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

The post Linux User Administration – Add, Delete & Modify User Accounts appeared first on Techyaz.com.

If you are facing different kind of DROP login failed errors, you can read below articles where i have demonstrated step by step method to fix the various kind of DROP login failed errors:

• How to fix Error 15174: Login owns one or more databases.
• How to fix Error 15173: Revoke the permissions before dropping the login.
• How to fix error 15138 & Error 3729: DROP login failed
• How to fix error 15141: The server principal owns one or more endpoint(s) and cannot be dropped
• How to fix error 15434: Could not drop login as the user is currently logged in

Microsoft SQL Server Error 15170

I had to remove a SQL login on one of SQL Server instance where AlwaysOn Availability Group is configured and running. We need to remove this login and recreate it with the same SID which are present on primary replica to fix an AOAG Automatic failover issue. Login was failed to drop because of SQL Server error 15170 which suggests that this login owns one or more SQL Server Agent jobs. Error details are given below.

As error clearly says, that one or more Agent jobs are owned by this login so let us check the details about it. Expand SQL Server Agent followed by Jobs folder of your SQL Server Instance connected in SSMS. You can see below jobs were there on SQL Server Instance.

Solution

Now check the properties of these agent jobs to check the job owner. Double click on identified agent job. You will get below image. Here you can see job owner is showing as same account which we are trying to drop. Change it to sa and click on ok button to apply the change. Repeat the same to the all three agent jobs.

Now owner of agent jobs is changed to sa. Next step is to go ahead and drop the login again. you can do it by either SSMS or T-SQL. SSMS way is given below:

• Connect to target SQL Server Instance.
• Expand the security folder.
• Expand the Logins folder.
• Right click and choose delete on the identified login which needs to be deleted.
• Click on Ok button of the login deletion window.

If you want to drop this login using T-SQL command then open a query window and execute below command.

--change the name of Login_name with your login name which you want to delete.
DROP Login 'LOGIN_NAME'

This time your login will be dropped successfully. If you are still facing some another issue during dropping this login, you can read below articles where i have demonstrated step by step method to fix the DROP login failed errors:

• How to fix Error 15174: Login owns one or more databases.
• How to fix Error 15173: Revoke the permissions before dropping the login.
• How to fix error 15138 & Error 3729: DROP login failed
• How to fix error 15141: The server principal owns one or more endpoint(s) and cannot be dropped

Here, we have fixed Microsoft SQL Server error 15170. I hope you like this article. Please follow us on our facebook page and on Twitter handle to get latest updates.

The post Fix SQL Server Error 15170: Login owns one or more Agent Jobs appeared first on Techyaz.com.

If you are facing different kind of DROP login failed errors, you can read below articles where i have demonstrated step by step method to fix the various kind of DROP login failed errors:

• How to fix Error 15174: Login owns one or more databases.
• How to fix Error 15173: Revoke the permissions before dropping the login.
• How to fix error 15138 & Error 3729: DROP login failed
• How to fix Error 15141: Server principal owns one or more endpoints.

Microsoft SQL Server Error 15434

This error generates when a login has made a connection to the SQL Server Instance and you are trying to drop the same login. Solution to fix this issue is to close all sessions which are opened by this login and then drop it. You can get the details about the sessions which are open using this login id either by sp_who2 or by DMV sys.dm_exec_sessions.

I had to remove a domain login on one of SQL Server instance but login was failed to drop because of SQL Server error 15434 which suggests that the login is currently logged in. Error details are given below.

Drop failed for Login “domain\abc”
Could not drop login ‘domain\abc’ as the user is currently logged in. (Microsoft SQL Server, Error: 15434)

As error clearly says that above login is currently logged in. Run below T-SQL code to get the details about the sessions or connections this login has made to the SQL Server Instance.

SELECT login_name, * FROM sys.dm_exec_sessions
WHERE login_name = 'xyz\abc'
Go

You will see the details for this login along with the session id in below screenshot.

Solution

Now we have identified the session id which are running using this login id which we want to drop. Now next step is to kill this session. Make sure to check the SQL code running behind this session id. If it is not critical go ahead and drop the login or if any DML or other operations are running about which you are not aware of, please contact application owners to get the details about this session id. Don’t kill any session id that you are not aware of. Now go ahead and kill above session which is running using our login id. I am going ahead to kill this session because i know what is running under this session which is not critical.

--Replace the session id 53 with your session id.
Kill 53
GO

We can see command executed successfully. You can recheck whether this session is still open or not by executing same command which we have executed in first section.

We can see, session id 53 is no more active and disappeared from the SQL Server transactions. Next step is go ahead and drop the login again. This time your login will be dropped successfully.

