February 28, 2022.
author : Marouane Benbajja - MAR BEN.
- Virtualization a modern technique began in late 1960s it wasn’t widely adopted until the early 2000s. It means to create a version of something, including virtual platforms, devices and computer network resources.
- Hardware virtualization or platform virtualization is creating a virtual machine that acts like a real computer with an OS (operating system). The software executed in these VM is separated form the hardware resources. In hardware virtualization the host machine is the machine that is used by the virtualization - the bare machine that you use (your computer, server, ...) - and the guest is the VM - that runs the guest OS in your machine -. The host ⇒ Software that runs the physical machine. The guest ⇒ Software that runs the VM. The software or firmware that creates the VM on the host machine is called a hypervisor or virtual machine monitor.
- Virtual machine, is the concept of installing an operating system that expects that is installed on a real computer. The VMs behaves exactly like real computers (physical computers) and depends on a virtual resources that are provided by the host machine (the machine where the VM is running). The virtual resources reserves part of the physical resources to provide it to the guests ( the hosted virtual machines ), the resources are isolated from the system hardware, this concept is made by a software called hypervisor.
- Hypervisor is a software, known as a virtual machine monitor, that runs VMs. A hypervisor allows to one host physical machine to supports multiple guest by sharing its resources, such as memory and processing.
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Benefits of hypervisors :
- Speed : It allow to create VMs instantly.
- Efficiency : It minimize the cost and energy by allowing to install several VMs on one physical machine resources and more efficient use of the physical machine.
- Flexibility : Bare-metal hypervisors allow VM’s OS and their Apps to run on variety of hardware types, because the hypervisor separates the OS form the main hardware, so the software doesn’t relies on specific hardware.
- Portability : The isolation, from the physical machine, that the hypervisor can provide to the multiple VMs resided in the host gives the portability capacity. When an application needs more processing power, the virtualization software allows it to seamlessly access additional machines.
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Types of hypervisors :
- Type 1 (bare metal) : Acts like a lightweight operating system and runs directly on the host hardware, so there is no other layer between the hypervisor and the hardware, it is more secure and isolated from the attack-prone operating system and perform better and more efficiently. For these reasons it is usually used for data center computing needs.
- Type 2 (hosted) : Called hosted because they run on top of operating system of the host machine, they are a software run on a the host OS, additional OS can be installed on top of hypervisor (VMs). The latency of this type is higher than the first one, because the communication between the hardware and hypervisor pass through extra layer of the OS. This type is known as client hypervisors, it is usually used with end users where higher latency doesn’t matter.
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How does a hypervisor work :
Hypervisor supports the creation and management of VM by abstracting a computer’s software from its hardware. By translating requests from physical to virtual resources (CPU, RAM, and network) and vice versa, hypervisors make virtualization possible.
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- They are two based OS on Linux.
- Comprehensive installer and easy upgrading
- Supports many architectures
- Has more packages
- Debian is fast catching up
- DEB package format & dpkg/APT as package manger
- EXT4 filesystem & ext2/3, NFSv3/4, SMB, GFS2, ZFS and many more
- Debian uses advanced packaging tool (apt) to manage packaging system.
- Hard To update
- More stable and supported by a large community
- RPM package format & YUM/DNF as package manger
- XFS filesystem & ext2/3, NFSv3/4, btrfs, SMB, GFS2 and many more
What is LVM ? What is a partition table ? What is the difference between primary and logical partitions ? What is a mount point for partition ?
- LVM stand for Logical Volume Manager. It is a type of storage virtualization that allows managing logical volumes, filesystem, it is more advanced and flexible than the traditional whys of partitioning disks then formatting that with filesystem. It can be used for nearly any mount point except
*/boot*.- 3 concepts that LVM manages :
- Volume groups : The collection of physical and logical volumes that can be named.
- Physical volumes : Any physical storage device HDD, ..., or partition, that has been initialized as a physical volume with LVM.
