How to Install CentOS 7?

Step 1: Begin Installation

First of all, you have to download a CentOS image from the download section of the project website. Then, make a USB bootable and then restart the computer.

To begin installation, click on the Install to Hard Drive icon on the desktop.

Step 2: Select Language And Keyboard

Select your preferred language as well as the Keyboard type you have.

Step 3: Change The Installation Destination

By default, the Anaconda installer will choose automatic partitioning for your hard disk. Click on the Installation Destination icon to change this to custom partitioning.

Click on the hard drive you want to install CentOS 7 and under the Other Storage Options, choose I will configure partitioning then click Done.

Step 4: Select The Partitioning Scheme

Next, select the partitioning scheme to use for the mount points.

After that, accept the changes to apply them.

Step 5: Set Date And Time

Click on the clock icon under the localization menu and select a time zone from the map of the world, then click Done.

Once you have chosen the time and date as well as the timezone, you will see a summary of the installation. This is a good time to review all changes carefully.

Step 6: Begin Installation

Now after configuring the System and Localization settings you can click on the Begin Installation button.

The installation will begin immediately and as it proceeds you need to set up a User account as well as the root password.

Click on the root password option and enter a password and confirmation of the same then click Done. I recommend that you use a strong password to prevent it from being stolen or guessed by others.

The next step is to create a user account. Enter the correct details and if this is the administrator account, tick Make this user administrator and Require a password to use this account for security purposes.

After that, the process will continue.

Then, the installer should complete installing the software and the bootloader.

Once complete you should get a success message, after which you can click quit.

Finally, once you log in to your CentOS 7 accept the EULA agreement and enjoy!

Conclusion

Generally speaking, it is fair to say that CentOS 7 servers are very well cataloged. But it has been very well carved fame based on stability, robustness and a powerful community that document and provide help to the user of this Linux distribution.

We hope this post has been helpful to you, so share through social networks.

The post How to Install CentOS 7 Step by Step (with Pictures) appeared first on Linux Windows and android Tutorials.

Prerequisites

You must login on the server as root user or superuser privileges.
A LAMP stack required. Follow this article if you want to install it: Install LAMP in CentOS 7 and RHEL7

Install Dependencies

yum install gcc glibc glibc-common gd gd-devel make net-snmp openssl-devel xinetd unzip -y

Create Nagios User and Group

you must create a user and group for Nagios process. Create a “nagios” user and “nagcmd” group, then add the user to the group with these commands:

useradd nagios
groupadd nagcmd
usermod -a -G nagcmd nagios

Install Nagios Core

Download the latest stable release of Nagios Core from the given link copy nagios core link address and download it to your server.

Donwload Nagios Core using command wget

cd 
wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.3.tar.gz

Extract archive and switch to Nagios directory

tar -xvf nagios-4.4.3.tar.gz
cd nagios-4.4.3

Configure Nagios Script using below command

./configure --with-command-group=nagcmd
make all

Now run following commands to install Nagios, init scripts, and sample configuration files

make install
make install-commandmode
make install-init
make install-config
make install-webconf
make install-daemoninit

If you want to issue external commands from web interface to Nagios, you need to add the web server user “apache” to “nagcmd” group

usermod -G nagcmd apache

Now create nagios user “nagiosadmin” and restart the apache services.

htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

These login details will be used to access the Nagios web interface.

Install Nagios Plugins

Download the latest stable release of Nagios Plugin from the given link copy nagios plugin link address and download it to your server.

