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CentOS/RHEL

How to Check the Size og yum Channels in CentOS/RHEL

By admin

Question: How to find out how large a yum channel repository is, to know how much data the channel will sync to a local yum repository? To see the actual size of the repository use either the 'yum repolist -v' or 'yum repoinfo' command. Example for checking the size of "CentOS-8 - AppStream" yum channel Run the command as shown below to get the size of the Repo "CentOS-8 - AppStream". The command works even without the double quotes around the repo name. # yum repoinfo "CentOS-8 - … [Read more...] about How to Check the Size og yum Channels in CentOS/RHEL

Filed Under: CentOS/RHEL

Repairing filesystem issues at Boot in CentOS/RHEL 7 and 8

By admin

This post focuses on manually repairing the file-system configuration or corruption issues that stop the boot process. Diagnosing and fixing file system issues Errors in /etc/fstab and corrupt file systems can stop a system from booting. In most cases, systemd drops to an emergency repair shell that requires the root password. The following table lists some common errors and their results. Common File System Issues PROBLEM RESULT Corrupt file system systemd attempts to repair the … [Read more...] about Repairing filesystem issues at Boot in CentOS/RHEL 7 and 8

Filed Under: CentOS/RHEL, CentOS/RHEL 7, CentOS/RHEL 8, Linux

How to Use Udev Rules to Create oracleasm Disks in CentOS/RHEL 8

By admin

This post will help to configure Oracleasm disks using Udev rules in 2 node cluster. On first node 1. List the disks: [root@node01 ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 2G 0 disk sdb 8:16 0 2G 0 disk Note: Create partitions for the disks. 2. Find the disk ID: [root@node01 ~]# udevadm info --query=all --name=/dev/sda | egrep "WWN|SERIAL" E: ID_SCSI_SERIAL=[id] E: ID_SERIAL=0QEMU_QEMU_HARDDISK_AAAAAAAAA E: … [Read more...] about How to Use Udev Rules to Create oracleasm Disks in CentOS/RHEL 8

Filed Under: ASM, CentOS/RHEL, CentOS/RHEL 8, Linux, oracle

How to Configure an NFSv4-only Client using nfsconf in CentOS/RHEL 8

By admin

The nfsconf tool CentOS/RHEL 8 introduces the nfsconf tool to manage the NFS client and server configuration files under NFSv4 and NFSv3. Configure the nfsconf tool using /etc/nfs.conf (the /etc/sysconfig/nfs file from earlier versions of the operating system is deprecated now). Use the nfsconf tool to get, set, or unset NFS configuration parameters. The /etc/nfs.conf configuration file is composed of multiple sections starting with a key word in square brackets ([keyword]) with value … [Read more...] about How to Configure an NFSv4-only Client using nfsconf in CentOS/RHEL 8

Filed Under: CentOS/RHEL, CentOS/RHEL 8, Linux

Beginners Guide to Tuning Profiles in CentOS/RHEL

By admin

Tuning Systems System administrators can optimize the performance of a system by adjusting various device settings based on a variety of use case workloads. The tuned daemon applies tuning adjustments both statically and dynamically, using tuning profiles that reflect particular workload requirements. Configuring Static Tuning The tuned daemon applies system settings when the service starts or upon the selection of a new tuning profile. Static tuning configures predefined kernel parameters … [Read more...] about Beginners Guide to Tuning Profiles in CentOS/RHEL

Filed Under: CentOS/RHEL, CentOS/RHEL 7, CentOS/RHEL 8, Linux

Beginners Guide to Managing Package Module Streams in CentOS/RHEL 8

By admin

Introduction to Application Streams CentOS/RHEL 8.0 introduces the concept of Application Streams. Multiple versions of user-space components shipped with the distribution are now delivered at the same time. They may be updated more frequently than the core operating system packages. This provides you with greater flexibility to customize Red Hat Enterprise Linux without impacting the underlying stability of the platform or specific deployments. Traditionally, managing alternate versions of an … [Read more...] about Beginners Guide to Managing Package Module Streams in CentOS/RHEL 8

Filed Under: CentOS/RHEL, CentOS/RHEL 7, CentOS/RHEL 8, Linux

Common Error Messages from Command xfs_repair in Linux

By admin

The post explains some of the common error messages from command xfs_repair and the repairs that it performs. disconnected inode 242002, moving to lost+found xfs_repair found an inode that is in use but is not connected to the filesystem. The inode is moved to the filesystem's lost+found directory. Its name is its inode number (in this example, 242002). If the disconnected inode is a directory, the directory's subtree is preserved--all of its child inodes are automatically moved with it. So, … [Read more...] about Common Error Messages from Command xfs_repair in Linux

Filed Under: CentOS/RHEL, Linux

How to Permanently set the ethtool settings in CentOS/RHEL 6

By admin

Modifications made with the ethtool command are by default disappeared after a reboot. For permanent settings, the interface configuration file has to be edited. For each network device, there will be a file in the /etc/sysconfig/network-scripts/ For example, for device eth0 there will be /etc/sysconfig/network-scripts/ifcfg-eth0 containing the properties of the device. A line can be added to the file to automatically implement the settings allowed by the "ethtool -s" command. For example: # … [Read more...] about How to Permanently set the ethtool settings in CentOS/RHEL 6

Filed Under: CentOS/RHEL, CentOS/RHEL 6, Linux

How to Check if any of the RPM files were tampered with

By admin

Question: In some scenarios which it is suspected that the files in the system from an rpm installation, have been altered, changed, or tampered with. For example, the system was hacked and a binary file of ssh tampered with. How to check if changes were made on it comparing since the installation? To verify and check if the files installed on a system with rpm or yum altered since installation using the following command: # rpm -V [PACKAGE_NAME] If you have any of the files altered in … [Read more...] about How to Check if any of the RPM files were tampered with

Filed Under: CentOS/RHEL, Linux

How to Create a MySQL Docker Container for Testing

By admin

Docker is a container runtime environment that allows programs to operate in a jailed environment without any required external dependencies. Containers are similar in some concepts to virtual machines, however, they do not use a hypervisor and run in a single kernel instance, often sharing the instance with other containers. One of the prime features of containerization is the lack of external dependencies; the container has all of the runtime libraries and components needed to run the … [Read more...] about How to Create a MySQL Docker Container for Testing

Filed Under: CentOS/RHEL, CentOS/RHEL 6, CentOS/RHEL 7, DevOps, Docker, mysql

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