- Logical volumes : flexible volume that Can be extended and reduced, provided by the LVM.
- 3 concepts that LVM manages :
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Package manager is a software that manages, installs, uninstalls, and upgrades packages in Linux and UNIX environments. Packages are collection of files that are bundled together and can be installed or removed as a group (that can be apps, software or other files ...).
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Package A depends on upon another package B : B is required for A to operate properly.
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If a package A recommends another package B : B provides important additional functionality to A desired in most situations.
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If a package A suggests another package B : B provides functionality may enhance A.
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If a package A conflicts with another package B : The two packages can’t be installed at the same time.
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If you want to check the installed packages in Debian :
dpkg -l #it lists all installed packages dpkg -l | grep package #Then it greps the line and displayge the package if it existes
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Debian uses advanced packaging tool (apt) to manage packaging system.
- APT : command line without GUI (graphical user interface) and simple, using apt + install + package name; is enough to let apt do all the other work by searching sorting and installing dependencies for that package.
- APTITUDE : high level package manager, is front-end to advanced packaging tool which adds a user interface to the functionality. It allow to the user to interact searching for packages, install or remove it. Created for Debian extends its functionality to RPM (package manger) base distribution as well.
- Vaster and integrates functionalities of apt-get and it’s other variants apt-mark , apt-cache... (Aptitude ≥= Apt ≥= Apt-get + Apt-mark ....).
- Aptitude handles lot more stuff than Apt, including functionalities of apt-mark and apt-cache...
- Aptitude has a interactive interface along with option of command-line operation by entering required commands.
- Aptitude automatically removes unused packages.
- Aptitude offers ‘why’ and ‘why not’ command
- Aptitude suggests which package should you install or dependencies of other packages
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AppArmor is a Mandatory Access Control (MAC) system which is a kernel (LSM) enhancement to confine programs to a limited set of resources. AppArmor's security model is to bind access control attributes to programs rather than to users. AppArmor confinement is provided via profiles loaded into the kernel, typically on boot.
N.B : AppArmor confines programs according to a set of rules that specify what files a given program can access. Apparmor is used in Debian and Ubuntu distributions.
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To view AppArmor’s status :
sudo apparmor_status
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SE-Linux; Security-Enhanced Linux is a security architecture for Linux systems that allows administrators to have more control over who can access the system. SELinux defines access controls for the applications, processes, and files on a system. SE-Linux is used in Cent_Os.
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sudo, which is an acronym for “superuser do” or “substitute user do”, is a command that runs an elevated prompt without a need to change your identity. Depending on your settings in the
*/etc/sudoers*file. Using sudo command require the user’s password. The sudoers privileges are specified in the*/etc/sudoers*file, so you can give every user or group privileges that you want, by run the following command and edit the file:📁 username ALL=(ALL) ALL //gives user "username" sudo access %wheel ALL=(ALL) ALL //Gives all users that belong to the wheel group sudo accesssudo vi /etc/sudoers
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Why sudo? sudo is used to avoid using root user in your administrating staffs. Small mistake with the root user can be costly and it’s an irreversible step. So you need a solution that is sudo, that provides a simple user with the root power.
Is an acronym for switch user or substitute user. It is a command used to switch to a particular user, you need to enter the user’s password, unless you are root.
su - #switch to the root su username #switch to the user that have username
- Login as root :
su - #You log as a root- Update and upgrade the software repository list, then install sudo :
apt-get update -y apt-get upgrade -y apt install sudo
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SSH, also known as Secure Shell or Secure Socket Shell, is a network protocol that gives users, particularly system administrators, a secure way to access a computer over an unsecured network. In addition to providing strong encryption, can also be used to create secure tunnels for other application protocols. An SSH server, by default, listens on the standard Transmission Control Protocol (TCP) port 22.
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The most basic use of SSH is to connect to a remote host for a terminal session. The form of that command is the following:
ssh UserName@SSHserver.example.com # if you want you add the port ssh UserName@SSHserver.example.com -p port_nbrThis command will cause the client to attempt to connect to the server named server.example.com, using the user ID UserName.