Donwload Nagios plugin using command wget

cd 
wget http://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz

Extract archive and switch to Nagios Plugin directory

tar -xvf nagios-plugins-2.2.1.tar.gz
cd nagios-plugins-2.2.1

Configure Nagios Plugin Script using below command

./configure --with-nagios-user=nagios --with-nagios-group=nagios --with-openssl

Now compile Nagios Plugins

make

Now Install Nagios Plugin

make install

Install NRPE

Use following commands

cd
wget http://downloads.sourceforge.net/project/nagios/nrpe-2.x/nrpe-2.15/nrpe-2.15.tar.gz

Extract NRPE archive and switch to NRPE directory

tar xvf nrpe-2.15.tar.gz
cd nrpe-2.15

Configure NRPE

./configure --enable-command-args --with-nagios-user=nagios --with-nagios-group=nagios --with-ssl=/usr/bin/openssl --with-ssl-lib=/usr/lib/x86_64-linux-gnu

Now compile and install NRPE

make all
make install
make install-xinetd
make install-daemon-config

Add your server IP address in xinetd startup script

vi /etc/xinetd.d/nrpe

Modify the only_from line and add the IP address of the your Nagios server to the end, in my case it is 192.168.130.138

only_from = 127.0.0.1 192.168.130.138

Save and exit.

Only Nagios server’s IP must be allowed to communicate with NRPE.

Now restart xinetd service to start NRPE

systemctl restart xinetd

Now Nagios Server is installed and we need to configure it.

Configure Nagios

Create the directory which will store the configuration file for each server that will monitor be monitor by Nagios.

mkdir /usr/local/nagios/etc/servers

Now open the main Nagios configuration file

vi /usr/local/nagios/etc/nagios.cfg

Then add below line

cfg_dir=/usr/local/nagios/etc/servers

save and exit

Configure Nagios Contacts

If you want, you can also configure nagios contacts as per your requirements using below command

vi /usr/local/nagios/etc/objects/contacts.cfg

Add a new NRPE command to our Nagios configuration

vi /usr/local/nagios/etc/objects/commands.cfg

Add the following lines at the end of the file:

define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}

Save and exit.

Now you will be able to use check_nrpe command in Nagios service definitions.

Nagios is ready to use, Lets restart the services and add them to start on server boot.

systemctl daemon-reload
systemctl restart httpd.service
systemctl start nagios.service
systemctl enable nagios.service

Access Nagios Web Interface

Open your web browser and browse below link to login your Nagios server. You must enter the login credentials that you created earlier. We will use the username “nagiosadmin”

http://nagios_server_ip/nagios

Now you will see default Nagios home page. Under “current Status” left navigation bar Click on the “Hosts” option, to see hosts which are monitoring by the Nagios.

Here you can see Nagios is monitoring only “localhost” it means itself.

Monitor a CentOS 7 Host with NRPE

In this section you will learn that how to add a new host to Nagios server, so it will be monitored. You need to repeat this section for each CentOS or RHEL server you want to monitor.

Login to the server you want to monitor and install the EPEL repository

yum install epel-release -y

Then install Nagios Plugins and NRPE:

yum install nrpe nagios-plugins-all -y

Now modify NRPE configuration file

vi /etc/nagios/nrpe.cfg

Find the line allowed_hosts and add the IP address of your Nagios server, In my case Nagios server address is 192.168.130.138

allowed_hosts=127.0.0.1,::1,192.168.130.138

Save and exit.

this configuration will accept requests from your Nagios server

Now Restart NRPE to apply changes

systemctl start nrpe.service
systemctl enable nrpe.service

All configurations done on host machine, Now we have to add these hosts to Nagios server configuration so it can start monitoring them.

Add Host to Nagios Configuration

On your Nagios server, create a new configuration file for each remote host that you want to monitor in /usr/local/nagios/etc/servers/ direcotry. I will create host1.cfg file for my fisrt host.

vi /usr/local/nagios/etc/servers/host1.cfg

Add the following host definition in host file, replace the host_name value with your remote hostname (In my case it is host1), the alias value with a description of the host, and the address value with the IP address of the remote host (My host1 address is 192.168.130.222)

define host {
use linux-server
host_name host1
alias Apache server host1
address 192.168.130.222
max_check_attempts 5
check_period 24x7
notification_interval 30
notification_period 24x7
}

With above configurations, nagios will only monitor if the host is up or down.

save and exit

Now restart Nagios server to apply new changes.

systemctl reload nagios.service

Once done, access your Nagios web interface go to Under “current Status” left navigation bar Click on the “Hosts” option, and check all hosts which are monitoring by the Nagios. now you will see that host1 is showing up there.

