USERS IN GNU/LINUX 

The first thing we need to know is that, in GNU/LINUX there are different types of users already predefined and each of them have different characteristics for the correct functioning of the system. The first of these is the root user.

Root user

The Root user is the administrator of the operating system, with all options and permissions to perform operations and changes in the system. Its main features are:

• It is the only user account with system-wide privileges.
• In charge of controlling the administration of user accounts.
• It is the only user that can stop the system.
• The root user can install, uninstall and update basic system programs and libraries.

In other words, the root user is the all-powerful user of the system.

Special Users 

They are also called users without login. Their roles in the system are determined by the addition of installed programs. They are distinguished by:

• They are created (usually) automatically at the time of Linux or application installation.
• It does not have all the privileges of the root user, but depending on the account they assume different root privileges.
• They are created when installing the system or any of its extra components.
• Some of them are: bin, daemon, adm, lp, sync, shutdown, mail, operator, squid, apache

Common Users 

These last users are us. That is, they are accounts that are created to use all accessible parts of the system, such as assigned programs and directories. They have a Home directory where they can easily access their documents and files.

• Such users have only full privileges in their working directory or HOME.
• They are used for individual users.
• These users do not have privileges to manage the system or install software. 

How to Create or Add USERS TO Linux Systems?

The adduser command is a “new” alternative to the useradd binary that allows us to add common users to our GNU/LINUX distribution. It is much more “friendly” and intuitive than useradd and allows us to add additional information about the new user. Here we will learn how to create user on Linux system.

In order to use the adduser command we must be root users, for that reason write the following command in a terminal

#Connect using su.
su

You need to write the root password then we can use adduser. The most basic way to use the adduser command is:

adduser new_user 

where new_user is the name of user account. With this “basic” form a new user is created and by giving Enter we are asked to enter the new password for this new user account.

Type the password for your new user account and press Enter. Prompt will ask you to reenter the same password. Re-enter the password and press enter button.

After that you will be asked for any additional information such as Full Name, phone number etc.

At the end, prompt will ask us to confirm the information provided. Type Y to proceed if all information is correct.

Now, as mentioned above, that is the most basic way to create a user but adduser also has options and alternatives to create users. These alternatives are given by the options that can be added to the command, some of them are:

adduser [--home DIR] [--shell SHELL] [--no-create-home] [--uid ID]
[--firstuid ID] [--lastuid ID] [--gecos GECOS] [--ingroup GROUP | --gid ID]
[--disabled-password] [--disabled-login] [--add_extra_groups] USER

You can see various options available with adduser command in above screenshot. Let’s look at example. If you would like to add a user named angelob, and set their home directory to /opt/angelob/ the the command will be as follows.

adduser --home /opt/angelob/ angelob

And then it will ask us for the new password and basic user information. This way you can add user to Linux system.

How to Delete Linux User Accounts? 

As in above section we have learnt how to create user on Linux system. Here i will explain how remove user from Linux system. Removing users from the Linux system is simple and the command to do so is userdel and has many fewer options to make the task. You can see the descriptions for this command in below image.

The easiest way to delete a user is to remove it by running below command. Here user is the name of user account.

#user is the name of user account.
userdel user

We can also delete your entire personal directory with the -r option. Run below command to do this.

userdel -r user

How to Modify Linux User Accounts? 

I have shown how to remove Linux user  in above section. Here, i will explain how to modify a Linux user. To modify users in the GNU/LINUX system we use the command usermod. We can see in the following image the possibilities shown in command:

For example, if we wanted to change the password of a created user, it would be as follows.

#user is the name of Linux user account.
usermod -p ‘new_password’ user

Obviously this method is not recommended because it leaves the password visible. Be careful. Read below article if you want to change your Linux user account password.

• How to Reset or Change User Password on RHEL?

Another useful example is to move the personal folder of the desired user to another one, for it we must combine the options -d and -m in the following way.

usermod -d /opt/angelob1/ -m angelob

With the rest of the options, we only have to place them according to our needs.

In conclusion we can say that the administration of GNU/LINUX users is a matter for system administrators, the subject is wide and with many options to take into account for the creation of them.

Adduser simplifies the creation of user accounts and usermod allows us to modify them in a very fast and dynamic way. And if a user has already completed his life cycle in the system, we can remove it with userdel.

I hope this small guide has been useful to understand a little bit about GNU/LINUX users, clarifying that the commands explained in the article can be used in all popular distributions such as Ubuntu, Red Hat, Suse, Debian and others.
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Read More:

• RHEL Interview Questions and Answers
• How to Change Hostname of RHEL system?
• How to Install and Use Htop to Monitor Linux Processes?
• Install Debian 9 Stretch in Step by Step Process

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Red Hat Linux Interview Questions and Answers

1. What is Red Hat Enterprise Linux?

Answer – It is a GNU/LINUX distribution created and developed by the multinational enterprise oriented company Red Hat, being the basis for deploying cloud applications, servers or data center.

2. Which is the package manager used by RHEL?

Answer – The package manager in RHEL is YUM.

