: You can also reconfigure the firewall on all the workers at the same time, using a command like this on your controller: <source lang="bash">fab --fabfile=fabfileDisconnecting from myvmlab.py -H 192senecacollege.168ca:7200.56.11,192.168done.56[raymond.12,192.168.56.13,192.168.56.14,192.168.56.15 setupFirewallchan@mtrx-node05pd lab8]$</source> And imagine that you might have 10, 50, 100 servers to do this on - could you do it without the automation?
= Final Task - Apply fabfile.py to your VM on myvmlab Lab Exercise: Create a Fabric task called makeUser() =: Since your account on your vm on myvmlab is a regular user with Study the Fabric API run(), sudo privilege. You need (), and put() and utilize them to make create a new task called makeUser(): The makeUser() function should perform the following changes to your fabfile.py before applying it to your vm on myvmlab::* Change envcreate a new user called "ops435p" with home directory "/home/ops435p".user from 'root' :* add it to your account on your vm in myvmlabthe sudo group called "wheel".:* Change all ask your professor for a ssh public key and add it to the file named "authorized_keys" in the commands ~ops435p/.ssh directory. Make sure that need super user privilege from calling you set the proper permissions on both the run() function to instead calling directory ~ops435p/.ssh and the sudo() functionfile "~ops435p/.ssh/authorized_keys.: Test Add the makeUser() to your updated final version of fabfile.py until you get . :Run the same result as when you apply it to new task makeUser() on your own worker VM.:Verify and confirm that your new makeUser() task is working correctly.
= LAB 8 SIGN-OFF (SHOW INSTRUCTOR) =
:'''Have Ready to Show Your Instructor:'''* Complete all the parts of the lab and show upload the version of your fabfile.py which works on your vm on myvmlabto Blackboard by the due date.  = LAB REVIEW =
[[Category:OPS435-Python]][[Category:rchan]]
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