The post How to Install Nagios Server and Monitor your Hosts on CentOS 7 appeared first on Linux Windows and android Tutorials.

Pacemaker is an open source cluster manager software that achieves maximum high availability of your services.

Corosync Cluster Engine is an open source project derived from the OpenAIS project under new BSD License. It’s a group communication system with additional features for implementing High Availability within applications.

Prerequisites

1. Two or more CentOS Servers
2. Each server must have unique IP address
3. At leat one Floating IP Address
4. Root Privileges

Our Working Environment
host1 192.168.130.141
host2 192.168.130.142
host3 192.168.130.143
Floating IP Address 192.168.130.222

Run step 1 to step 3 on all servers host1, host2 and host3

Step 1: Configure Host File

Edit the host file on each server in order to map the hostname of all servers. login to each server (host1, host2 and host3) one by one and run below commands.

vi /etc/hosts

and add below configurations.

192.168.130.141 host1
192.168.130.142 host2
192.168.130.141 host3

Save changes and exit

Now test the hosts’ configuration using below commands.

ping -c 2 host1
ping -c 2 host2
ping -c 2 host3

Make sure ‘host1’, ‘host2’ and ‘host3’ are mapped to correct IP addresses.

Step 2: Install Nginx

Run below commands on host1, host2 and host3 to install nginx web server.

yum install epel-release -y
yum install nginx -y

After installation, set the default index.html page on each server.

##Run below Command on host1
echo '<h1>host1 - osradar.com</h1>' > /usr/share/nginx/html/index.html

##Run below Command on host2
echo '<h1>host2 - osradar.com</h1>' > /usr/share/nginx/html/index.html

##Run below Command on host3
echo '<h1>host3 - osradar.com</h1>' > /usr/share/nginx/html/index.html

Step 3: Installation and configuration of Pacemaker, Corosync, and Pcsd

Run below commands on each server to install Pacemaker, Corosync, and Pcsd

yum install corosync pacemaker pcs -y

Then run below commands on each server to enable all services to launch automatically at system boot.

systemctl enable pacemaker
systemctl enable corosync
systemctl enable pcsd

Now start the pcsd Pacemaker command line interface on all servers.

systemctl start pcsd

Now set a new password for ‘hacluster’ user password must be same for all servers. This user has been created automatically during software installation.

RUn below command to all servers and set same password.

passwd hacluster

High Availability software have been installed on to the system.

Step 4: Create and Configure Cluster

Note: Run steps 4 to step 7 on “host1” only.

We will create a new cluster with 3 servers.

we need to authorize all servers to create new cluster using below command. username will be “hacluster”

pcs cluster auth host1 host2 host3

Now create the cluster named osradar_cluster for all servers using below command.

pcs cluster setup --name osradar_cluster host1 host2 host3

Now start and enable all cluster services using below command.

pcs cluster start --all
pcs cluster enable --all

Now verify the cluster status.

pcs status cluster

Step 5: Disable STONITH and Ignore the Quorum Policy

Since we are running three node cluster and don’t have a fencing device. So we have to disable the STONITH setting but it is not recommended for production environment.

Disable STONITH and ignore Quorum policy using below commands.

pcs property set stonith-enabled=false
pcs property set no-quorum-policy=ignore

Then make sure stonith and the quorum policy are disabled.

pcs property list

Step 6: Add the Floating IP and Resources

Floating IP is the IP address that wil be migrated/moved automatically from one server to another server. Our floating ip address wil be 192.168.130.222 then we will add two resources, the Floating IP address resource with the name ‘virtual_ip’ and a new resource for the Nginx web server named ‘webserver’

Run below command to add floating IP address ‘virtual_ip’

pcs resource create virtual_ip ocf:heartbeat:IPaddr2 ip=192.168.130.222 cidr_netmask=32 op monitor interval=30s

Then run below command to add a new resource for the Nginx ‘webserver’

pcs resource create webserver ocf:heartbeat:nginx configfile=/etc/nginx/nginx.conf op monitor timeout="5s" interval="5s"

Now verify resources status and check that there is no error.

pcs status resources

Step 7: Add Constraint Rules to the Cluster

Now will configure High Availability Rules and resource constraint.