If this is the first time negotiating a connection between the local host and the server, the user will be prompted with the remote host's public key fingerprint and prompted to connect, despite there having been no prior connection:
The authenticity of host 'sample.ssh.com' cannot be established. DSA key fingerprint is 01:23:45:67:89:ab:cd:ef:ff:fe:dc:ba:98:76:54:32:10. Are you sure you want to continue connecting (yes/no)?
Answering with yes; the session continues and the host key is stored in the local system's known_hosts file. This is a hidden file, stored by default in a hidden directory, called
*/.ssh/known_hosts*, in the user's home directory.sudo apt-get update #update the software repository list sudo apt install openssh-server #install ssh server sudo service sshd status #Checking ssh service* status should be active sudo systemctl status ssh #Checking ssh server* status
- To stop, start or restart the ssh service :
sudo service ssh stop #Stopping lasts until the next reboot. sudo service ssh start sudo service ssh restart- Get the IP address :
ip a sudo ifconfig #to use ifconfig you should install net-tools by: sudo apt-get install -y net-tools- How to config the default port
- Enter this file
/etc/ssh/sshd_configusing following command.
- Enter this file
sudo vim /etc/ssh/sshd_config #use nano if vim isn't installed yet→ find this line : #Port 22 → Then change it to : Port 4242sudo service ssh restart #restart the ssh's service* sudo systemctl restart ssh #restart the ssh's server*
- Quit connection if you were connected to a machine via ssh:
exit
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For the longest time, the security of Linux was in the hands of iptables. They are powerful but complicated at the same time especially for new users. Wherefore the UFW (Uncomplicated Firewall) is coming as a front end for iptables to simplify working with it. UFW provides a much more user-friendly framework for managing netfilter and a command-line interface for working with the firewall. UFW has a few GUI tools too.
- Iptable is a Linux command line firewall that allows system administrators to manage incoming and outgoing traffic via a set of configurable table rules, using a set of tables which have chains that contain set of built-in or user defined rules. Thanks to them a system administrator can properly filter the network traffic of his system.
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Installing UFW :
sudo apt-get install ufw
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Enabling UFW :
sudo ufw enable -
Configure the rules :
sudo ufw allow ssh #allowing port for ssh sudo ufw allow 4242 #allowing port 4242
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Check the UFW status :
sudo ufw status #Check the ufw status and its rules sudo ufw status verbose #Same as command above + default firewall setting sudo ufw status numbered #Same as the first, with numbred rules
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Delete a rule :
sudo ufw status numbered sudo ufw delete nbr_of_rule
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Go to VirtualBox-> Choose the VM->Select Settings
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Choose “Network”-> “Adapter 1"->”Advanced”->”Port Forwarding”
- Enter the values as shown:
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Password expiration :
sudo nano /etc/login.defs #open the file, use vim if already installed- Find this path :
PASS_MAX_DAYS 9999 PASS_MIN_DAYS 0 PASS_WARN_AGE 7 #Change values to what you want PASS_MAX_DAYS 30 #max days of password expiration 30 day PASS_MIN_DAYS 2 #min days possible to change password before expiration PASS_WARN_AGE 7 #min days to receive a notification before expiration
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If you created users before setting this configurations, their password expiration wouldn’t be configured. So you should configure it manually using
**chage**command- The
chagecommand changes the number of days between password changes and the date of the last password change. This information is used by the system to determine when a user must change the password.
chage -l user #displays the user password expiring properties sudo chage -M 30 user #changes the max days of expiration sudo chage -m 2 user #changes the min allowed days to change password
- The
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To manage password policy you need the password quality checking library (libpam-pwquality), so it must be installed first
sudo apt-get install libpam-pwquality
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After installation, you will start implementing the password policy. There is two ways to do that.
