What’s New in Linux Kernel 5.0?

Linux Kernel 5.0 has been released. Previously earmarked to be version 4.21, the new release comes with an array of improvements (as you’d expect). But don’t expect grand changes just because there’s a natty new version number. Linus Torvalds explains that: “The numbering change is not indicative of anything special. If you want to have an official…

Apache Cloudstack

CloudStack is apache foundation managed open-source cloud computing software for creating, managing, and deploying infrastructure cloud services. It uses existing hypervisors such as KVM, VMware vSphere, VMware ESXi, VMware vCenter, and XenServer/XCP for virtualization. In addition to its own API, CloudStack also supports the Amazon Web Services (AWS) API[2] and the Open Cloud Computing Interface from the Open Grid Forum. Rather than explain CloudStack here. (I am still learning cloudstack). I think your…

ARM Processors land in a Supercomputer – First Petascale supercomputer built by Perspecta [HP] for Sandia Labs.

Sandia National Laboratories will soon be taking delivery of the world’s most powerful supercomputer using ARM processors. The system, known as Astra, is being built by Hewlett Packard Enterprise (HPE) and will deliver 2.3 petaflops of peak performance when it’s installed later this year. “Sandia National Laboratories has been an active partner in leveraging our…

HowTos – Linux Security – HowTo Block SSH Server Attacks Using “DenyHosts”.

DenyHosts is an open source log-based intrusion prevention security program for SSH servers developed in Python. It is intended to monitor and analyzes SSH server logs for invalid login attempts, dictionary based attacks and brute force attacks by blocking the originating IP addresses by adding an entry to /etc/hosts.deny file on the server and prevents the IP address from making any further such…

Why Is Microsoft Showing So Much Interest In Linux, Apache Mesos, DC/OS and other opensource software lately?

It appears that Microsoft has decided that the operating system is no longer an important battleground, and that it’s more important to gain market share in cloud (Azure and Office 365) than it is to put energy into battling Linux for application market share. Microsoft’s cloud strategy has shifted to customer choice, including support for…

Why Unikernels Are Great for DevOps

Unikernels are application sized virtualization like a container but use a unique kernel and OS like with a virtual machine. They are an image that contains a library operating system that can be directly be run on a hypervisor. Unikernels are single-purpose virtual machines (VM). They only run one application—which is interesting when you think about it, because that’s…

How to Install Ruby on CentOS/RHEL 8 – for Peatio install

Installing Ruby from the CentOS repositories.   Peatio install series. Run the following commands as root or user with sudo privileges to install the ruby package: #sudo dnf install ruby relax and wait for the installation to compete. Once installation is completed, you can verify that it was successful by printing the Ruby version: $ruby –version…

All about RPM ( redhat Package Manager) HowTos

How can I list the contents of an uninstalled rpm To list the contents. find out what dependencies a rpm file has: $ rpm -qpR [.rpm-file] $ rpm -qR [package-name] The RPM package manager rpm comes with various utilities to interact with packages. The following command will list all the files inside an RPM package:…

This may end the likes of Facebook’s social networking giants disinformation enterprise….

To download whitepaper: Download On the lines of EU’s GDPR (General Data Protection Regulation). Regulating and decentralizing social netoworks like Facebook, Twitter, Linkedin and Youtube.  Senator Warner wants legislation that will allow social networks that have the capacity to “promote disinformation that undermines trust in our institutions, democracy, free press, and markets. You will have…

Signature of a Cyberattack

A DNS amplification attack is a reflection-based distributed denial of service (DDos)attack. The attacker spoofs look-up requests to domain name system (DNS) servers to hide the source of the exploit and direct the response to the target. … Most commonly, these are DNS servers that support open recursive relay.  DNS amplification can also be described as a Distributed Denial…

HowTos : How to log all LVM commands

By default, the LVM configuration does not allow you to log the commands that are used in a shell or in a GUI (e.g system-config-lvm) environment. However, it’s possible to active logging using the configuration file /etc/lvm/lvm.conf. Activate logging for all LVM commands To active logging follow these steps. 1. Edit the lvm.conf file and find…

HowTos – send Audit Logs to a Remote Rsyslog Server in RHEL7X

Perform these steps to set up the syslog server: 1. Uncomment the following lines in the ‘MODULES‘ section of /etc/rsyslog.conf: # vi /etc/rsyslog.conf $ModLoad imtcp $InputTCPServerRun 514 If you are using UDP then uncomment following lines: # vi /etc/rsyslog.conf $ModLoad imudp $UDPServerRun 514 2. Configure the rsyslog server to recieve rsyslog events from client. To receive…

How can I find out how much memory my Linux is using?

From a command shell, use the “concatenate” command: cat /proc/meminfo for memory usage information. You should see a line starting MemTotal:  see below.  ie: MemTotal: 15733472 or 15GB, MemFree: and MemAvailable: This is the total memory Linux thinks it has available to use.           You can also use commands free -…

Installing CentOS packages on Red Hat Enterprise Linux – HowTos.

Are you registered to the Red Hat Network (RHN)? If not, you will see messages like this when trying to use the “yum” package installer. [root@localhost ~]# yum install pidgin Loaded plugins: rhnplugin, security This system is not registered with RHN. RHN support will be disabled. Setting up Install Process No package pidgin available. Nothing to do [root@localhost ~]# Don’t…

How do you change permissions under Linux? Explain chmod?