Set the collation constraint for webserver and virtual_ip resources with the score ‘INFINITY’ using below command.

pcs constraint colocation add webserver virtual_ip INFINITY

Now Set the ‘virtual_ip’ and ‘webserver’ resources always on same node servers using below command.

pcs constraint order virtual_ip then webserver

Next, stop and start the cluster

pcs cluster stop --all
pcs cluster start --all

Now again verify resources status.

pcs status resources

You can sse that virtual_ip and webserver resources started on the same server/node ‘host2’

Step 8: Configure Firewalld

Run below commands to add necessary services in firewalld.

firewall-cmd --add-service=high-availability --permanent 
firewall-cmd --add-service=http --permanent 
firewall-cmd --add-service=https --permanent

Now reload the firewalld

firewall-cmd --reload

Step 9: Testing

In this step, we will Test the node status, corosync members and status and then test the high-availability of the Nginx webserver by accessing the Floating IP address.

Test node status corosync members and corosync status using below command.

pcs status nodes
corosync-cmapctl | grep members
pcs status corosync

Finally, check the webserver High Availability. Open your web browser and type the Floating IP address 192.168.130.222

You will see the web page from the ‘host2’ server.

Now, stop the cluster on the ‘host2’ server using below command.

pcs cluster stop host2 --force

And check again the page and this time, you will see the page from the ‘host1’ server as below.

You have installed Nginx webserver High Availability with Pacemaker, Corosync, and Pcsd on CentOS 7 server successfully.

The post Create Nginx High Availability with Pacemaker and Corosync on CentOS 7 appeared first on Linux Windows and android Tutorials.

On this article, I will stick to CentOS7 system and as well following applications to work on the goal;

• hostapd => a daemon that will control how these wireless protocols should behave
• dhcpd => a daemon that taking care of handing over IP address allocation for external clients
• FirewallD => the native firewall daemon on Centos7 platforms that helps to perform NAT functionality while client internet requests traverse via wireless AP.
• I also assume that the system that we are gonna build our Access Point has wireless NIC plus another medium of access to reach the internet, for example, having a wired NIC with ISP connectivity.

01. Finding out whether your wireless nic support access-point mode:

iw list

02. Second, let make sure no blocking behavior occured on our selected wireless NIC.

rfkill list

As in the figure, both Soft & Hard blocked should say “no”, otherwise, the system won’t allow Hostapd to setup wireless on top of the selected NIC. If unfortunately blocked are in “yes”, you can work on following command to mark them as “no”

rfkill unblock wlan

03. Let install “epel-release” package which will then setup a new repository that hosts this “hostapd” package.

yum -y install epel-release

yum install hostapd dhcp

04. Once the installation completes, let’s move to hostapd specific configuration => /etc/hostapd/hostapd.conf

ctrl_interface=/var/run/hostapd
ctrl_interface_group=wheel
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
driver=nl80211

wpa=2
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

wpa_passphrase=yourpassword
interface=wlp01
bridge=br-AP
hw_mode=g
channel=6
ssid=CentOSAir

interface => on which interface that setup this wireless access point
bridge => a virtual “type => bridge” interface that manage the IP address space for the hosting access point
ssid => the name that client see as your wireless AP

05. Next step should be implement a “br-AP” virtual bridge interface that we defined while configuring hostapd.

nmcli con add con-name br-AP type bridge ifname br-AP autoconnect yes stp no ip4 192.168.10.1/24

06. To let handing over IP address leases over to clients, DHCP is a must => /etc/dhcpd/dhcpd.conf

option domain-name-servers 192.168.5.49;
default-lease-time 600;
max-lease-time 7200;
#
# this DHCP server to be declared valid
authoritative;
#
# specify network address and subnet mask
subnet 192.168.10.0 netmask 255.255.255.0 {
       range dynamic-bootp 192.168.10.200 192.168.10.220;
       option broadcast-address 192.168.10.255;
       option domain-name-servers 192.168.10.1;
       option domain-name "example.org";
       option routers 192.168.10.1;
       }

Note that IP address range should be same on both Bridge interface as well as IP address pool managed by DHCP.