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The first way → using
*/etc/pam.d/common-password*file :sudo nano /etc/pam.d/common-password #use vim if it is already installed- To edit the minimum password length :
#Search this line password [success=2 default=ignore] pam_unix.so obscure sha512 #Add the minlen password [success=2 default=ignore] pam_unix.so obscure sha512 minlen=10
- To modify the number of time to retry wrong password :
#Search this line password requisite pam_pwquality.so retry=value #Change the retry's value to what you want password requisite pam_pwquality.so retry=3
- To configure the character configuration :
#Search this line password requisite pam_pwquality.so retry=value #Add the options : lcredit=-1 #At least 1 lower case character. ucredit=-1 #At least 1 upper case character. dcredit=-1 #At least 1 digit character. maxrepeat=3 #The max number of consecutive identical characters. usercheck=0 #The password shouldn't contain the username. enforce_for_root #Same policy for root users difok=7 #At least 7 characters different of the old password .
- The file must be look like that :
password [success=2 default=ignore] pam_unix.so obscure sha512 minlen=10 password requisite pam_pwquality.so retry=3 lcredit=-1 ucredit=-1 dcredit=-1 maxrepeat=3 usercheck=0 enforce_for_root difok=7
- Save the file.
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The second way → using
*/etc/security/pwquality.conf*file :sudo nano /etc/security/pwquality.conf #use vim if it is already installed- You will find all options commented and explained their role you need just to uncomment those you want and modify value if it’s necessary and save the file. And all the work is done.
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Now reboot all to apply the configurations :
sudo reboot
sudo adduser user_name
#Then it opens a prompt enter the password and complete informations.
sudo useradd user_name-
Adduser command :
- SYNOPSIS :
**adduser** [options] LOGIN - add users to the system according to command line options and configuration information in
/etc/adduser.conf. It is a high level tool. by default choosing Debian policy conformant UID and GID values, creating a home directory with skeletal configuration, running a custom script, and other features.
💡 After executing the adduser command it will automatically opens a prompt asking to enter the password and after entering it you complete user information, user full name, phone...
💡 The ‘adduser‘ is much similar to the useradd command because it is just a symbolic link to it.
- SYNOPSIS :
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Useradd command :
- SYNOPSIS :
useradd [options] LOGIN - In Linux, a ‘useradd‘ command is a low-level utility that is used for adding/creating user accounts in Linux and other Unix-like operating systems.
- SYNOPSIS :
- The
*/etc/passwd*file contains information about the users on the system. Each line describes a distinct user. - How to check all local users :
cut -d: -f1 /etc/passwd💡Some times we need to update or add new password for a user even if already existing or new created (added by useradd), we use passwd command :
sudo passwd user_name #It displays a prompet to enter and comfime the new password- SYNOPSIS : **
passwd** [*options*] [*LOGIN*] - The
passwdcommand changes passwords for user accounts. If the command is executed without username (login), then it will change the current connected user.
🔴 How to delete a user : Only the root or a user with sudo privileges can remove users.
userdel username #delete the user
userdel -r username #delete the user and the user's directory-
To create a new group we use
groupaddcommand :sudo groupadd group_name
- SYNOPSIS :
**groupadd** [OPTIONS] GROUPNAME - When invoked,
groupaddcreates a new group using the options specified on the command line plus the default values specified in the*/etc/login.defs*file. - The command adds an entry for the new group to the
*/etc/group*and*/etc/gshadow*files. Once the group is created, you can start adding users to the group.
💡Only the root or a user with sudo privileges can create new groups.
🔴 How to delete a group : Only the root or a user with sudo privileges can remove groups.
groupdel group_name
- SYNOPSIS :
- To add a user to certain group
sudo usermod -aG group_name username
sudo adduser user_name group_name-
SYNOPSIS : **
usermod** [*options*] *LOGIN* -
After creating a user we have to sometimes change their attributes like password or login directory, add to groups etc. so in order to do that we use the
Usermodcommand. The information of a user is stored in the following files:*/etc/passwd*-*/etc/group*-*/etc/shadow*-*/etc/login.defs*-*/etc/gshad*-*/etc/login.defs*
When we execute
usermodcommand in terminal the command make the changes in these files itself.- Note:
usermodcommand needs to be executed only as a root user.
