Install and Configure DHCP Server on CentOS 7 / RHEL 7

DHCP (Dynamic Host Configuration Protocol) is a network protocol used for dynamically assigning IP addresses for computers attached to the network. Standard port used for DHCP service: 67(UDP).

In this tutorial we will launch dhcp server on CentOS 7 / RHEL 7 and define example subnets.
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How To Reset Forgotten Root Password on RedHat 7 / CentOS 7

RedHat 7 / CentOS 7 unlike previous version 6, doesn’t provide the ability to reset / recover root password in signle-user mode any more. This situation takes place, because RedHat 7 / CentOS 7 uses systemd manager instead of sysVinit / upstart and both systemd targets: rescue.target and emergency.target require root password. That’s why in RedHat 7 / CentOS 7 we need installation disk to boot from.
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How To Reset Forgotten Root Password on RedHat 6 / CentOS 6

RedHat 6 / CentOS 6 system gives us the opportunity to reset root password in case we forget it, on condition that we have a direct access to the machine on which we want to reset root password. Password can be reset after booting the system into single-user mode.

Steps:

1. Reboot the system

2. At the screen: “Booting Red Hat Enterprise Linux…” or “Booting CentOS…” press any key to display GRUB menu.
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LDAP Installation on CentOS 7 / RHEL 7

LDAP stands for Lightweight Directory Access Protocol. As the name suggests, it is a lightweight protocol for accessing directory services, specifically X.500-based directory services. OpenLDAP is a free, open source implementation of the Lightweight Directory Access Protocol (LDAP) developed by the OpenLDAP Project. It is released under its own BSD-style license called the OpenLDAP Public License.

In this tutorial we will show you, how to install OpenLDAP server on CentOS 7 / RHEL 7 and create basic configuration in a few simple steps:
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vsftpd installation on CentOS 7 / RedHat 7 with selinux

vsftpd (Very Secure File Transfer Protocol Daemon) is lightweight, fast and default FTP server daemon for rpm-based Linux distributions (CentOS/RHEL/Fedora).

We will install vsftpd on CentOS7 with selinux enabled in Enforcing mode.
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Detect SSH Brute Force Attack and Locate Attacker

Brute Force Attack consists of systematically checking all possible passwords until the correct one is found. If the host is exposed directly to the Internet (WAN) and SSH service is running on the host, it becomes a subject of constant brute force attacks performed by automated scripts like hydra.

To detect SSH brute force attempts on systems running systemd service manager (CentOS7/Fedora21/RHEL7), you can use journalctl command with parameters:
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