07. While Linux system boots up and yet wireless NIC might not initialized as required. In such cases you might experience a service failure on “hostapd.service”. Then the tick should ask the respective initialization unit file to restart the fail service, if found. To do this, you might need to reflect default hostapd.service file to the following context => vim /etc/systemd/system/hostapd.service

[Unit]
Description=Hostapd IEEE 802.11 AP, IEEE 802.1X/WPA/WPA2/EAP/RADIUS Authenticator
After=network.target

[Service]
Type=forking
PIDFile=/run/hostapd.pid
ExecStart=/usr/sbin/hostapd /etc/hostapd/hostapd.conf -P /run/hostapd.pid -B
Restart=on-failure
RestartSec=10

[Install]
WantedBy=multi-user.target

Note following key parameters:
Restart=on-failure
RestartSec=10

08. Further, I even personally experience a failure in DHCP initialization due to early forking while our Bridge interface hasn’t completed it’s own initialization. This is a must because DHCP strictly looking for a system IP address for which it’s pool of address defined in its configuration. So, lets implement another trick by creating a systemD timer and ask it to fork the dhcpd.service with a bit of delay => vim /etc/systemd/system/dhcpd.timer

[Unit]
Description=make dhcp starts after 60sec of boot

[Timer]
OnBootSec=1min
Unit=dhcpd.service

[Install]
WantedBy=multi-user.target

What this unit does is that, even the main service of “dhcpd.service” is in disable mode at startup, this force the initialization of the dhcpd process after 60 seconds of delay.

09. Finally, reload the systemD unit files, stop DHCP service at boot process and finally start DHCP timer as well as hostapd daemon.

systemctl daemon-reload
systemctl disable dhcpd.service
systemctl enable dhcpd.timer
systemctl enable hostapd.service

10. Reboot the system and after 1 minutes of delay, check the status of;

systemctl status hostapd.service
systemctl status dhcpd.service

If they are running, then well done, you done it. But, if unfortunately a failure in hostapd.service, try to restart it again by first, disabling WIFI from NetworkManager.

nmcli radio wifi off

11. When external client traffic moving out on via our system’s public interface(or the NIC which holding your ISP connection), they should subjected to a NAT functionality, otherwise these outgoing traffic  would simply never be route back to our system to complete its communication. To setup the NAT process, lets configure firewallD.

firewall-cmd --zone=public --add-masquerade --permanent
firewall-cmd --zone=public --add-masquerade
firewall-cmd --zone=public --add-port=80/tcp
firewall-cmd --zone=public --add-port=443/tcp
firewall-cmd --zone=public --add-service=dns

Be mindful to add more rules, if required, to allow certain outgoing tcp/udp protocols.

“I hope this has been informative for you”

The post Building your own Wireless Access Point on top of CentOS7 appeared first on Linux Windows and android Tutorials.

In this article you will learn how to install CWP on your CentOS server.

CentOS Web Panel Features:

• Apache Web Server.
• PHP Selector.
• MySQL/MariaDB + phpMyAdmin.
• Email – Postfix and Dovecot, mailboxes, RoundCube web interface, SpamAssassin.
• CSF (Config Server Firewall).
• ClamAV Antivirus
• Backup Manager.
• 3rd Party Aplications.
• Easy user management interface.
• Setup Server for Web Hosting.
• DNS Server.
• Live Monitoring.
• File System Lock (means, no more website hacking due to locking of files from changes).
• Server configuration AutoFixer.
• cPanel Account Migration.
• TeamSpeak 3 Manager (Voice streaming).
• Shoutcast Manager (video streaming).

CENTOS WEB PANEL REQUIREMENTS

• A Static IP address
• Freshly installed operating system without any configuration changes.
• Minimum RAM for 32-bit 512MB and 64-bit 1GB with 10GB of free space.

