The Elastic IP (EIP) service enables you to use static public IP addresses Internet bandwidths to connect your cloud compute to the Internet.

A security group implements access controls for ECSs, specifying the communication scope of ECSs. We can define different access control rules for a security group, and these rules take effect for all ECSs added to this security group. By default, a security group allows all data packets that are sent out from ECSs in it, and ECSs in the same security group can access each other.

A virtual private cloud (VPC) is a secured, isolated, logical network environment. You can create virtual networks in a VPC. The virtual networks provide the same network functions as those provided by a physical network and also advanced network services, such as elastic IP addresses and security groups.

To remote to Linux server we recommend two method that easy for you:

Method 1-Windows 10’s Built-in SSH Client:

To use the OpenSSH client on Windows 10,  we can open a PowerShell window or a command prompt window and run the "ssh" command. 

- Go to power shell or "cmd" command prompt 

Example: ssh steven@172.16.1.161 

- It will pop up allow you to type your password

Method 2-Use Putty:

We can use third party tool to remote linux server.

- Download putty  via this link  https://www.putty.org/

- After download, we have to launch putty and  select session  input your IP Address of your server with port

To create user we have to use command “adduser”:  

Example: we create username "dara"

 # adduser dara Or $sudo adduser dara

After user created, we can switch user that we just created:

Example: 

$ su dara

To change password user we have to use command “passwd “plus username:

Example:  I would to change password of username: steven

 # passwd steven

  Enter new UNIX password:

 Retype new UNIX password:

Note:

if you type the new password match, it will show “password updated successfully”.

The procedure to change the computer name on Ubuntu 18.04 LTS:

- Type the "hostnamectl" command

   $ sudo hostnamectl set-hostname Server 

- Edit and save the "/etc/hosts" file

  $ sudo nano /etc/hosts

- Reboot the system to changes take effect

  $ sudo reboot

To check real time of cpu and memory usage of Linux server recommend 3 method:

- "free" command is the most simple and easy to use command to check memory usage on Linux.

- "top" command is generally used to check memory and cpu usage per process. 

- "htop" command also shows memory usage along with various other details.

To check Disk Partitions and Disk Space on Linux, we would like to recommend you four commands:  

- "fdisk" is the most commonly used command to check the partitions on a disk. The fdisk command can display the partitions and details like file system type.

- "parted" command is another command line utility to list out partitions and modify them if needed.

- "df" command is not a partitioning utility, but prints out details about only mounted file systems. The list generated by df even includes file systems that are not real disk partitions.

- "lsblk" command lists out all the storage blocks, which includes disk partitions and optical drives. Details include the total size of partition, block and the mount point.

To check listening port in Linux Server we recommend you to user “netstat” command.

Here are the option usage with “nestat” command:

"-l" (for listening connections).

"-t" (for tcp connections).

"-p" (process name and id that opened the port).

"-n" (show port numbers instead of names).

Example:

"Iftop" command line uses the pcap library to capture the packets moving in and out of the network adapter, and then sums up the size and count to find the total bandwidth under use.  

To use "iftop" command line:

Step1: we have to add the repository  in “ /etc/apt/sources.list”.

"add-apt-repository main"

"add-apt-repository universe"

"add-apt-repository restricted"

"add-apt-repository multiverse"

Step2: we have update our server

$ sudo apt-get update

Step3: we can install “iftop” after server updated. 

$ sudo  apt-get install iftop

Example for usage of "iftop"

This server is accessing to https://wordpress.org and we track it by “iftop” command.

Linux Server has implemented a memory management efficiently and even more than that, but if any process is taking more our memory and we want to clear it, Linux provides a way to flush or clear ram cache.

Here is we prepare a schedule to clear memory cache in Linux Server: 

Step1: Create a shell script name as "clearcache.sh" under root (/root) partition with following commands

#!/bin/sh

sync; echo 3 > /proc/sys/vm/drop_caches

Step2: Set the permission of "clearcache.sh" script to 755

 # chmod 755 /root/clearcache.sh

Step3: Edit the system crontab file using below command

# crontab –e

Step4: Enter the following line in crontab file to set cron job for clearing cache automatically

0  0  *  *  0  /root/clearcache.sh

Note:

Append the above line, it is ruing at 00:00 every week.

Step4: Restart cron service to make it effect 

/etc/init.d/crond restart

The first thing to do is to check the status of SELinux on your system, and you can do this by running the following command:

“sestatus”

Example: 

#sestatus

SELinux status: enabled

SELinuxfs mount: /selinux

Current Mode: permissive

1. Disable SELinux Temporarily

To disable SELinux temporarily we have to use command below as root, we can use three method. 

- "echo 0 > /selinux/enforce"  

- "setenforce 0"

- "setenforce Permissive"

Note:

These methods above will only work until the next reboot

2. Disable SELinux Permanently

To permanently disable SELinux, we have to edit file "selinux" by using "vi /etc/sysconfig/selinux" command and change friom "SELinux=enforcing" to "SELinux=disabled".

After editing file, we have reboot server to make it works.

To disable root SSH login, we have to edit file in "sshd_config" by using command "vi /etc/ssh/sshd_config".

In addition, change "#PermitRootLogin yes" to "PermitRootLogin no". 

After changing the file, we have to save the file and restart ssh service by using "systemctl restart sshd" to make it works.

After  payment is successful, Server of customer will be created and hand over within 30 minutes.