3. How do I install a program in RHEL?

Answer – Installing a package or program in RHEL is simple thanks to YUM. With root permission we type in a terminal.

yum install package_name

4. How can I update the packages in RHEL?

Answer – Run below command to update all packages in your RHEL system.

yum upgrade

5. How can I remove the packages in RHEL?

Answer – Run below command to remove any package from RedHat Linux system.

#Make sure to change the name of package that needs to be removed.
yum remove package_name

6. How can I create a user in RHEL?

Answer – We can create a new user from the terminal with the command:

#Pass the user name in place of user_name 
useradd user_name

7. How can I change the user password?

Answer – The command that allows us to change the password of the active user is passwd. By entering the command in the terminal, you will be prompted for the current password and twice for the new password. Read below article to learn step by step process to change user as well as sudo passwords.

• How to Reset or Change User Password on RHEL?

8. How can I change the system language?

Answer- In RHEL, the system language can be changed using the following command:

localectl set-locale LANG=”xx_XX.utf8”

For example, if the system is in English and we want to change to German

localectl set-locale LANG=de_DE.utf8

Then simply restart the active session (not the system)

9. What is a GNU/LINUX service?

Answer – A service is a program that runs in the background, outside the interactive control of the users of the system.

10. How can I list the services that are running in RHEL?

Answer – This is very useful when managing systems in GNU/LINUX. We can list all the services that are running with the command:

systemctl -t service --state=active

If you want to check specific service running on RHEL then you can pass service name in above command. For example, i want to check SQL Server service running on my RHEL system then i will run below command. This command will show the output for only this service.

systemctl status mssql-server

11. How can I start or stop a service?

Answer – During the administration of a GNU/LINUX based server we will have to initialize and also stop services.

To initialize:

systemctl start name.service 

To Stop:

systemctl stop name.service

To Restart:

systemctl restart name.service

12. How do I know which version of the kernel I am using?

Answer – To know which version of the Linux Kernel we are using, just use the command:

uname –r

13. How can I add and remove kernel modules?

Answer – The kernel modules are small programs or libraries that are added to the kernel so that it can manage hardware devices. To add or remove it we use the command modprobe.

For example, to add a module:

modprobe module_name

And to remove a module

modprobe –r module_name

14. What is the file system RHEL uses?

Answer – The file system used by RHEL is XFS

15. How do I know how much space is available on my hard disk with RHEL?

Answer – This is useful to know when we are reaching the hard disk capacity. With the command:

df –h

16. Can I change hostname in RHEL?

Answer – Yes. There are multiple ways to change hostname of a RHEL system. For example if we want hostname to be example. com, we must write the following command in a terminal:

hostnamectl set-hostname example.com

I have explained it in below article in very details way. Have a look at this article to learn the process to rename or change the hostname of RHEL system.

• How to Change Hostname of RHEL system?

17. How do I know the IP address of the equipment in RHEL?

Answer – With the command:

nmcli dev show

We will not only be able to see the ip address, but also the complete information of all the network interfaces. You can read below article to learn how to check and change the IP address, subnet mask etc of a RHEL system.

• How to Find and Change IP Address, Subnet Mask and Default Gateway of RHEL system?

18. Can I install a Web server in RHEL?

Answer- Of course, we can install the web server we want: Apache, nGix or other.

19. After installing Apache2, where is the default Document Root located?

Answer – By default the apache2 DocumentRoot in RHEL sets it to /var/www/html/

20. How do I know which version of Red Hat Enterprise Linux is running the server?

Answer – Run the command in a terminal to get the RHEL version running on your system.

/etc/redhat-release

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Related Articles

• How to Change Hostname of RedHat Linux Server?
• How to Change IP, Subnet Mask and Default Gateway of RHEL Machine?
• Step by Step Process to Install RHEL 7.3

Change User Password in Linux

We will use passwd command to change our own password. Type passwd without specifying a username if you are changing your password. You will be prompted to enter your old password for verification, and then a new password. Below is the high level steps to follow password change process.

1. Open Linux terminal or connect to your server using PuTTY.
2. Type passwd and press Enter.
3. Type your current password and press Enter.
4. Now type your new password and press Enter.
5. Make sure your password is complex and not similar to older one otherwise you will get BAD PASSWORD error as shown in below screenshot.
6. Retype your new password and press Enter.
7. Now you will get notify that your password has been changed.

Change root Password

The “root” account is the most privileged account on a Linux system. When using this account, it is crucial to be very careful. Follow below steps to reset or change the password for your root account.

1. Open Linux terminal or connect to your server using PuTTY.
2. Type su at the command prompt, and press Enter.
3. Type the current root password, then press Enter.
4. Type passwd and press Enter.
5. Type a new password and press Enter.
6. Retype the new password and press Enter.
7. Your password is changed here.

Change other User’s Account Password

To change a password for a user, you need to login using “root” account. Follow below steps to change password on behalf of any user.

1. Open Linux terminal or connect to your server using PuTTY.
2. Type su at the command prompt, and press Enter.
3. Enter current root password, then press Enter.
4. Type passwd LoginName and press Enter. If login account is Manvendra. Type passwd Manvendra.
5. Enter a new password and press Enter.
6. Retype the new password and press Enter.
7. Your password is changed here.