Step 1. Configure Hostname

Note: hostname must be differnet from your main domain.(for example, if example.com is a domain on your server, use hostname.example.com as your fully qualified hostname).

You can use the following command for hostname setup eg. osradar.localhost.localdomain

# hostnamectl set-hostname osradar.localhost.localdomain

# hostnamectl

Step 2. Configure Server IP addresses

Here you will make configuration in your network interface file and assign your IP address.

# vi /etc/sysconfig/network-scripts/ifcfg-ens33

Step 3. Update the system

Use following commands to install and update server necessary updates.

# yum -y install wget

# yum -y update

# reboot

Step 4. Installing CWP on CentOS 7

Note: CWP installation can take more than 30 minutes, because it needs to compile apache and php from source.

# cd /usr/local/src

# wget http://centos-webpanel.com/cwp-el7-latest

# sh cwp-el7-latest

After installation a list of credentials will be appeared to access the panel. Make sure to copy or write down the login information. Once done, press “ENTER” for server reboot.

Step 5. Login CWP Admin Control Panel

Onece server reboot, login to your CWP on your web browser using the link provided by the installer on your server

http://SERVER-IP:2030/
Username: root
Password: your root password

Type username and password to login.

After logging in, it is recommended to make below configuration.

Setup Nameservers
DNS Functions > Edit Nameserver IP

Setup shared IP (must be your public IP address)
CWP settings > Edit Settings > write the shared IP(Normally main IP address already assigned)

Setup at least one hosting package
Go to package >add package > fill in the info and limits of the package

Setup root email
Go to CWP settings > Edit Settings > write the root email for the CWP

For more configuration instructions, please visit given link or comment bewlo.
http://wiki.centos-webpanel.com/

The post Install CWP (Centos Web Panel) on CentOS 7 appeared first on Linux Windows and android Tutorials.

Step: 1 Install Samba Server

Use below command to install samba with necessary packages.

# yum install samba samba-common samba-client -y

Step 2: Check Windows Workgroup

Before samba configurations, make sure Windows machine is in same workgroup.
open the cmd prompt in Windows machine and run the following command.

> net config workstation

Step 3: Samba Configuration

before configuration rename samba default configuration file /etc/samba/smb.conf as backup using below command.

# mv /etc/samba/smb.conf /etc/samba/smb.conf.default

Samba Anonymous File Sharing

Now create a shared folder on the server where all files/folders will be stored and set appropriate permissions on it and allow selinux for the samba configuration.

Run below commands

# mkdir -p /srv/samba/anonymous

# chmod -R 0755 /srv/samba/anonymous

# chown -R nobody:nobody /srv/samba/anonymous

# chcon -t samba_share_t /srv/samba/anonymous

Now make following changes in new samba configuration file.

# vi /etc/samba/smb.conf

[global]
workgroup = WORKGROUP
server string = Samba Server %v
netbios name = centos
security = user
map to guest = bad user
dns proxy = no

[Anonymous]
path = /srv/samba/anonymous
browsable =yes
writable = yes
guest ok = yes
read only = no

Run below commant to verify samba configurations

# testparm

Step 4: Start and Add Samba Services in firewall

Run below command to allow samba in firewall

# firewall-cmd --permanent --add-service=samba

# firewall-cmd --reload

Run below command to start and enable samba services.

# systemctl start smb.service

# systemctl enable smb.service

# systemctl start nmb.service

# systemctl enable nmb.service

Step 5: Access Shared folder

Now you can access the Centos shared folder from windows, open Run prompt by pressing win + r key on your keyboard then type \\centos and press enter key.

You will see Anonymous folder like below

Now you can add files/folders in this folder to share with other users.

The post Install Samba on CentOS 7 for File Sharing appeared first on Linux Windows and android Tutorials.

VNC (Virtual Network Computing) is a protocol which is used to remotely access user accounts by the Graphical User Interface.

Step 1: Install VNC

You need to use following command in order to install VNC. Makse sure you are login as root user.

