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
Linux
How to Configure an NFSv4-only Client using nfsconf in CentOS/RHEL 8
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
How to Schedule Tasks Using at in Linux
The atd Daemon The atd daemon allows users to submit jobs to be performed at a later time, such as "at 2:00am". In order to use the atd daemon, it must be running. Users can confirm that atd is running simply by examining a list of running processes: $ ps aux | grep atd daemon 4730 0.0 0.2 1420 532 ? S 15:42 0:00 /usr/sbin/atd madonna 5570 0.0 0.2 3572 640 pts/2 S 16:43 0:00 grep atd Notice that the seventh column specifies what terminal a process is associated … [Read more...] about How to Schedule Tasks Using at in Linux
Beginners Guide to Tuning Profiles in CentOS/RHEL
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
Beginners Guide to Managing Package Module Streams in CentOS/RHEL 8
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
Common Error Messages from Command xfs_repair in Linux
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
How to Permanently set the ethtool settings in CentOS/RHEL 6
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
How to Check if any of the RPM files were tampered with
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
How to extract RAR files in CentOS/RHEL 7 and 8
There is no default utility in CentOS/RHEL 7 systems to extract a .rar file. This post outlines the steps to install the unar package and use of unar command to extract files with .rar extension. 1. Log in as a root user (or use sudo) and configure the latest EPEL repositories to be able to install the unar package: # yum install epel-release Note: I recommend to disable all the existing repositories and just enable the EPEL repository if you do not want to face any conflict. 2, Now … [Read more...] about How to extract RAR files in CentOS/RHEL 7 and 8
What is the purpose of utmp, wtmp and btmp files in Linux
In a Linux system, everything is logged in a log file under the directory called /var/log. This directory contains logs related to different services and applications. In this directory we have some files such as utmp, wtmp and btmp. Unlike the system log files and the authentication log files, all of these files are binary files. So, we can't use our normal text tools, such as less or grep, to read them or extract information from them. Instead, we'll use some special tools that can read these … [Read more...] about What is the purpose of utmp, wtmp and btmp files in Linux