Redhat / CentOS / AlmaLinux

Instead of changing a hostname on your Redhat 7 server manually by editing /etc/hostname you may preferably use a dedicated command hostnamectl to do this job. By default when no other options are supplied the hostnamectl command will display basic information including static hostname:

[root@rhel7 ~]# hostnamectl 
   Static hostname: rhel7
         Icon name: computer
           Chassis: n/a
        Machine ID: 75387b56d72b44b380810499805ec28a
           Boot ID: 6ad251d0e12a10e3af1894eae5fe5cb6
    Virtualization: oracle
  Operating System: Red Hat Enterprise Linux Server 7.0 (Maipo)
       CPE OS Name: cpe:/o:redhat:enterprise_linux:7.0:GA:server
            Kernel: Linux 3.10.0-123.el7.x86_64
      Architecture: x86_64

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The following linux command will list all available locales currently available on the Redhat 7 system:

[root@rhel7 ~]# localectl list-locales

The list of all available locales on your system my be quite long so use grep command to narrow down your search. Bellow command will display for example all German available locales:

[root@rhel7 ~]# localectl list-locales | grep ^de
de_AT
de_AT.iso88591
de_AT.iso885915@euro
de_AT.utf8
de_AT@euro
de_BE
de_BE.iso88591
de_BE.iso885915@euro
de_BE.utf8
de_BE@euro
de_CH
de_CH.iso88591
de_CH.utf8
de_DE
de_DE.iso88591
de_DE.iso885915@euro
de_DE.utf8
de_DE@euro
de_LU
de_LU.iso88591
de_LU.iso885915@euro
de_LU.utf8
de_LU@euro
deutsch

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Use localectl to see your currently active locale on Redhat 7 Linux. For example:

[root@rhel7 ~]# localectl
   System Locale: LANG=en_AU.UTF-8
       VC Keymap: us
      X11 Layout: us

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Changing a timezone on Redhat 7 Linux server is a easy task which can be done on a command line with a few commands. First find your timezone using timedatectl command. The following linux command will list all timezones:

[root@rhel7 ~]# timedatectl list-timezones

To narrow down the search you can use grep to search for a specific city. For example:

[root@rhel7 ~]# timedatectl list-timezones | grep -i bratislava
Europe/Bratislava

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When not using NTP you may need to set your system time manually. You have two options to set time and date on your RHEL7 linux. First option is to use date command to do this job or engage dedicated systemd timedatectl command. By default and without any arguments timedatectl will display a current time, local, universal and RTC times:

[root@rhel7 ~]# localectl
   System Locale: LANG=en_AU.iso88591
       VC Keymap: us
      X11 Layout: us
[root@rhel7 ~]# timedatectl
      Local time: Thu 2014-09-04 18:30:11 WST
  Universal time: Thu 2014-09-04 10:30:11 UTC
        RTC time: Thu 2014-09-04 10:30:10
        Timezone: Australia/Perth (WST, +0800)
     NTP enabled: n/a
NTP synchronized: no
 RTC in local TZ: no
      DST active: n/a

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I would like to know how to check gnome desktop manager version on my Redhat 7 Linux server/desktop?

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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

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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"

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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

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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.

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