CentOS/RHEL 8

The Problem While executing the command "lsb_release -r" to display the release number of the currently installed distribution, user gets below error: # lsb_release -v -bash: lsb_release: command not found How this can be resolved? The Solution To check the RedHat/CentOS version one can use the “lsb_release” command. In most cases, the package providing this command is not installed by default on the systems. To check which package provides the lsb_release command use the below … [Read more...] about “lsb_release: command not found” – Fix in CentOS/RHEL

Virtual Data Optimizer (VDO) is a block virtualization technology that allows you to easily create compressed and deduplicated pools of block storage. This post outlines steps to create Virtual Data Optimizer(VD0) filesystem in CentOS/RHEL 8 systems. 1. Install VDO using dnf or yum. # dnf install install vdo Verify the package installation: # rpm -qa | grep vdo kmod-kvdo-6.2.0.293-50.0.1.el8.x86_64 vdo-6.2.0.298-10.el8_0.x86_64 2. Create a VDO disk: # lsblk | grep sdc NAME MAJ:MIN … [Read more...] about How To Create Virtual Data Optimizer(VD0) in CentOS/RHEL 7 and 8

"stratis" is the new volume manager introduced in the CentOS/RHEL 8 release. This post outlines steps to create or remove a new stratis filesystem in CentOS/RHEL 8 system. We will also see how to mount and umount a stratis filesystem in this post. Creating and mounting a stratis filesystem 1. Install Stratis packages: # rpm -qa | grep "strati*" stratisd-1.0.3-1.el8.x86_64 stratis-cli-1.0.2-1.el8.noarch 2. Enable and start the stratisd service: # systemctl enable --now stratisd # … [Read more...] about How To Create/Remove and Mount a Stratis Filesystem in CentOS/RHEL 8

What is early kdump support? In previous versions of CentOS/RHEL (5/6/7), the kdump service would start very late in the boot sequence. So early crashes information is lost during the booting. Starting CentOS/RHEL 8, a new kdump mechanism called "early kdump support" was introduced to tackle this issue. Early Kdump stores the vmlinuz and initramfs of the crash kernel inside the initramfs of the booting kernel and load them directly into the reserved memory (crashkernel) during early boot … [Read more...] about How to Configure Early-kdump Support Feature in CentOS/RHEL 8

This article explains how to bootup CentOS/RHEL 7 and 8 system into rescue mode or emergency mode. In CentOS/RHEL 7 and 8, both rescue mode and emergency mode are systemd targets which replaced the concept of runlevels in previous CentOS/RHEL versions. Rescue mode is equivalent to single user mode and requires the root password. Rescue mode allows you to repair your system in situations when it is unable to complete a regular booting process. Rescue mode will try to mount all local file … [Read more...] about How to Boot into Rescue Mode or Emergency Mode Through Systemd in CentOS/RHEL 7 and 8

In CentOS/RHEL 8 the network services scripts are not presented anymore(systemctl start network.service or /etc/init.d/network script). In order to restart the network services follow one of these two options. Using Network Manager Use the systemctl command to restart the NetworkManager service/target as shown below: # systemctl restart NetworkManager Using nmcli Tool Note: Run these commands from the GUI or the console, as the network will disable. # nmcli networking off # nmcli … [Read more...] about How to Restart Network Services in CentOS/RHEL 8

dnf has a distro-sync option which is used to synchronize installed packages to the latest available versions. It does the necessary upgrades, downgrades or keeps selected installed packages to match the latest version available from any enabled repository. If no package is given, all installed packages are considered. The distro-sync option of DNF is similar to yum's update option. The following is an example of the distro-sync option: # dnf distro-sync Last metadata expiration check: … [Read more...] about How To Use distro-sync Option With dnf To Upgrade OS (CentOS/RHEL 8)

CentOS/RHEL has a new package manager called DNF which can be used to install packages on CentOS/RHEL 8 systems. DNF or Dandified YUM is the next-generation version of the Yellowdog Updater Modified (yum), a package manager for rpm-based distributions in CentOS/RHEL 8. It also resolves dependencies automatically. The following is an example of how to use DNF to check which repositories are enabled and to then install a package from an enabled repository. 1. To check the list of … [Read more...] about How to install packages using dnf in CentOS/RHEL 8

CentOS/RHEL 8 distributes sets of related RPM packages that form a logical unit (such as different components of an application or a group of tools) as modules, with these modules being able to be enabled or disabled on the system. How can a user or administrator of an OL8 system determine what modules are installed or are enabled or disabled on their system? Modules a set of RPM packages that are grouped together and must be installed together. They can contain several streams (AppStreams) … [Read more...] about How to list all modules and check if they are enabled or disabled in CentOS/RHEL 8