Redhat / CentOS / AlmaLinux

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.

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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

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If you currently do not hold a Red Hat Subscription and yet you need to enable EPEL ( Extra Packages for Enterprise Linux ) repository on your RHEL 7 Linux you need to download and install following file directly from Fedora project:

epel-release-7-5.noarch.rpm

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There are number of ways how to find you what Redhat Linux version is my server running on. First check /etc/os-release file:

# cat /etc/os-release 
NAME="Red Hat Enterprise Linux Server"
VERSION="7.0 (Maipo)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="7.0"
PRETTY_NAME="Red Hat Enterprise Linux Server 7.0 (Maipo)"

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In this config we are going to configure a network interface to receive an IP configuration settings from DHCP server. First get the name of the network interface you would like to set as DHCP client. To do this you can run command:

# ip addr show
2: enp0s3:  mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:15:38:b7 brd ff:ff:ff:ff:ff:ff
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:fe15:38b7/64 scope link 
       valid_lft forever preferred_lft forever

Once we have located a name of the network interface in question open a corresponding configuration file. So as an example, for network interface epn0s3 vi will edit a /etc/sysconfig/network-scripts/ifcfg-enp0s3. Open this file and enter the minimum configuration settings in order to make this network interface act as a DHCP client:

DEVICE=enp0s3
BOOTPROTO=dhcp
ONBOOT=yes

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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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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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