🔑 -G, --groupsGROUP1[,GROUP2,...[,GROUPN]]]
- Add user to the group -or groups separated by comma without white spaces- assigned after -G option.
-a : --append
- Used only with -G, it appends the user to the group with saving his old old memberships in other groups. If using -G without -a the user will be added to the group but will be removed from the old ones.
getent group group_name #displays the existing users in the group
groups username-
Getent command :
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SYNOPSIS : **
getent** [*OPTION*]... database... key... -
The getent command displays entries from databases supported by the Name Service Switch libraries, which are configured in
*/etc/nsswitch.conf*.- The database may be any of library supported by the GNU C Library; like in our example : group - passwd - shadow....
🔑 To check the group existence use :
getent group
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Groups command :
- SYNOPSIS : **
groups** [*OPTION*]... [*USERNAME*]... - List all groups a user is a member of. Print group memberships for each USERNAME. Run ‘groups’ command without any arguments to display the list of groups associated with the current user.
- SYNOPSIS : **
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To set up our configuration we need to edit the sudoers file
*/etc/sudoers.*sudo nano /etc/sudoers #use vim if is already installed- To set the paths that can be used by sudo:
Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"- Authentication using sudo has to be limited to 3 attempts if an incorrect password :
Defaults passwd_tries=3
- A custom message to be displayed if an error due to a wrong password occurs when using sudo :
Defaults badpass_message="Your message" #Between "" add your message.
- Each action log file has to be saved in the /var/log/sudo/ folder :
Defaults logfile="/var/log/sudo/sudo.log" Defaults log_input,log_output- Enabling TTY mode :
Defaults requiretty
→ Why TTY : tty is a command in Unix and Unix-like operating systems to print the file name of the terminal connected to standard input. It is commonly used to check if the output medium is a terminal. If no file is detected (in case, it's being run as part of a script or the command is being piped)
not a ttyis printed to stdout and the command exits with an exit status of 1.→ In other words, in our example it imposes that the communication with the VM should be with a terminal ⇒ that is equivalent that the communication is between a human and the VM.
→ Require tty: (Why use tty? If some non-root code is exploited (a PHP script, for example), the
requirettyoption means that the exploit code won't be able to directly upgrade its privileges by runningsudo.) -
The file will look like this :
Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"
Defaults passwd_tries=3
Defaults badpass_message="Wrong password, try again!!"
Defaults logfile="/var/log/sudo/sudo.log"
Defaults log_input,log_output
Defaults requiretty
- Save the file.
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To check the current hostname of your VM, use
hostnamectlcommand :hostnamectl #displays all information about the host machine hostname #displays the host name cat /proc/sys/kernel/hostname
- SYNOPSIS : **
hostnamectl**[OPTIONS...] {COMMAND} hostnamectlmay be used to query and change the system hostname and related settings.
- SYNOPSIS : **
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To change the hostname :
- Execute the current command :
sudo hostnamectl set-hostname new_hostname
- Then edit the
*/etc/hosts*file :
sudo nano /etc/hosts #use vim if already installed- Change old_hostname with new_hostname:
#Before editing 127.0.0.1 localhost 127.0.0.1 old_hostname #After editing 127.0.0.1 localhost 127.0.0.1 new_hostname
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The reboot and check :
sudo reboot
#To avoid any problem of signature changing you can change the user the hostname
#will be changed and go bach to the previous user, without rebooting. -
To execute the monitoring.sh script every 10 minutes we should use the crontab (cron table) file.
