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CentOS/RHEL

sestatus Command Examples in Linux

by admin

SELinux can either be in an enabled or a disabled state. In order to check in which state it is running, we can make use of the getenforce command. There are two modes in which SELinux runs: There are two modes in which SELinux runs: Enforcing: This is the enabled state where all rules are […]

Filed Under: CentOS/RHEL, Linux

setenforce Command Examples in Linux

by admin

We can change the SELinux modes from enforcing to permissive and vice versa during runtime by using the setenforce command. Before and after changing the SELinux mode, we must ensure the current mode by using the getenforce command. SELinux can either be in an enabled or a disabled state. In order to check in which […]

Filed Under: CentOS/RHEL, Linux

Sample /etc/kdump.conf configuration file

by admin

An image of system memory captured after a kernel crash or hang is called a crash dump. Analyzing a crash dump can give valuable clues for postmortem analyses of kernel problems. However, obtaining a dump after a kernel crash is inherently unreliable because the storage driver responsible for logging data onto the dump device might […]

Filed Under: CentOS/RHEL

How to use ipset Command in Linux

by admin

IP sets are stored collections of IP addresses, network ranges, MAC addresses, port numbers, and network interface names. The iptables tool can leverage IP sets for more efficient rule matching. For example, let’s say you want to drop traffic that originates from one of several IP address ranges that you know to be malicious. Instead […]

Filed Under: CentOS/RHEL, Linux

‘error opening class fc_host’ – systool Command Error on CentOS/RHEL 7 and 8

by admin

The Problem When running the systool command on CentOS/RHEL 7, the following error message is reported: # systool -c fc_host -v Error opening class fc_host The Solution The error occurs because the scsi_transport_fc module that is responsible for populating the contents of /sys/class/fc_host/ directory is not loaded on the system. 1. Manually load the scsi_transport_fc […]

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

Dependency failed for NFS server and services

by admin

The Problem Attempting to start the NFS (nfs-server.service) on CentOS/RHEL 7 fails as follows: # systemctl status nfs-server.service nfs-server.service – NFS server and services Loaded: loaded (/usr/lib/systemd/system/nfs-server.service; enabled; vendor preset: disabled) Drop-In: /run/systemd/generator/nfs-server.service.d ‘-order-with-mounts.conf Active: inactive (dead) Mar 09 16:17:10 hostname systemd[1]: Dependency failed for NFS server and services. Mar 09 16:17:10 hostname systemd[1]: nfs-server.service: […]

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

How to Change Default Port of Apache On RHEL/CentOS 7

by admin

If you want to change Port in the Apache configuration file it’s easy to do. You can also run a website on a different port rather than the default port. 1. Let’s check which is listening to which service: # nmap -sT -O localhost 2. Check whether Port 8000 is free or not: # lsof […]

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

How to move /tmp on a separate disk as a separate mount point (Online)

by admin

By default when you install any Linux system, the /tmp directory is created automatically under the root partition(‘/’). In some situations, you might want to separate out the /tmp directory on a different mount point or partition altogether. Especially when you want to manage it independently and have a large amount of data to be […]

Filed Under: CentOS/RHEL, Linux

How to use ldconfig Command in Linux

by admin

ldconfig command is used to tell the system about new locations of shared libraries. The uses information provided by the /etc/ld.so.conf configuration file. The ldconfig command creates a cache database of all libraries based on the configuration file. This cache is normally stored in the /etc/ld.so.cache file. Here is the syntax of the ldconfig command: […]

Filed Under: CentOS/RHEL, Linux

How to Troubleshoot Performance Issues on Linux – Beginners Guide

by admin

Following is the list of OS commands apart from basic commands output that are useful in diagnosing the problems at OS end causing the slow performance to the Database or application side. 1. iotop The iotop command is top like utility for disk I/O. It watches I/O usage information output by the Linux kernel (requires […]

Filed Under: CentOS/RHEL, Fedora, Linux

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