# yum install tigervnc-server -y

Step 2: Setup VNC Password

After installation, login with the user you want to allow VNC remote access and and set VNC password for that user. I will enable VNC access to root user.

# su - user_name

# vncpasswd

Step 3: VNC Configuration

Now create a VNC file for your user. I template file vncserver@.service placed in below mentioned path, we will use copy of that file and make configuration for VNC user.

/lib/systemd/system/vncserver@.service

Use following command to make copy of vncserver@.service file.
Note: New file will be named as vncserver@:1.service

# cp /lib/systemd/system/vncserver@.service   /etc/systemd/system/vncserver@:1.service

Number 1 after @ sign represents the display number (port 5900+display). Secondly the port 5900 will be incremented by 1 with each started VNC server.

Now edit vncserver@:1.service file using following command.

# vi /etc/systemd/system/vncserver@\:1.service

and add the below lines in this file. Replace your_user with your username.

[Unit]
Description=Remote desktop service (VNC)
After=syslog.target network.target

[Service]
Type=forking
ExecStartPre=/bin/sh -c '/usr/bin/vncserver -kill %i > /dev/null 2>&1 || :'
ExecStart=/usr/sbin/runuser -l your_user -c "/usr/bin/vncserver %i
PIDFile=/home/You_user/.vnc/%H%i.pid
ExecStop=/bin/sh -c '/usr/bin/vncserver -kill %i > /dev/null 2>&1 || :'

[Install]
WantedBy=multi-user.target

save changes to file and quite

Step 4: Reload Necessary Daemons

After changes in file, reload systemd program to load new VNC configuration file and start the VNC server. Use following commands

# systemctl daemon-reload

# systemctl start vncserver@:1

# systemctl status vncserver@:1

# systemctl enable vncserver@:1

Step 5: Add Ports in Firewall

You must add VNC open ports in firewall so VNC client can access the system.
Use below command to list listening ports of VNC server

# ss -tulpn| grep vnc

Note: If you started multiple VNC instances for different users, the port value will be 5902 for the second, 5903 for the third and so on.

Use followings commands to add ports and reload firewall.

# firewall-cmd --permanent --add-port=5901/tcp

# firewall-cmd --reload

Step 6: Connect to CentOS Desktop from VNC Client

In order to access Centos desktop you need to install a VNC Client program, then run VNC Client and add the IP address and port number of CentOS VNC server and press enter button.

After that a warning will be displayed, click on continue button and enter VNC password on new screen.

Congratulations! You have access your Centos Desktop from VNC.

The post Install and Configure VNC console in Centos7 appeared first on Linux Windows and android Tutorials.

In this guide you will learn how to install and configure SquirrelMail step by step in Centos 7 and RHEL 7.

Step 1: First of all disable SELINUX using below command

this is not the best choice to disable the firewall because of security purposes, but we are doing this locally. in your case you allow the traffic vie the firewall-cmd rules.

# vi /etc/selinux/config

set SELINUX=disabled

save changes to file and quite

and reboot the server using below command

# reboot

Step 2: Install and Configure Postfix

You must install Epel Repository using below command

# yum install epel-release -y

Now install Postfix

# yum install postfix -y

Now make following changes to posfix file using below command at the end.