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Related Articles:

• How to Change IP Address, Subnet Mask & Default Gateway of Linux Server
• Fix Error “User is not in sudoers file.
• Installing SQL Server 2017 on Red Hat Linux Server

There are three methods that i will explain here to rename or change hostname of any Redhat Linux server. These three methods that we will use in this article are given below.

1. Edit etc/hostname.
2. nmcli utility.
3. hostnamectl utility.

Change Hostname of RedHat Linux Server by editing etc/hostname

Connect to your Redhat Linux server and check the hostname by running below command.

#Check hostname using any command.
hostname

#You can run below command as well to check the hostname.
cat /etc/hostname

We can see the hostname of this RedHat Linux server is SQLServerRHEL.localdomain. Now we will change this name to TechyazRHEL. If you want to change hostname with fully qualified name then you can write fully qualified name in below command.

#Connect to RHEL as root.
Sudo su

#Change Hostname using /etc/hostname. Make sure to write your new hostname in double quote.
echo "TechyazRHEL" > /etc/hostname

You can see when we check hostname of this linux server using hostname command, it is still showing older name SQLServerRHEL.localdomain whereas when we check using cat /etc/hostname it is showing newly changed hostname.

To reflect new host name, we need to restart service systemd-hostnamed. Once you will restart this service, the output of hostname command will also be same as new hostname as shown in above image.

#Restart service systemd-hostnamed
service systemd-hostnamed restart
 or
systemctl restart systemd-hostnamed 

You can see new hostname after restarting above service in above screenshot. One thing you might notice that command prompt is still showing as older hostname i.e. root@SQLServerRHEL. This will disappear if you close this session and connect to new session. Let’s try this by launching new session, you can see new session is showing new hostname in below image.

Rename Hostname of RedHat Linux Server using nmcli

The nmcli (NetworkManager Command Line Interface) command-line utility is used for controlling Network Manager and reporting network status. nmcli is used to create, display, edit, delete, activate, and deactivate network connections, as well as control and display network device status. Here, we will use nmcli utility to change the hostname of redhat linux server.

Connect to your RedHat Linux server for which you want to change hostname. Run below commands to change hostname of your linux server.

#Connect to RedHat Linux server using root access.
sudo su

#Check existing hostname of RHEL server
hostname

#Change hostname of Redhat Linux server to techyazRHEL-nmCLI. 
#Change your new hostname in place of techyazRHEL-nmCLI.
nmcli general hostname techyazRHEL-nmCLI

#You can also check the hostname of Redhat linux server using nmcli utility.
nmcli general hostname

You can see hostname of RHEL server has been changed to techyazRHEL-nmCLI in above screenshot. Your PuTTY terminal will display new hostname once you open new session.

If new hostname is not showing after running above command then you should restart service systemd-hostnamed to reflect changes as we did in first section. You can see new hostname while launching new session in below screenshot.

Rename Hostname of RedHat Linux Server using hostnamectl

The hostnamectl tool is provided for administering the host names in use on a given system. First we will check the existing hostname of this server by running hostname command. We can also check the hostname using hostnamectl utility.

Connect to your Redhat Linux server using root and check the existing hostname.

#Connect to Linux server using root.
sudo su

#Check existing hostname.
hostname
or 
hostnamectl status

#Change hostname to techyazRHEL.
hostnamectl set-name techyazRHEL

You can check the hostname post renaming it. You can see new hostname in above image. Putty terminal will display new hostname once you open new session as shown in below image.

We can set all three kind of hostnames (Static, Pretty and Transient) using hostnamectl utility. Static name is mandatory whereas remaining two is optional. If you will not pass any hostname type in above command, same name will be set for all three hostnames. I haven’t used any hostname option in above command so all hostname options will have same name. Let’s check this in below image.

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Read More on SQL Server Installation on Linux Servers

• Installing SQL Server 2017 on Ubuntu Server
• How to Install SQL Server on Redhat Linux without Internet – Offline Installation
• How to Install SQL Server on Ubuntu without Internet access – Offline Installation
• Installing SQL Tools on RedHat Linux Server

Uninstall SQL Server 2017 on RHEL

Uninstalling SQL Server 2017 that is running on Linux server is totally different process as compared to its windows based SQL Server. Follow below step by step process to uninstall SQL Server 2017 from your RHEL Linux server.

1- Connect to your RHEL server where SQL Server 2017 is running and that needs to be uninstalled from the server. Check whether SQL Server is installed on this machine or not by checking SQL Server service. You can see SQL Server is running on this server.

#Run below command to check SQL Server Service.
systemctl status mssql-server

2- Check SQL Server files along with the database files before removing SQL Server. We will validate SQL Server removal by checking these files post uninstallation.

#Check SQL Server binaries & database files
sudo ls -lrt /var/opt/mssql
sudo ls -lrt /var/opt/mssql/data

Note: Make sure to run full backup of all your databases and keep them in a safer place for future needs.

3- Now, we will uninstall SQL Server by running below command.

#Remove SQL Server from your Linux machine
sudo yum remove mssql-server

You can see details of SQL Server packages that are going to be removed from this machine. These packages are SQL Server and SQL Server Agent that are going to be removed here. Above command will ask us to type y to proceed with the uninstallation and type N to quit this uninstallation. Type y to proceed with the SQL Server removal.