- Crontab : stand for cron table, consists a list of command each by line, telling
croncommand what and when to run and is stored for users in*/var/spool/cron*. In other words, the crontab is a list of commands that you want to run on a regular schedule. Each user has their own crontab, and commands in any given crontab will be executed as the user who owns the crontab. - Linux Crontab Format :
MIN HOUR DOM MON DOW CMD #This means : MIN Minute field 0 to 59 HOUR Hour field 0 to 23 DOM Day of Month 1-31 MON Month field 1-12 DOW Day Of Week 0-6 CMD Command Any command to be executed. # Note : * == all
- Cron :The
croncommand-line utility, also known as cron job, is a job scheduler on Unix-like operating systems. Users who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals.
- Crontab : stand for cron table, consists a list of command each by line, telling
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Create the monitoring.sh file (it’s better to create it in
*/usr/local/bin/file)*:touch monitoring.sh
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Building the script :
- Architecture :
uname -a- uname : print system information
- -a : print all information, in the following order.
- uname : print system information
- CPU physical :
grep “physical id” /proc/cpuinfo | uniq | wc -l- grep : print lines matching a pattern.
- uniq : report or omit repeated lines.
- wc : print newline, word, and byte counts for each file.
- -l : ******print the newline counts
- vCPU :
grep "processor" /proc/cpuinfo | wc -l- grep : print lines matching a pattern.
- wc : print newline, word, and byte counts for each file.
- -l : ******print the newline counts
- Memory Usage :
free --mega | awk 'NR == 2 {printf("%d / %d MB \t (%.2f%%)\n", $3, $2, $3/$2*100)}'- free : Display amount of free and used memory in the system.
- —mega : show output in megabytes.
- awk : pattern scanning and processing language
- NR == 2 : it is a conditional expression, means if
NR(number of the line) is 2 then the condition is valid and it can execute what comes after. Because we want to take the second line thatfreedisplays where there is the total and used RAM values. - Printf : it works exactly like the C printf.
$2or$3: means the to take the value of the filed number 2 or 3.- → N.B : this whole command is for taking what
freedisplays and search the second line, it will check every line until it finds the line number 2 the it will take the value of the 2nd and 3rd fields, the 3rd is the used RAM while 2nd is the total of RAM, it displays the 3rd then the 2nd then calculate the percentage and display it.
- NR == 2 : it is a conditional expression, means if
- free : Display amount of free and used memory in the system.
- Disk Usage :
df --total -BG | awk '$1 == "total" {printf("%d / %d GB (%d%%)\n", $3, $2, $5)}'- df : report file system disk space usage.
- —total : produce a grand total of all partitions.
- -BG : scale sizes by SIZE before printing them. E.g., `-BM' prints sizes in units of 1,048,576 bytes.
- awk : pattern scanning and processing language.
$1 == "total": the line that contains the “total” word in the first colon- Printf : it works exactly like the C printf.
- df : report file system disk space usage.
- CPU Load :
top -bn1 | grep load | awk '{printf "%.2f%%\n", $(NF-2)}'- top : display Linux tasks.
- -bn1 : Starts top in 'Batch mode', which could be useful for sending output from top to other programs or to a file. In this mode, top will not accept input and runs until the iterations limit you've set with the '-n' command-line option or until killed.
- awk : pattern scanning and processing language.
- Printf : it works exactly like the C printf.
- $(NF-2) == Total number of fields in the line mines 2. The third last field.
- top : display Linux tasks.
- Last Boot :
who -b | awk '$1 == "system" {print $3" "$4}'- who : show who is logged on.
- -b : time of last system boot.
- awk : pattern scanning and processing language.
$1 == "system": the line that contains the “system” word in the first colonPrint: it prints the colons matched after $ sign.
- **LVM Use ****:
lsblk | grep "lvm" | awk '{if ($1) {print "Yes";exit;} else {print "No"}}'- lsblk : list block devices.
- grep : print lines matching a pattern.
- awk : pattern scanning and processing language.
- if after
grepthe host components and return a line that contains an “lvm” word then theawkwill met this line and the if condition will be valid.