So long as you are the system administrator or the owner of a file or directory, you can grant permission using the chmod command. Use + symbol to add permission or – symbol to deny permission, along with any of the following letters: u (user), g (group), o (others), a (all), r (read), w (write)…

Explain the OIS Seven-Layer Model – Linux Interview Questions

THE OSI SEVEN-LAYER NETWORK MODEL LINUX The Open System Interconnect (OSI) seven-layer model [OSI7498] was first specified in the early 1980s. Although neither traditional nor modern networking protocols fit neatly into this model, it has been the common framework to discuss and explain networking protocols for over 20 years. The layered model is often called…

Did my Server get hacked? Why can’t I find ifconfig or netstat on my RHEL 7.X or CentOS 7.X Server?

If you got the following. No need to panic. ( You will get the following if you did a minimal install of rhel or centOS) # ifconfig -bash:  ifconfig: command not found As early as RHEL5 and 6 ( CentOS 5 & 6 also).2009..nearly a decade. Wow!. RedHat made the decision to no longer install the…

How to reduce or shrink the size of LVM partition ? 

Below are the logical Steps to reduce size of LVM partition :  -Umount the filesystem using umount command,  -use resize2fs command , e.g resiz2fs /dev/mapper/myvg-mylv 10G  -Now use the lvreduce command , e.g lvreduce -L 10G /dev/mapper/myvg-mylv  Above Command will shrink the size & will make the filesystem size 10GB.    How to create partition from the raw disk ?  Ans: Using fdisk utility we can create partitions…

HowTo Rsync from specific Network

Allow Rsync From a Specific Network  The following rules allows rsync only from a specific network.  iptables -A INPUT -i eth0 -p tcp -s 192.168.101.0/24 –dport 873 -m state –state NEW,ESTABLISHED -j ACCEPT    iptables -A OUTPUT -o eth0 -p tcp –sport 873 -m state –state ESTABLISHED -j ACCEPT  19. Allow MySQL connection only from a specific network  If you are running MySQL, typically you don’t want…

HowTo Rsync

Synchronize Files From Local to Remote  rsync allows you to synchronize files/directories between the local and remote system.  $ rsync -avz /root/temp/ thegeekstuff@192.168.200.10:/home/thegeekstuff/temp/  Password:  building file list … done  ./  rpm/  rpm/Basenames  rpm/Conflictname    sent 15810261 bytes  received 412 bytes  2432411.23 bytes/sec  total size is 45305958  speedup is 2.87  While doing synchronization with the remote server, you need to specify username and ip-address of the remote…

HowTo Find commands in Linux

Practical Linux Find Command Examples  In this article, let us review 15 practical examples of Linux find command that will be very useful to both newbies and experts. First, create the following sample empty files under your home directory to try some of the find command examples mentioned below.  # vim create_sample_files.sh  touch MybashProgram.sh  touch mycprogram.c …

How to Linux passwordless SSH logins

Here is a short note on configuring passwordless logins between 2 Linux systems. Process basically involves generating a public authentication key and appending it to the remote hosts ~/.ssh/authorized_keys file. Generate authentication key If an SSH authentication-key file does not exist, generate one by running the ssh-keygen command. When prompted for a passphrase, use a blank passphrase…

All about systemd

systemd System and Service Manager What is this? systemd is a suite of basic building blocks for a Linux system. It provides a system and service manager that runs as PID 1 and starts the rest of the system. systemd provides aggressive parallelization capabilities, uses socket and D-Bus activation for starting services, offers on-demand starting of daemons, keeps…

HOWTo Network interface configuration in Linux

 # /etc/sysconfig/network-scripts/ifcfg-eth# The system reads the network interface files during the boot process to determine which interfaces to bring up and how to configure them. The file name format of the network interface configuration file is  /etc/sysconfig/network-scripts/ifcfg-eth#. So if you want to configure the interface eth0, the file to be edited is /etc/sysconfig/network-scripts/ifcfg-eth0. Below is…

HowTo IPSec tunnel and VPN – Diffie-Hellman

Overview of Diffie-Hellman Diffie-Hellman is an asymmetric key algorithm used for public key cryptography. As well as IPSec it is also used for SSL, SSH, PGP and other PKI systems. The Diffie-Hellman algorithm was created to address the issue of secure encrypted keys from being attacked over the internet when in transmission, though using the…

How can I speed up performance of my RH using multiple swap partitions?

If your system (especially a server) has multiple drives set up as a RAID 0 array (data striping), it would automatically spread the data across all the drives in parallel, greatly increasing the speed of disk writes versus a non-RAID setup, where the swap partition is on only one drive. Of course, not everyone can…

What are the contents of /usr/local?

It contains locally installed files. This directory matters in environments where files are stored on the network. Specifically, locally-installed files go to /usr/local/bin, /usr/local/lib, etc.). Another application of this directory is that it is used for software packages installed from source, or software not officially shipped with the distribution.

How would you reduce or shrink the size of LVM partition?

Answer: Unmount the filesystem using unmount command, Use resize2fs command , e.g resiz2fs /dev/mapper/myvg-mylv 10G Now use the lvreduce command as lvreduce -L 10G /dev/mapper/myvg-mylv The above Command will shrink the size LVM partition and fixes the filesystem size to 10GB.Most in-depth, industry-led curriculum in linux.

How can I recursively count files in a Linux directory?

How can I recursively count files in a Linux directory? I found this: find DIR_NAME -type f | wc -l or see example below: ” Found 187550 files in the directory /var/* Write a command that will do the following: -look for all files in the current and subsequent directories with an extension c,v -strip…

What does Sar provide? Where are Sar logs stored?

Sar collects, reports, or saves system activity information, sar serves to log and evaluate a variety of information regarding system activity. With performance problems, sar also permits retroactive analysis of the load values for various sub-systems (CPUs, memory, disks, interrupts, network interfaces and so forth) and limitation of problems in this manner. If CPU utilization…