You can see SQL Server and SQL Server Agent both packages have been removed from this machine.

4- Now, remove all SQL Server binaries and database files from its installed location that we checked in second screenshot by running below command.

#Remove database files and SQL binaries.
sudo rm -rf /var/opt/mssql

Here, your SQL Server has been removed from this linux machine. You can check SQL Server binaries and database files by running below commands. We can see no files in these locations because they have been removed now.

#Check database files.
sudo ls -lrt /var/opt/mssql/data

#Check SQL Server files & folders.
sudo ls -lrt /var/opt/mssql

5- Now you can check SQL Server service again by executing below command.

#Check SQL Server Service post SQL Server Removal.
systemctl status mssql-server 

We can see SQL Server is not loaded this time but service is showing as active.

When you will try to restart this service, it will throw you an error that unit not found as shown in below image.

6- Now we need to reboot the server to update SQL Server service status on RHEL. I restarted this linux machine and again checked the SQL Server service. You can see this time it says service could not found.

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Missing Features in SQL Server on Linux

Below is the list of features that are not supported on Linux based SQL Server instances as of now in current GA release of SQL Server 2017.

1. Analysis Services
2. Reporting Services
3. R Services
4. Master Data Services
5. Data Quality Services
6. SQL Server Browser Service
7. Transactional & Merge Replication
8. FILESTREAM
9. FileTables
10. Stretch DB
11. Polybase
12. Third Party Extensions
13. XPs
14. VSS Snapshots
15. Buffer Pool Extension
16. Change Data Capture
17. Alerts
18. Distributed query with 3rd-party connections
19. Database Mirroring
20. AD Authentication for Linked Servers & Availability Groups (AGs)
21. SQL Server Integration Services (SSIS)

The mssql-server-is package (SSIS) is not supported on SUSE Linux in this release. It is currently supported on Ubuntu and on Red Hat Enterprise Linux (RHEL) only.

The following features are not supported in this release when you run SSIS packages on Linux:

o SSIS Catalog database
o Scheduled package execution by SQL Agent
o Windows Authentication
o Third-party components
o Change Data Capture (CDC)
o SSIS Scale Out
o Azure Feature Pack for SSIS
o Hadoop and HDFS support
o Microsoft Connector for SAP BW

For a list of built-in SSIS components that are not currently supported, or that are supported with limitations, see Limitations and known issues for SSIS on Linux

Related Articles:

• Install SQL Server on Ubuntu Server
• How to Install SQL Server on RHEL
• New features Introduced in SQL Server 2017
• Install SQL Server on Ubuntu without Internet Access

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Network error: Ubuntu ssh Connection Refused

I faced ubuntu connection refused error while establishing a connection to Ubuntu Linux virtual machine from host computer. I installed PuTTY on my host and tried to connect to Ubuntu Linux machine. Let’s check the IP of Ubuntu server that we had used to make connection from PuTTY terminal. Run ipconfig command to get these details.

#Check IP of Ubuntu Server
ipconfig

We can see the IP details of the Ubuntu server that is showing 192.168.209.134. We have used this IP to establish server connection and end up with this PuTTY fatal error.

I tried to connect to Ubuntu server post getting IP from above command but I got ubuntu ssh connection refused error during this operation. The details of PuTTY Fatal Error that caused ubuntu connection refused is given below.

Solution

We faced ubuntu ssh connection refused error and failed to connect to Ubuntu Server remotely using PuTTY terminal because SSH, or Secure Shell is not installed on the Ubuntu server. SSH, or Secure Shell, is a protocol used to securely log onto remote systems. Our next step is to install SSH on the Ubuntu server. Run below command to start this installation.

#Install SSH on Ubuntu Server
sudo apt-get install openssh-server

It will check the dependencies and ask you to type y to proceed with the installation as shown in below image.

A series of all required packages will download and set up to install SSH. Once SSH will be installed on your Ubuntu server it will look like below image.

You can also reconfirm the installation by executing same command which you ran to install it. You can say, it is saying newest version is already installed on this server.

Now launch PuTTY terminal on your host computer or a computer from where you want to connect to the Ubuntu server and enter IP address of Ubuntu server to establish connection. Once you click on connect button, you will get a window for the very first time only. Click on Yes button of that window to proceed. Once you will click on Yes button you will be connected to your Ubuntu server remotely.

Now we can see putty connection refused error is fixed and we can connect to Ubuntu server remotely using PuTTY terminal. If you want to change configurations of SSH you can refer to attached document. This way you can fix ubuntu ssh connection refused error.

Here, we have fixed ubuntu putty connection refused error. I hope you like this article. Please follow us on our facebook page and on Twitter handle to get latest updates.

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Check IP Address, Subnet Mask & Default Gateway

Launch PuTTY and connect to Linux server. Run ifconfig command.

#Check IP address and Gateway Mask
ifconfig

You will see output of this command like below screenshot.