- if after
- Connexions TCP :
cat /proc/net/sockstat | awk '$1 == "TCP:" {print $3 " ESTABLISHED"}'- cat : concatenate files and print on the standard output.
- awk : pattern scanning and processing language.
- **User Log ****:
w -h | wc -lorusers | wc -worwho | wc -l- w : Show who is logged on and what they are doing.
- -h : Don't print the header.
- wc : print newline, word, and byte counts for each file.
- -l : print the newline counts.
- who : show who is logged on.
- w : Show who is logged on and what they are doing.
- Network :
- IP :
hostname -I- hostname : show or set the system's host name.
- -I : Display all network addresses of the host.
- hostname : show or set the system's host name.
- MAC addrs :
ip a | grep ether | awk '{print "("$2")"}'- ip a : show / manipulate routing, devices, policy routing and tunnels.
- IP :
- Sudo :
grep COMMAND /var/log/sudo/sudo.log | wc -l
- Architecture :
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The script looks like :
#!/bin/bash arc=$(uname -a) pcpu=$(grep "physical id" /proc/cpuinfo | uniq | wc -l) vcpu=$(grep "processor" /proc/cpuinfo | wc -l) mem=$(free --mega | awk 'NR == 2 {printf("%d / %d MB \t (%.2f%%)\n", $3, $2, $3/$2*100)}') disk=$(df --total -BG | awk '$1 == "total" {printf("%d / %d GB (%d%%)\n", $3, $2, $5)}') lcpu=$(top -bn1 | grep load | awk '{printf "%.2f%%\n", $(NF-2)}') lstboot=$(who -b | awk '$1 == "system" {print $3" "$4}') lvm=$(lsblk | grep "lvm" | awk '{if ($1) {print "Yes";exit;} else {print "No"}}') tcp=$(cat /proc/net/sockstat | awk '$1 == "TCP:" {print $3 " ESTABLISHED"}') log=$(w -h | wc -l) ip=$(hostname -I) mac=$(ip a | grep ether | awk '{print "("$2")"}') sudo=$(grep COMMAND /var/log/sudo/sudo.log | wc -l) wall " #Architecture : $arc #CPU Physical : $pcpu #vCPU : $vcpu #Memory Usage : $mem #Disk Usage : $disk #CPU Load : $lcpu #Last Boot : $lstboot #LVM Use : $lvm #Connexions TCP : $tcp #User Log : $log #Network : IP $ip $mac #Sudo : $sudo cmd"
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Open sudoers file:
sudo visudo
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Add this line:
your_username ALL=(ALL) NOPASSWD: /usr/local/bin/monitoring.sh
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Reboot :
sudo reboot
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Execute the script as su:
sudo bash /usr/local/bin/monitoring.sh- Open crontab and add the rule:
sudo crontab -u root -e- Add at end as follows: (*/10 means every 10 mins the script will show)
*/10 * * * * bash /usr/local/bin/monitoring.sh
#MIN H DOM M DOW CMD
# MIN Minute field 0 to 59
# HOUR Hour field 0 to 23
# DOM Day of Month 1-31
# MON Month field 1-12
# DOW Day Of Week 0-6
# CMD Command Any command to be executed./boot : Boot loader files (e.g., kernels, initrd).
/root : Home directory for the root user.
/home : Users' home directories, containing saved files, personal settings, etc.
/srv : Site-specific data served by this system, such as data and scripts for web servers, data offered by FTP servers, and repositories for version control systems (appeared in FHS-2.3 in 2004).
/tmp : Directory for temporary files (see also /var/tmp). Often not preserved between system reboots and may be severely size-restricted.
/var : Variable files: files where the content of the file is expected to continually change during normal operation of the system, such as logs, spool files, and temporary e-mail files.
/var/log : Log files. Various logs.
[SWAP] : The swap partition serves as overflow space for your RAM. If your RAM fills up completely, any additional applications will run off the swap partition rather than RAM.