I would like to know how to check gnome desktop manager version on my Redhat 7 Linux server/desktop?
Redhat / CentOS / AlmaLinux
Sync an accurate time using ntpdate on RHEL7 Linux server
To sync a correct time on your Redhat server with a NTP publicly available time servers first you need to install ntpdate
package:
[root@rhel7 ~]# yum install ntpdate
To check your current time use date
command:
[root@rhel7 ~]# date Thu Sep 4 17:20:42 WST 2014
Next, we can use pool.ntp.org
timeserver to synchronize our time. This is be done with ntpdate
command:
[root@rhel7 ~]# ntpdate pool.ntp.org 11 Dec 06:08:13 ntpdate[2225]: step time server 173.230.144.109 offset 8426822.014383 sec
Configure firewall to enable NTP port 123 on RHEL7 Linux
Once you configure NTPD service on your RHEL7 linux you will need to allow traffic through the firewall on port 123. Te following linux command will enable all public traffic on UDP port 123:
# firewall-cmd --zone=public --add-port=123/udp --permanent success
Update GRUB2 menu timeout on RHEL 7 Linux
The default settings for the GRUB2 timeout menu selection during the system boot is 5 seconds. To change this value open /etc/default/grub
grub default config file. The content of the file looks similar the the one shown below:
GRUB_TIMEOUT=5 GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)" GRUB_DEFAULT=saved GRUB_DISABLE_SUBMENU=true GRUB_TERMINAL_OUTPUT="console" GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/root crashkernel=auto \ rd.lvm.lv=rhel/swap vconsole.font=latarcyrheb-sun16 vconsole.keymap=us rhgb quiet" GRUB_DISABLE_RECOVERY="true"
Persistent/Automatic after reboot kernel module loading on CentOS/Redhat Linux
This config will describe a procedure on how to persistently load kernel modules during a boot time on CentOS or Redhat Linux system. In the below commands will use nf_conntrack_pptp
as a sample module. Replace the name of this module with a module name you wish to load.
First, create a script within /etc/sysconfig/modules/
directory with a file extension modules
. Where the name of the script can be any name of your choice. In our case the script will be called nf_conntrack_pptp.modules
. Enter a following code into your new nf_conntrack_pptp.modules
script while replacing the name of the module with the one you wish to load:
#!/bin/sh exec /sbin/modprobe nf_conntrack_pptp >/dev/null 2>&1
Failed to issue method call: Unit .service failed to load – RHEL7 Linux error
Symptom
When trying to start a service with service
or systemctl
commands on the Redhat 7 Linux system the following error message can appear on the screen:
Failed to issue method call: Unit service_name.service failed to load: No such file or directory.
Chrome Browser installation on REDHAT Linux Server/Desktop
Chrome browser is not a part of standard Redhat repositories and therefore its installation needs to be performed using external package provided by Google Inc. First download chrome browser package:
[rhel7@rhel7 ~]$ wget https://dl.google.com/linux/direct/google-chrome-stable_current_x86_64.rpm
How to display an additional package information using yum and yumdb – RedHat Linux
There are two handy tools to help you provide an additional information about system packages. The first tool is the package manager yum
and the second is yumdb
. Both tools display a different type of information. The other difference is that yumdb
command can be only used on packages currently installed on the system.
Installation of Memtest+ RAM memory test tool on Redhat 7 Linux
Installation of Memtest+ RAM memory test tool on Redhat 7 Linux
Memtest is a quite handy tool when troubleshooting hardware problem and specifically problems related to Random Access Memory (RAM). After installation the memtest+ tool will become available among other boot options. To install memtest+
on RHEL 7 Linux server execute the following linux command:
# yum install memtest86+ ... Running transaction Installing : memtest86+-4.20-12.el7.x86_64 1/1 Verifying : memtest86+-4.20-12.el7.x86_64 1/1 Installed: memtest86+.x86_64 0:4.20-12.el7
How to monitor a CPU temperature on Redhat 7 Linux system
Here is a short config to show you how to display and monitor CPU temperature on a Linux system running Redhat 7 Linux. First we need to install lm_sensors
:
# yum install lm_sensors
Next, use sensors
command to display CPU temperature:
$ sensors | grep Core Core 0: +43.0°C (high = +86.0°C, crit = +100.0°C) Core 1: +43.0°C (high = +86.0°C, crit = +100.0°C)
How to install, manage, start and autostart ssh service on RHEL 7 Linux
systemctl
command is used on RedHat 7 linux to manage services system wide. It allows administrators to manage ssh service to start, restart, stop or enable autoload after system startup.
In install ssh service on your RHEL 7 linux run a following linux command:
# yum install openssh
By defalt SSH service or to be more precise sshd
( daemon ) is disabled. Once the opensshd package installed, you can check the status of SSHD service by using the below command:
# systemctl status sshd sshd.service - OpenSSH server daemon Loaded: loaded (/usr/lib/systemd/system/sshd.service; disabled) Active: inactive (dead)
To start ssh daemon (sshd) on RHEL 7 run:
systemctl start sshd
How to reset the root password in RHEL7/CentOS7/Scientific Linux 7- based systems
Objective
Resetting the root password in RHEL7/CentOS7/Scientific Linux 7
Requirements
RHEL7 / CentOS7 / Scientific Linux 7
Difficulty
MODERATE
Instructions
Things have changed in the RHEL7 world and so has the preferred way of resetting the root password. Although the old way of interrupting the boot process (init=/bin/bash) still works, it is no longer bulletproof and recommended.
‘Systemd’ uses ‘rd.break’ to interrupt the boot. Let’s have a quick walk through the whole procedure.