Focus on the area which is highlighted in red colour. The IP address of this Linux server is 192.168.0.1 which is labeled as inet. You can see the subnet mask of this server which is showing 255.255.255.0 as netmask. We can also see the connection interface name of this machine that is ens33. The connection interface name will be used later in next section during changing IP addresses, subnet mask and gateway details.

Now we knew how to check the IP Address & Subnet Mask of your Linux computer. Now next step is to check the default gateway of this server. Run below command route -n to get the details of default gateway.

#Check Default Gateway
route -n

We can see the gateway IP is given in below screenshot for the same connection interface name ens33.

Change IP Address, Subnet Mask & Default Gateway

We knew how to get the IP address, subnet mask and gateway details of Linux server. Now i will explain how to change these addresses if needed. We will use same command ifconfig to change the IP address and subnet mask. Before proceeding, make sure you have interface name and new IPs. You can get interface name from ipconfig command. The connection interface name of my machine is ens33 as shown in above screenshots. Run below command to change these two values.

#Replace ens33 to your connection interface name. You can get it from ifconfig command.
sudo ifconfig ens33 192.168.209.10 netmask 255.255.255.0

We can see command executed successfully. You can validate the new IP address by running ifconfig command again. I have not changed netmask and kept same. If you want to change it please pass your netmask address.

Now we can see we have changed the IP address and netmask address for this Linux server. Next we can check the gateway address to validate what will be the impact on gateway post changing the IP address and netmask address. Run route -n again to get the details.

We can see gateway address is not set yet and the one showing on first section is not showing now. So let’s change the gateway address for this server. Run below command to change the gateway address.

#change the name of gateway address. Change the connection interface name from ens33 to your name.
sudo route add default gw 192.168.209.250 ens33

Once command will be executed successfully, you can validate this change by running route -n command again.

We can see the new gateway address in above screen. These are the commands that can be used to check and change the IP address, netmask address and gateway address.

Related Articles

• How to Change Hostname of RedHat Linux Server?
• Reset or Change Linux Passwords for users and root?
• How to Change PuTTY Background Color to White?

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Before going ahead, we need to have a RedHat Linux server. If you have no idea about installing Linux server or creating a virtual machine where you can install Linux and SQL Server then i would recommend you to read below articles first.

• How to Create a Virtual Machine.
• Install RedHat Linux 7.3 on a virtual machine.
• How to Install SQL Server on RedHat Linux 7.3

If you have installed SQL Server on Red Hat Linux server, your next step should be to install SQL Server Agent on that server. Make sure you have internet access on the Linux server where we are going to install SQL Server Agent. If your server does not have internet connection then you should read attached article about installing SQL Server Agent on RedHat Linux that are running without Internet.

Install SQL Server Agent on RHEL

As this Linux machine has internet connection so let’s go ahead with Installation on Red Hat Linux server. Installation process is quite similar to the installation of SQL Server on Redhat Linux.

You don’t need to download SQL Server Agent package separately the way we did for SQL Server and SQL Tools installations.The package required to install SQL Server Agent included into SQL Server package repository configuration file.

If you have already downloaded SQL Server package repository configuration file to install SQL Server, you can skip this step and go ahead to install Agent on your server. If you don’t have SQL Server package repository configuration file or you have deleted it then you can run below command to download the package repository configuration file.

#Download Microsoft SQL Server Red Hat repository configuration file
sudo curl -o /etc/yum.repos.d/mssql-server.repo https://packages.microsoft.com/config/rhel/7/mssql-server.repo

This will download Microsoft SQL Server Package Repository Configuration File that are required to install SQL Server and SQL Server Agent.

As we have the Agent repository configuration file now, Let us first check the SQL Server in SSMS to see how SQL Server Agent working.  You can see we are not able to do anything in SQL Server Agent folder.

Now our next step is to install SQL Server Agent to enable its related features. Run below command to start the installation.

#Install SQL Server Agent
sudo yum install mssql-server-agent

You cans see series of executions started to proceed with the installation in below image. It will also ask you to enter Y to proceed.

Enter Y to proceed with the installation, once you press enter it will proceed to install. Now SQL Server Agent will install on your machine.

It will also suggest you to restart SQL Server service. If you will not restart SQL Server service, installation will not be completed so next step is to restart SQL Server service on this server.

#Restart SQL Server Service
systemctl restart mssql-server

You can see SQL Server is online now. Go ahead and connect to SQL Server in SSMS as per below image.

Now you can create Agent jobs to automate database activities on your SQL Server instance.
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Prerequisites

Before going ahead, we need to have a RedHat Linux server. If you have no idea about installing Linux server or creating a virtual machine where you can install Linux and SQL Server then i would recommend you to read below articles first.

• How to Create a Virtual Machine.
• How to Install RedHat Linux 7.3 on a virtual machine.

Below are the prerequisites that needs to have on your virtual machine in order to install SQL Server 2017.

• A Red Hat Linux Machine having Internet Connection
• RAM – 3.25GB
• Disk Space – 6GB
• Processor speed – 2 GHz
• Processor cores – 2 cores
• Processor type – x64

Install SQL Server 2017 on RHEL

Installing SQL Server 2017 on Redhat Linux is straight forward method if your server has internet connection and able to access online repositories. But if your Red Hat Linux machine does not have internet connection you can go with attached article Offline Installation of SQL Server 2017 on Red Hat Linux. Let us go with the SQL Server Installation on Redhat Linux server that have internet connection.

