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…
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…
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…
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…
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…
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…
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…
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:…
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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…
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…
#usermod -L user This will add an exclamation mark “!” in the second field of the file /etc/passwd. or use #passwd -l testuser There are several ways in which user account can be locked or disabled. The posts discusses few of the most widely used ways. 1. Lock the password To lock a users account…
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…
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…
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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 -…
Show Processes Sorted by any Top Output Column – Press O By default top command displays the processes in the order of CPU usage. When the top command is running, press M (upper-case) to display processes sorted by memory usage as shown below. Fig: Press M to sort by memory usage – Unix top command To…
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…
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Hard links point directly to the physical file on disk, and not on the pathname. This means that if you rename or move the original file, the link will not break since the link is for the file itself, not the path where the file is located.
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 How can I find out how much memory my Linux is using? How do you change permissions under Linux? Explain chmod? What are hard links? What are filenames that are preceded by a dot?
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…
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…
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…
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…
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…
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 …
Backup Entire Hard disk To another DISK 1. In Below example we want to clone disk “sda” and have an identical disk on the server as “sdb”. # fdisk -l Disk /dev/sda: 12.9 GB, 12884901888 bytes 255 heads, 63 sectors/track, 1566 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical):…
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…
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…
# /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…
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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…
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…
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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.
filenames that are preceded by a dot are hidden files. These files can be configuration files that hold important data or setup info. Setting these files as hidden makes it less likely to be accidentally deleted.
Any filename can have a maximum of 255 characters. This limit does not include the path name, so therefore the entire pathname and filename could well exceed 255 characters.
Write a command that will look for files with an extension “sh”, and has the occurrence of the string “apple” in it. Find ./ -name “*.sh” | xargs grep –i “apple”
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? 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…
Answer: The finger service should be disabled because a remote user can get important information about the system by using that command.
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…