Changing The Default Kernel With Grubby

Grubby tool can be used to read information and make changed to the grub.cfg file. Listing the default kernel: grubby –default-kernel /boot/vmlinuz-4.14.12-1.el7.elrepo.x86_64 To find out what the index number of the default enter the following # grubby –default-index 0 To view all the kernels enter the following command: grubby –info=ALL # grubby –info=ALL index=0 kernel=/boot/vmlinuz-4.14.12-1.el7.elrepo.x86_64 […]

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Upgrading and Installing with RPM

RPM Package Manager RPM package manager is commonly use with RHEL/CentOS based Linux Distros. The name Redhat Package Manager or RPM, refers to the files format, .rpm If you are attempting to install from a RPM file, you will need to specify with the “-i” option. If you are attempting to upgrade from a RPM […]

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Configuring SSL/TLS on Nagios

This post describes how to configure SSL/TLS on your Nagios server. During the initial setup, I’m using CentOS 7.x. yum install -y mod_ssl openssl Next, go to root’s home directory. If you are not logged in as root, go ahead and do so. cd ~ Next will need to generate a Private Key File. This […]

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Nagios Notifications Not Working

If for some reason, your Nagios server stops sending out host alerts it’s more than likely that recent update broke it. If that is the case, you will need to re-run the update, which should fix the issue. In the event that this does not fix the problem, check your email settings in nagios. This […]

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XINETD/NRPE | Cannot Write to Pidfile

 Cannot write to pidfile ‘/var/run/nagios/nrpe.pid’ – check your privileges. This error occurs when the “pidfile” cannot be rewritten. In most cases, this happens after a reboot and the file itself is read-only instead of read/write. If that is the case, go ahead and restart the xinetd and nrpe services. service xinetd restart service nrpe restart Next, check the status […]

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Install VNC-Server on CentOS 7

First, i logged into my server as root, to make things a little easier. I would recommend doing the same thing to help speed up the processes. After I logged into the system, I installed VNC-server.  yum install tigervnc-server Once all the packages were installed, go ahead and run an update. yum -y update && […]

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Enable noop IO scheduler

Noop Scheduler, for those of you who don’t know, is the simplest I/O scheduler for Linux. NOOP scheduler inserts all incoming I/O requests into a simple FIFO queue and implements request merging. In other words, the scheduler assumes that the host is unaware of how to productively re-order requests. There for, noop handles all IO scheduling. Lets enable enable noop. […]

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Slow SSH Login | UseDNS=no

Problem: When SSH’ing into a server, connection, and login take a long time. Connect to a server Attempt to log in, and wait to see how long the connection takes. 10+ seconds is too long and should be investigated. Wait for the password prompt and then proceed to  cat /etc/ssh/sshd_config | less use vi to […]

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