Connect to RHEL server locally or through PuTTY. Check whether SQL Server is previously installed on this machine by someone else or not. You can see SQL Server is not installed, we can see it by checking the SQL Server service. Now download the Microsoft SQL Server Redhat repository configuration file by running below curl command.

#Download Microsoft SQL Server Redhat repository configuration file
sudo curl -o /etc/yum.repos.d/mssql-server.repo https://packages.microsoft.com/config/rhel/7/mssql-server.repo

Next step is to install SQL Server on Linux machine. Run below command to update all package repository on Red Hat Linux server.

#Update Packages
sudo yum update

#Install SQL Server
sudo yum install -y mssql-server

I ran installation command which is showing in below image. A series of execution will start followed by checking the dependencies. If you will face any dependency issue, you should first resolve all missing dependencies then proceed with the installation. Setup will process and show you details of the packages which will be installing. You can see the details in below image.

SQL Server package is in downloading process. Once download will complete, installation process will start. This will take few minutes to install the package.

Now you can see SQL Server database engine is installed on this Redhat Linux server. Installation is not completed yet because setup suggests us to run mssql-conf utility to complete the installation. So next step is to run this process.

Setup is suggesting us to install a mssql-conf utility to accept the license terms and set the sa password. Run below command to configure SQL Server.

sudo /opt/mssql/bin/mssql-conf setup

This execution will ask us to accept the License terms, select the SQL Server edition and also tell us to set the sa password. Let us do that to complete this installation. Once you execute above command, it will ask as to enter YES to access the license terms. Type YES and press enter. Once you press enter post accepting license terms, setup will give you options to choose SQL Server edition. Select correct edition as per your requirement.

Once you choose SQL Server edition, it will ask you to set sa login password. The moment you set the sa password, SQL Server configuration will be completed and ready to use.

Now SQL Server is installed, but sometimes you may face issue connecting to your SQL Server instance. You need to run below commands to open the SQL Server port on the firewall on the Linux server.

#Open Firewall for SQL Server
sudo firewall-cmd --zone=public --add-port=1433/tcp --permanent
sudo firewall-cmd --reload

You can see above commands executed successfully. Port 1433 is already enabled on my machine. If this port is not open on your server it will display as success. Now, you can check the SQL Server service to validate this installation. Run the same command which we have run to check the SQL Server service before starting the installation.

#Check SQL Server Service
systemctl status mssql-server

Now your SQL Server is ready to use. You can connect to this instance using SSMS client tool. You can see i have connected to this instance using SSMS from my local host computer.

If you want to connect to SQL Server on this server only. You need to connect using sqlcmd utility. By default, sqlcmd tool does not install on Linux machine. We need to manually install it. Please visit this attached article to understand step by step process of installing SQL Tools on a Red Hat Linux Server. If you don’t have internet access you can follow another article to install SQL Tools on Redhat Linux server in Offline mode.

If your Linux virtual machine doesn’t have Internet connection, you should read:

• How to Install SQL Server 2017 on RedHat Linux in Offline Mode.
• Installing SQL Tools on RedHat Linux in Offline Mode.
• Install SQL Server Agent on RHEL running without Internet.
• How to install SQL Server on Ubuntu in Offline Mode.

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Linux Error: User is not in the sudoers file. This incident will be reported.

Sudoers file determines which users can run administrative tasks, those requiring superuser privileges. I was failed to perform certain tasks because my username was not part of this file and returned with below error.

Linux Error: User is not in the sudoers file. This incident will be reported.

Someone who has super user (su) access can fix this issue by adding the impacted user to the Wheel group. The wheel group is a special user group used on Linux systems to control access to the sudo command, which allows a user to behave as super user. Once we will add our user into this group, we will be able to use sudo command.

Adding a Linux User to Sudoers File

Connect to your Linux server using superuser account.

#Connect using su
su

We have now connected to Linux server using superuser account. Now we can add our username to the Wheel group.

#Add your user to the Wheel group. 
#Change techyaz to your user name.
usermod -G wheel techyaz

Now we see that command executed successfully. If you attempt to execute the sudo command now, you might get the same error message unless you completely logout your user and re-login again. Next you can exit from superuser account by typing exit on the prompt.

#Exit su account
exit

Your account or user added to sudoers file now by adding it to wheel group. You can now connect to Linux server from your PuTTY terminal or on the local server and try to run sudo command post completely logout your user and re-login on the server.

#Connect to Linux server using your user name that was added to wheel group.
#Run sudo su
sudo su

You can see we have access to run anything using sudo command in above screenshot. Now your username is part of sudoers file so you can perform your activities using sudo command now.

Read more:

• How to Install Red Hat Linux 7.3 on Virtual Machine
• Fixing PuTTY connection issue while connecting to Red Hat Linux Server
• Installing SQL Server 2017 on Red Hat Linux Server

Here, we have fixed Linux error “User is not in the sudoers file. This incident will be reported.” I hope you like this article. Please follow us on our facebook page and on Twitter handle to get latest updates.

