In this tutorial, we will discuss how to integrate Linux Servers(Centos/RHEL) with Windows Active Directory for authentication purposes. In my case, I have Centos/RHEL 6 servers. Follow the below steps to integrate these servers with AD using samba, winbind, and Kerberos. Step 1: Install the samba-winbind and kerberos packages. # yum install samba-winbind samba-winbind-clients samba […]
CentOS/RHEL 6
Zenoss Core Installation & Configuration on CentOS/RHEL 6.X
Zenoss is an open-source real-time monitoring tool and comes under GNU General Public License (GPL) version 2. It provides a web interface that allows system administrators to monitor availability, inventory/configuration, performance, and other events. Most Common Features: Application, Network and Systems Monitoring and Management Alerting and Automatic Remediation System Log Monitoring and Event Management Automated […]
Set Password for Single User Mode on Linux (CentOS/RHEL)
Setting Password for Single User Mode in Linux adds security to Linux boxes. If someone accesses your server physically & reboots the server and then tries to change the root password from single-user mode. In that case, if the password is set on single-user mode, one has to first enter the root password, then only […]
Spacewalk Installation Steps On CentOS/RHEL
Spacewalk is an open-source configuration management tool sponsored by Red Hat. Spacewalk is an alternate of the Redhat network satellite server on Centos/Fedora/Scientific Linux. Spacewalk is the upstream project for the source of the Red Hat Network Satellite. It provides a management interface for software content across registered servers. Some of important Features of Spacewalk […]
Couldn’t find device with uuid [UUID] – LVM Not Active on Reboot
The Problem After a reboot the system will not start or activate one of the LVM volume groups. Trying to activate the group manually produces the message: Couldn’t find device with uuid ‘[UUID]’ The Solution The string LABELONE at the metadata location marks the device as being part of an LVM device. Without this string, […]
“VFS: Cannot open root device “UUID=[UUID]” or unknown-block(0,0)” – Booting issue CentOS/RHEL/OEL 6
The Problem Server fails to boot with latest kernel with the below errors from console logs: Initializing network drop monitor service md: Waiting for all devices to be available before autodetect md: If you don’t use raid, use raid=noautodetect md: Autodetecting RAID arrays. md: Scanned 0 and added 0 devices. md: autorun … md: … […]
How to Find the Original Installation OS Version in CentOS/RHEL
This post explains how to find the OS version which was first installed on a CentOS/RHEL system. CentOS/RHEL 6 Run grep -m1 “label =” /var/log/anaconda.storage.log to find the original installation OS version. Current version: # cat /etc/redhat-release CentOS Linux release 6.10 Original installation version: # grep -m1 “label =” /var/log/anaconda.storage.log label = EL6.8_x86_64_Disc_1_20160518 size = […]
How To Calculate The Memory Reserved By HugePages in CentOS/RHEL
Question: How to Calculate the percentage of memory reserved by Huge Pages? 1. Inspect the memory parameters: # cat /proc/meminfo MemTotal: 98721456 kB MemFree: 1277612 kB MemAvailable: 12186676 kB Buffers: 20496 kB Cached: 11013124 kB SwapCached: 4820 kB Active: 2303780 kB Inactive: 9716992 kB Active(anon): 716672 kB Inactive(anon): 582092 kB Active(file): 1587108 kB Inactive(file): 9134900 […]
How To Configure NIS (Network Information System) Master and Slave Servers in CentOS/RHEL
The Network Information Service consists of a client-server directory service protocol for distributing system configuration data such as user and host names between computers. NIS enables you to create user accounts that can be shared across all systems on your network. The description of NIS daemons are given below: portmap/rpcbind: The foundation RPC daemon upon […]
How To Disable Weak Cipher And Insecure HMAC Algorithms in SSH services for CentOS/RHEL 6 and 7
This post will show how to Disable the HMAC MD5 and the CBC ciphers as an example for CentOS/RHEL 6 and 7. For CentOS/RHEL 7 For more information please look at the man pages: # man sshd_config Ciphers Specifies the ciphers allowed. Multiple ciphers must be comma-separated. If the specified value begins with a ‘+’ […]