Fix lỗi “Welcome to Emergency mode” trên linux

How to Install Nagios 4.4.5 on RHEL/CentOS 8/7 and Fedora 30

Nagios is an awesome Open Source monitoring tool, it provides you more comprehensive monitoring environment to always keep an eye on your all machines/networks whether you are in your data center or just your small labs.

With Nagios, you can monitor your remote hosts and their services remotely on a single window. It shows warnings and indicates if something goes wrong in your servers which eventually helps us to detect some problems before they occur. It helps us to reduce downtime and business losses.

Recently, Nagios released its latest versions Nagios Core 4.4.5 and its latest stable release of Nagios plugins 2.2.1 on August 20, 2019.

This article is intended to guide you with easy instructions on how to install the latest Nagios Core 4.4.5 from source (tarball) on RHEL 8/7/6, CentOS 8/7/6 and Fedora 26-30 distributions.

Extending partitions on Linux VMware virtual machines

This only applies to ext3 disks that use the logical volume manager.

1. Shutdown the VM

2. Right click the VM and select Edit Settings

3. Select the hard disk you would like to extend

4. On the right side, make the provisioned size as large as you need it

5. Click OK

6. Power on the VM

7. Connect to the command line of the Linux VM via the console or putty session

8. Log in as root

How to configure a static IP address on CentOS 7 / RHEL 7

On CentOS 7 or RHEL 7 one need to use the NetworkManager daemon. It attempts to make networking configuration and operation as painless and automatic as possible by managing the primary network connection and other network interfaces, like Ethernet, WiFi, and Mobile Broadband devices. In this quick tutorial you will learn about configuring a network interface using ifcfg files located in /etc/sysconfig/network-scripts/ directory in a CentOS 7 and RHEL 7:

1. Create a file named /etc/sysconfig/network-scripts/ifcfg-eth0 as follows:
2. DEVICE=eth0
3. BOOTPROTO=none
4. ONBOOT=yes
5. PREFIX=24
6. IPADDR=192.168.2.203
7. Restart network service: systemctl restart network

Configure Postfix to use Gmail as a Mail Relay

1. Install Required Software
   • Debian, Ubuntu:
   • Fedora:
   • CentOS:
   • OpenSUSE:
   • Arch Linux:
   • FreeBSD:
2. Configure Gmail Authentication
   • Debian, Ubuntu, Fedora, CentOS, OpenSUSE, Arch Linux:
   • FreeBSD:
3. Configure Postfix
   • Debian, Ubuntu, Arch Linux:
   • Fedora, CentOS:
   • OpenSUSE:
   • FreeBSD:
4. Process Password File
5. Debian, Ubuntu, Fedora, CentOS, OpenSUSE, Arch Linux:
6. FreeBSD:
7. Restart Postfix
   • Debian, Ubuntu, Fedora, CentOS, OpenSUSE, Arch Linux:
   • FreeBSD:
8. Enable “Less Secure Apps” In Gmail
9. Send A Test Email
10. Troubleshooting
    • Debian:
    • Ubuntu, Fedora, CentOS, OpenSUSE, Arch Linux:
    • FreeBSD:

Postfix for mail relay

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = mailgw.ics.com.vn
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = ipics.com.vn, mailgw.ics.com.vn, localhost.ics.com.vn, localhost
relayhost =
mynetworks = 127.0.0.0/8 ipaddress/32 ipaddress/32 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all