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Network error: Connection timed out

I faced this issue during making connection to Linux virtual machine from PuTTY terminal that is running on host computer. I got below error during this operation. When i tried to ping the Linux virtual machine from host it was failed and shown request timeout.

I did some research over internet and found lot of solutions and reason behind this issue. Some people suggested to check and disable all firewalls and some has suggested some other solutions. Most of solutions have failed to fix this issue.

I discussed it with one of my friend who works in VMware domain, he suggested only one solution to check the IPs of host and virtual machine that should be part of same subnet. I apply his solution and it worked. Here i will explain the fix of this issue.

Let’s check the IP of local host on which Linux virtual machine is hosted. Run ipconfig command to get these details.

#Check Host IP
ipconfig

We can see the IP details of the host computer. We can see the range of IP is 192.168.209.1 & subnet mask is 255.255.255.0

Now we will check the IP of the Linux virtual machine which we generally give during the installation. Run ifconfig command on your Linux machine.

#Check Red Hat Linux Server IP
ifconfig

You can see the IP of this machine is 192.168.0.1 that belongs to different IP range. This is the main issue behind this error. Our next step to change the IP of Linux machine to same IP range under which host is running.

Solution

The solution of this issue is to change the IP of Linux machine to the same range on which local host is running. We can see the connection interface name is ens33 from above screenshot. Next step is to connect to Linux machine and set the new IP for this connection interface name. Run below command to get this done.

#Change the IP of connection interface name ens33 to 192.168.209.10.
sudo ifconfig ens33 192.168.209.10 netmask 2555.255.255.0

We can see command executed successfully. Now we can validate this change by running ifconfig again and you can see the IP is changed to 192.168.209.10 now.

Now we can go ahead and connect to this machine from host computer. Launch the PuTTY tool and enter the IP of the Linux virtual machine and click on open button as shown in below screen.

Once you click on open button, another window will come and ask you to choose Yes to proceed. Click on Yes button of this screen to proceed. Once you click on Yes button, you will get a login window which ask you to enter a correct login id and password to connect to Linux virtual machine. I did the same and you can see i have successfully connected to the Linux virtual machine from my host computer.

Now issue is fixed and you can do anything as per your requirement on the Linux virtual machine from your host computer using PuTTY terminal.

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Read More:

• Fix PuTTY Network Error: Connection Refused While Connecting to Ubuntu Server
• How to Change PuTTY Text Color?
• How to Change Putty Cursor or Mouse Pointer Color?
• Change PuTTY Background Color

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How to Install Red Hat Linux 7.3?

I have performed this installation on one of my virtual machine that are hosted on my local computer. If you want to create new virtual machine to install Linux 7.3 operating system you should read its step by step process in attached link.

Once you have created your virtual machine with RHEL 7.3 setup, installation media will automatically be detected and let you proceed with the installation. This is because you have already selected RHEL 7.3 ISO during virtual machine creation. Make sure you have downloaded correct RHEL setup file. Below is the image of correct setup file.

Now let us proceed with the installation. You will get below image to proceed with the Linux installation once you finish creating a virtual machine.

Press enter on first option “Install Red Hat Enterprise Linux 7.3” to proceed with installation. If you will not press enter, setup will start automatically after 1 minute. Now you will get below screen which says to press enter again.

Once you press enter, a series of updates will process on your screen.

You will get below screen to choose the language in the next window. Here choose your language in which installation texts will proceed and click on “Continue” button to proceed.

Next window will be “Installation Summary” window from where we will configure all configurations for this installation. You can see “Begin Installation” button is showing disabled on this window. It will enable the moment we configure all parameters. We will click one by one to each option and then configure them with the correct value to proceed.

Let’s start the configuration one by one. First click on “Date & Time” option to set the server clock according to your time zone. As i stayed in India so i have chosen region as Asia and city as Kolkata and then set the time and date in the bottom of below screen. Now click on done button given top left side of the below image.

Now click on “Keyboard” option to set the keyboard option as shown in below image. Click on plus sign if you want to choose some other settings. Click on done button to apply this change for the installation.

Now click on “Language Support” option to set the language for this installation. Choose your language and click on done button to proceed.

Next option in installation summary window is to select correct installation media. I did not make any changes here because it is already selected as local media which we had downloaded from Red Hat website.

Now click on “Software Selection” to choose what type of installation you want to proceed. I selected minimal install to proceed. If you want to install GUI based Linux server operating system you can choose last option of below screen. Once you made your selection click on done button to proceed.

Now we will configure the “Installation Destination” option.Here we have also an option to configure storage partitioning. If you want to add some other disk you can do that as well from this page. I have selected 20GB for this Linux server so it is shwoing there. Now come to the storage partitioning section which is in bottom of the screen, i have selected “Automatically configure partitioning“. Setup will configure all the partitions automatically during installation. If you want to configure it manually you can choose second option that will allow you to configure as per your need. Click on done button to proceed, once you have made all changes.

Now there are only three option left to configure as per below image. These are Kdump, Network & Hostname and Security Policy. You can see rest of all options are showing with their configured value.

