Linux links

3. Create a yaml file to be used to run a playbook. Example apache.yml. Please note the first line is 3 dashes. Spacing is CRUCIAL in ansible YAML files. DO NOT USE TAB key! Highly suggest using vim with modified .vimrc file (SEE BELOW) or Visual Studio Code with Ansible extensions installed (easiest since shows spacing graphically)

Install VIM .

a) dnf -y install vim

b) cd ~ or cd

c)To make vim able to detect YAML syntax errors, edit the .vimrc file command below:

vim .vimrc

Put the following 2 lines in .vimrc and save and exit.

autocmd FileType yaml setlocal et ts=2 ai sw=2 nu sts=0
set cursorline

d) vim apache.yml

—

– name: playbook

hosts: webservers

tasks:

– name: Install httpd

dnf:

name: httpd

state: latest

– name: start services

service:

name: httpd

enabled: true

state: started

4. Run the playbook

ansible-playbook apache.yml -i /etc/ansible/hosts

5. Test to see that the remote webserver(s) are installed on the remote host.

ssh root@192.168.1.100

systemctl status httpd

Backup

Linux Bare Metal Restore info

Bare Metal Restore

Notes of bare metal recovery

55187 Linux Backup lab by David Papkin

Firewall

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/security_guide/sec-using_firewalls

https://phoenixnap.com/kb/iptables-tutorial-linux-firewall

CentOS / Redhat Iptables Firewall Configuration Tutorial

Ubuntu Basic iptables howto

Ubuntu Iptables: How to Control Network Traffic Using iptables?

Graphical Admin tools

An introduction to Cockpit

Managing systems using the RHEL 8 web console

How to Install Webmin on CentOS 7

How to Install Latest Webmin on Debian 10/9/8

Web-based interface for system administration

Hypervisor

How to Install Linux in VirtualBox

Downloads – Oracle VM VirtualBox

How to Install Apache Server and Set Up Virtual Hosts on Ubuntu 22.04

https://www.wikihow.com/Install-VirtualBox

Virtual Box Documentation

How to Fix “VT-X Is Not Available (verr_vmx-No-Vmx)” Error in VirtualBox

Install Linux on Windows with WSL

How To Install KVM Hypervisor on Ubuntu 22.04|20.04

MAC Hypervisor

UTM https://mac.getutm.app

List of iso that prepared but can install others https://mac.getutm.app/gallery/

Visit the official CentOS website download page

https://www.centos.org/download/

Ubuntu downloads

https://ubuntu.com/download

Kali downloads

https://www.kali.org/get-kali/#kali-platforms

Monitoring

https://www.tecmint.com/command-line-tools-to-monitor-linux-performance/

https://www.thegeekstuff.com/2011/12/linux-performance-monitoring-tools/

https://www.cyberithub.com/steps-to-install-iostat-mpstat-command-on-linux-rhel-centos-7-8/

How to install htop on CentOS 8

How to install ioping on Ubuntu

How To Check For Open Ports in Linux With netstat, lsof And nmap

See Bandwidth Usage Per Process With Nethogs Tool

How to Monitor Network Traffic using nethogs

NetHogs – Monitor Per Process Network Bandwidth Usage in Real Time

Networking

What happened to eth0? Predictable Network Interface Names

How can I change the default “ens33” network device to old “eth0” on Fedora 19?

Change default network name (ens33) to “eth0” in Centos7/RHEL7

How to change a network interface name on CentOS 7

Password reset

How to Reset Forgotten Ubuntu Password in 2 Minutes

How To Recover Root Password In RHEL/CentOS In 5 Minutes?

Reset root Password Centos/Redhat (challenging)

Patching

Ultimate guide to linux patch management

Patch Management Best Practices

10 Linux Hardening & Security Best Practices

40 Linux Server Hardening Security Tips [2021 edition]

Permissions

Linux permissions: SUID, SGID, and sticky bit

Controlling file permissions with umask

Recycle Bin

Trash-cli – A Trashcan Tool to Manage ‘Trash’ from Linux Command Line

Scripting

Create this sample.sh file with vim or nano
chmod 700 sample.sh
./sample.sh
cat file1.txt

This will output all commands to file1.txt

sample.sh

#!/bin/bash

exec > file1.txt

pwd

ls -l

sample.sh

#!/bin/bash

pwd > file1.txt

ls -l >> file1.txt

Writing Shell Scripts

Software packages

How To Set Up Local Yum Repositories On CentOS 7

CentOS / RHEL : How to create and host yum repository over httpd

Configuring Yum and Yum Repos (REDHAT Docs)

Security

Apache in a chroot jail

Storage

GRUB 1 bootloader – Full tutorial

GRUB 2 bootloader – Full tutorial

Linux FHS

Understanding File System Superblock

Redhat LVM management

Linux LVM Logical Volume for CentOS 7 / RHEL 7

You can monitor RAID devices multiple ways as in:

$ sudo mdadm --detail /dev/md0
$ cat /proc/mdstat

One can also use mdmonitor which requires configuring /etc/mdadm.conf.

The command:

$ sudo mdadm --detail /dev/mdX

will show the current status of the RAID device /dev/mdX. Another way to do this is to examine the /proc filesystem:

$ cat /proc/mdstat

Timezones

Q How to set the timezone to Singapore?

A timedatectl set-timezone Asia/Singapore

timedatectl status

User Mgmt

Gecos field

Assorted

Linux and the GPL

GNU General Public License (GPL) v2.0

Is Linux kernel free to modify?