# vi /etc/postfix/main.cf

## Enter your hostname
myhostname = osradar.localhost.local

## Enter your domain name
mydomain = osradar.localhost.local

inet_interfaces = all
myorigin = $mydomain

##set your IP range
mynetworks = 192.168.130.138/24, 127.0.0.0/8

## set your mail direcotry
home_mailbox = Maildir/

## Now Go to line no 164 add $domain at the end
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain

save changes to file and quite

Restart Postfix

# systemctl restart postfix

# systemctl enable postfix

Step 3: Install and Configure Dovecot

# yum install dovecot

# systemctl start dovecot

# systemctl enable dovecot

Now modify below files one by one

make following changes at the end of file /etc/dovecot/dovecot.conf

# vi /etc/dovecot/dovecot.conf

protocols = imap pop3 lmtp

make following changes at the end of file /etc/dovecot/conf.d/10-mail.conf

# vi /etc/dovecot/conf.d/10-mail.conf

mail_location = maildir:~/Maildir

make following changes at the end of file /etc/dovecot/conf.d/10-auth.conf

# vi /etc/dovecot/conf.d/10-auth.conf

disable_plaintext_auth = yes
auth_mechanisms = plain login

make following changes to file /etc/dovecot/conf.d/10-master.conf

# vi /etc/dovecot/conf.d/10-master.conf

unix_listener auth-userdb {
#mode = 0600
user = postfix ## uncomment line 91 and enter postfix
group = postfix ## uncomment line 92 and enter postfix

Now restart Dovecot

# systemctl restart dovecot

# systemctl enable dovecot

Step 4: Install and Configure Squirrelmail

First install and start apache service

# yum install httpd -y

# systemctl start httpd

# systemctl enable httpd

Now install Squirrelmail

# yum install squirrelmail -y

Now go to squirrelmail folder and configure it according to your server

# cd /usr/share/squirrelmail/config/

# ./conf.pl

After changes press S to save settings and press Q to exit.

Now add following lines at the end of httpd.conf file.

Note: If these lines are already added at the end of file SKIP this step.

# vi /etc/httpd/conf/httpd.conf

Alias /webmail /usr/share/squirrelmail
<Directory /usr/share/squirrelmail>
Options Indexes FollowSymLinks
RewriteEngine On
AllowOverride All
DirectoryIndex index.php
Order allow,deny
Allow from all
</Directory>

save changes and quite

then restart Apache and dovecot service

# systemctl restart httpd

# systemctl restart dovecot

Step 5: Create User and Access Webmail

# adduser osradar

# passwd osradar

Finally access Webmail

http://server-ip/webmail

OR

http://yourdomainname/webmail

The post Install and Configure SquirrelMail in CentOS 7 appeared first on Linux Windows and android Tutorials.

Today, let’s learn to install CentOS on VirtualBox – the most popular virtualization software available. It’s open-source, cross-platform and offers the easiest environment for running virtual machines.

Getting CentOS

Before installing, we need to grab the installation source. In this case, we’ll be grabbing the CentOS ISO. Get the latest CentOS ISO. Make sure that you grab the “DVD ISO” that comes up with a medium collection of packages. The “EVERYTHING ISO” is a whopping 9GB ISO that contains all the CentOS packages, so not recommended (unless you’re sure that it’s what you need).

Don’t worry. Whatever you grab, the installation is going to be the same.

Setting VirtualBox

Fire up VirtualBox.

Click on “New”.

Enter the name and choose the version as “Red Hat (64-bit)”.

At the next step, enter the amount of RAM space you’re willing to assign for the virtual machine. Minimum is 2GB but recommended 4GB. If you can afford 8GB, it’s the best.

Now, it’s time to create a virtual hard disk.

Select “VDI” or “VHD”.

Choose “Dynamically allocated”. This way, the more you fill the virtual machine, the virtual hard disk will grow accordingly instead of grabbing all the spaces you’re about to assign.

Now, for installing CentOS, I recommend assigning 16GB of disk space.

The virtual machine is set.

Select the “CentOS” and press “Ctrl + S”.

From “System”, assign 2 processor cores (or threads). If your system has more cores, then you can easily assign more to the system.

From “Display”, assign the highest “Video Memory”.

From “Storage”, select the ISO you just downloaded.

Once the options are set, it’s time to fire up the virtual machine!

Installing CentOS

Start the virtual machine.

Select “Install CentOS 7”.

This is the first page of CentOS installation. Make sure to choose your preferred language.

Now, it’s time to set all the installation options.

After everyhing is set, begin the installation.

While the installation goes on, set “root” password and “user”.

Wait for the process to complete.

Reboot the system for completing the installation.

Accept license and connect to a network.

System is up! Login into your user account.

When starting the system, you’ll find out the initial GNOME setup window. Follow on-screen instructions.

Enjoy!

The post How to Install CentOS on VirtualBox appeared first on Linux Windows and android Tutorials.