Now click on KDUMP option. Kdump is a mechanism which captures information from your system during system crash that can be invaluable in determining the cause of the crash. I have enabled this option. If you do not want to enable it you can uncheck it. Click on done button to proceed.

Now click on “Network & Host Name” option. You will get below image to configure it.

Now click on on/off button showing in top right side of above screen. It will automatically assign IP address, subnet mask address to make connection. I have enabled it and you can see all address in below screen. You can also change the hostname of Linux server. Write the server name in the host name section and click on apply button.

If you want to assign IP address, subnet mask address and other details manually you should click on configure button on below screen. Click on done button to proceed.

Final option is to select appropriate Security Policy. I did not make any changes and go with default option as shown in below screen.

Now we will click on “Begin Installation” to start the installation.

Once installation will begin, you will get below progress status bar along with options to set Root Password and User Creation.

Click on Root Password option of above screen to set the root password. Click on done button once you have entered the password.

Now click on User Creation option to create an user. I have created an user named techyaz as shown in below screen. Click on done button to proceed.

Now you can see text written in red colour is disappeared from root password and user creation options. Installation is still in process during the user creation. You can see below screenshot.

Once installation will be completed below screen will come that will say that installation of Linux 7.3 operating system is completed.

Now Reboot button is enabled and setup also suggested to reboot the server. Click on reboot button to restart the server. Your Linux installation has completed here.

Now we will validate the installation by running few commands. Once server will come online post reboot, it will give you below prompt to enter the login credentials.

Enter the user name which you have created during installation. You can see now i have connected to Linux server using user techyaz.

Now you can check the hostname and RHEL version installed on this machine by executing below commands.

Now we can see the output which says host name as SQLServerRHEL and its version RHEL 7.3 in above image.

I hope you like this article. You can comment about your questions in comment section. Please follow us on our facebook page and on Twitter handle to get latest updates.

Read More:

• RHEL Interview Questions & Answers
• Step by Step Process to Install Ubuntu Linux 16.04
• How to Install and Use Htop to Monitor Linux Processes?
• How to Install Zabbix on Linux Machine?

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Install VMware Workstation

VMware workstation is the industry standard for running multiple operating systems as virtual machines on a single PC. Thousands of IT professionals, developers and businesses use Workstation Pro to be more agile, more productive and more secure.

First task is to install VMware workstation on your PC or laptop post downloading it from VMware website. Once you install VMware workstation on your system, you can see the vmware workstation shortcut icon on your desktop.

Create a Linux Virtual Machine

As we are creating a Linux machine so we should have the correct setup file of RedHat Linux. Copy RedHat Linux setup file to your machine and if you don’t have this setup file you can download it from RedHat Website. Make sure to download RHEL binary DVD ISO file. If you download some other file you might face issue during installation.

Now you have installed VMware workstation and downloaded Linux setup file successfully. Next step is to create a Linux virtual machine. Double click on the vmware workstation shortcut icon which is created on your desktop during installation to launch it. You will see below screen to proceed.

Now click on “Create a New Virtual Machine” option which is showing in right side pane of above screen. You will get a welcome window named “New Virtual Machine Wizard” to proceed. There are two configuration options on this page. Don’t make any change here and go with the default option which is “Typical”.

Click on next button to proceed. Next window is for choosing your operating system for this Linux machine. Here we will select the Linux setup ISO file which we have downloaded in above step along with the full path. You should select your identified operating system setup file here if you want to install some other operating system. You can click on browse button to choose the correct path.

We have also an option to install operating system later post creating the virtual machine. If you want to install your OS later you can select 3rd option of this page. As we have downloaded the setup file of RHEL so we will choose and proceed with 2nd option. Once you select the setup file click on next button to proceed.

Next screen will come to configure the name of this new virtual machine and the location where you want to save or create this machine. Choose a name as per your convenience and browse the location where you want to create this machine on local system. Make sure you should have enough disk space where you are creating this virtual machine.

Once you configure the name and location of this virtual machine in above step, next step to specify the disk size. As i am creating it for my server lab so i will go with default value which is 20GB. Make sure to have that much space on your drive where you have created this virtual machine in above step.

Next window will be the final screen of this setup. Here you can verify the details which you are using to create the Linux virtual machine.

We can see there is only 1GB of memory allocated to this machine. If you want to change such configuration before creating the Linux virtual machine then click on “Customize Hardware…” to alter the changes. Change the value to allocated memory and CPU as per your need. You can also make changes of other configurational parameters. Click close once you are done with your changes.

Now you can see memory is showing the new value along with the CPU which i changed from 1 to 2. you can compare below screen with the one showing above. Now click on “Finish…” button to create your Linux virtual machine. Once you click on finish button, Linux virtual machine will be created and Linux installation will be proceeded. If you are not aware of Linux installation and want to learn step by step process to install Red Hat Linux on this server you must read attached link.

Now you can create multiple virtual machines running on your computer. Follow the same process if you want to create another servers. I hope you like this article. Please follow us on our facebook page and on Twitter handle to get latest updates.

Read More:

• Step by Step Process to Install RHEL 7.3
• Step by Step Process to Install Ubuntu Linux 16.04
• How to Install Debian 9 Stretch?

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