What’s the version of my OS?

How to Configure ACL(Access Control Lists) in Linux FileSystem

NTUC evaluation

Q & A

Q How to check resource usage for a server twice per hour?

A vmstat 1800 2

Q How to tell the status and current RAID level of your Linux software RAID array?

sudo bash -c mdadm –detail –scan

cat /proc/mdstat

How to check your RAID volume md0?

mdadm –query /dev/md0

How to check that status of an individual disk in a RAID array?

mdadm –examine /dev/sdb2 (if sdb2 is the disk you want to check)

How to list logical device in Logical Volumes in lv012?

lvdisplay -v /dev/vg00/lvol2

Q How to troubleshoot in Linux?

The following list represents the basic steps in a troubleshooting methodology:
• Identify the problem.
• Determine the scope of the problem.
• Establish a theory of probable cause/question the obvious.
• Test the theory to determine the cause.
• Establish a plan of action.
• Implement the solution or escalate the issue.
• Verify full system functionality.
• Implement preventive measures.
• Perform a root cause analysis

How to check a physical volume that is using Logical Volume Manager?

pvdisplay /dev/ssd3

Q How to show the usage of process that are consuming network bandwidth?

a) You can use the nethogs utility.

ex nethogs -a

nethogs -i ens33 or whatever interface you want to get usage stats from.

b) you can use vnstat utility

vnstat -i ens33

vnstati -s -i ens33 -o vnstatreport.png

Q How to know what ports a server is listening to?

A lsof -i -P -n | grep LISTEN

Q How to see what active connections from the Internet?

A netstat –listen

Q How to use iptables

a) Display Your Firewall status

iptables -L -n -v

b) Display firewall with line numbers

iptables -n -L -v –line-numbers

c) Display INPUT or OUTPUT chain rules

iptables -L INPUT -n -v
iptables -L OUTPUT -n -v

d) Stop / Start / Restart the Firewall

service iptables stop/start/restart

e) Drop all incoming / forwarded packets, but allow outgoing traffic

iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT
iptables -A INPUT -m state –state NEW,ESTABLISHED -j ACCEPT
iptables -L -v -n

Q How to install an Apache web server on a Linux Virtual Machine?

Create a new virtual machine and select a Linux distribution, such as Ubuntu or Centos.
Click on the “Create” button and select the following settings:
- Operating System: Linux
- Version: Ubuntu (64-bit)
- Name: Your web server name
- Memory: 2 GB
- Hard Disk: 20 GB
Click on the “Create” button to create the virtual machine.
Once the virtual machine is created, start it up.
The virtual machine will boot up and you will be presented with a screen asking you to select a language. Select your language and click on the “Continue” button.
The virtual machine will now start installing the operating system. This process may take a few minutes.
Once the operating system is installed, you will be presented with a login screen. Enter the username and password that you created during the installation process and click on the “Log in” button.
Once you are logged in, open a terminal window.
Install the Apache web server package by running the following command:

sudo apt install apache2
or
dnf install httpd

Type echo “Welcome to my website” >> /var/www/html/index.html
The Apache web server will be installed and started automatically. You can verify this by opening a web browser such as Firefox and navigating to the http://<your IP address>of the virtual machine or http://localhost
To add a website to the web server, create a new directory in the /var/www/html directory and add your website files to it.
To update the software packages on the web server, run the following command:

sudo apt update && sudo apt upgrade

This will update all of the software packages on the web server to the latest versions.

Security

6 Steps to Assess your Network Security

Follow these six steps to assess the vulnerability of your network:

Step 1: Identify and understand the way your business is organized and operates

Most businesses rely on collaboration between representatives from their internal business units, legal teams, and finance departments to coordinate with IT professionals regarding their exact network needs. Consider issues such as client or customer privacy, regulatory compliance, business processes, and competitive positioning within your industry.

Step 2: Locate the applications and data that are used during the business process

Identify which of these are sensitive and what information is at risk in the event of a privacy breach.

Step 3: Search for hidden data sources that may allow easy access to secure information

This is especially important if there is cloud-based access to private data or access across multiple platforms, including smartphones and tablets.

Step 4: Identify both virtual and physical servers that run applications necessary for your business operations

These servers may not be protected and may allow access to sensitive information without you knowing it.

Step 5: Keep track of what security measures are already in place

Your network protection may already include specific policies, firewalls, virus detection, VPNs, disaster recovery, and encryption. It’s important to understand the capabilities of your current security measures in order to properly address any vulnerabilities.

Step 6: Scan your network for vulnerability

The results of this scan will give you confirmation of your network’s security. Should a virus or vulnerable area be identified, you will need to develop a network security strategy, possibly with the help of an MSP. There are many tools to scan for vulnerabilities.
- https://www.breachlock.com/resources/blog/top-5-open-source-tools-for-network-vulnerability-scanning/
- https://www.techtarget.com/searchsecurity/definition/vulnerability-scanning

IS Standard and Frameworks

Linux Authentication: PAM Tool

Name some Linux Security Tips and Checklist

Click link below to download IAR file. Fill in your Full NRIC Name and Mobile Number ans SIGN it. Please rename file with your NRIC name.

Click link below to upload the filled in and signed form

https://www.dropbox.com/request/QGdBQ1kE7C83eqvQNjR5

http://tinyurl.com/linux221223

DavidontheCloud.com – David Papkin Technical Resources

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