If you are still facing same issue during dropping the login and get this error again then you can check SQL Server services log on accounts. Sometimes if you run SQL Server services using the account which you want to drop throws same error. If this is the case then your next step is to change the logon account to some other domain account to release this login. You can see this in below image. Change the log on account of all SQL Server services if they are running using this account. Once you made the changes to the services, restart SQL Server service to bring new account in use by SQL Server.

Now go ahead and drop the account again. This time it will work and your login will be removed. You will not face Microsoft SQL Server Error 15434 anymore. You can do it by either SSMS or T-SQL. SSMS way is given below:

• Connect to target SQL Server Instance.
• Expand the security folder.
• Expand the Logins folder.
• Right click and choose delete on the identified login which needs to be deleted.
• Click on Ok button of the login deletion window.

If you want to drop this login using T-SQL command then open a query window and execute below command.

--change the name of Login_name with your login name which you want to delete.
DROP Login 'LOGIN_NAME'

If you are getting some another issue during dropping this login, you can read below articles where i have demonstrated step by step method to fix the DROP login failed errors:

• How to fix Error 15174: Login owns one or more databases.
• How to fix Error 15173: Revoke the permissions before dropping the login.
• How to fix error 15138 & Error 3729: DROP login failed
• How to fix Error 15141: Server principal owns one or more endpoints.

I hope you like this article. Please follow us on our facebook page and on Twitter handle to get latest updates.

The post Fix SQL Server Error 15434: Could not drop login ‘Domain\abc’ as the user is currently logged in appeared first on Techyaz.com.

If you are facing different kind of DROP login failed errors, you can read below articles where i have demonstrated step by step method to fix the various kind of DROP login failed errors:

• How to fix Error 15174: Login owns one or more databases.
• How to fix Error 15173: Revoke the permissions before dropping the login.
• How to fix error 15138 & Error 3729: DROP login failed

Microsoft SQL Server Error 15141

I had to remove a domain login on one of SQL Server instance where AlwaysOn is configured and running. Login was failed to drop because of Microsoft SQL Server error 15141 which suggests that this login owns one or more endpoints. Error details are given below:

Drop failed for Login “Login Name”
The server principal owns one or more endpoint(s) and cannot be dropped. (Microsoft SQL Server, Error:15141)

As error clearly says that one or more endpoints are owned by this login so let us check the details about endpoints. Run below T-SQL code to get the details of endpoint.

SELECT n.name, a.*  FROM sys.endpoints a
inner join sys.server_principals n on a.principal_id=n.principal_id
Go

You will see the endpoint details in below screenshot along with the login id who owns the endpoint. I have blured it because of privacy.

Solution

As we can see that endpoint is owned by this login so now we will change the owner of this endpoint to break the dependency which are the main reason behind this SQl Server error 15141. Now next step is to change the owner to some another login. You can also transfer the ownership to system account sa.

We will use ALTER Authorization statement to transfer ownership of this endpoint from existing server level login to some another server level login. We can not set the ownership to database level users. ALTER AUTHORIZATION can be used to change the ownership of any entity that has an owner. Run below command to change the owner of above endpoint to a login Domain\abc5.

--Replace the login id [Domain\abc5] with your login.
ALTER Authorization on endpoint::Hadr_endpoint to [Domain\abc5]
GO

We can see command executed successfully. You can recheck the ownership by executing same command which we have executed in first section. Once change is done. next step is to drop the login.

We can see, now ownership of this endpoint is set to another login. Next step is go ahead and drop the login again. you can do it by either SSMS or T-SQL. SSMS way is given below:

• Connect to target SQL Server Instance.
• Expand the security folder.
• Expand the Logins folder.
• Right click and choose delete on the identified login which needs to be deleted.
• Click on Ok button of the login deletion window.

If you want to drop this login using T-SQL command then open a query window and execute below command.

--change the name of Login_name with your login name which you want to delete.
DROP Login 'LOGIN_NAME'

This time your login will be dropped successfully. If you are still facing some another issue during dropping this login, you can read below articles where i have demonstrated step by step method to fix the DROP login failed errors:

• How to fix Error 15174: Login owns one or more databases.
• How to fix Error 15173: Revoke the permissions before dropping the login.
• How to fix error 15138 & Error 3729: DROP login failed

I hope you like this article. Please follow us on our facebook page and on Twitter handle to get latest updates.

The post Fix SQL Server Error 15141: The server principal owns one or more endpoint(s) and cannot be dropped appeared first on Techyaz.com.

Microsoft SQL Server Error 15138

I have discussed similar type of issue in my last tip, where a server level login was owner of some databases which causes to fail the login removal and throws error 15174. We changed the ownership and then tried to drop that login and it was successful.

Microsoft SQL Server Error 15138 which i am discussing in this tip is also similar kind of error. Here, user has owned some schemas at database level. We will do the same thing, we will change the owner of identified schema and drop the user.

The details of SQL Server error 15138 is given below.

As error clearly says that a schema is owned by this user in the database so let us check the schema that is owned by this user. Please follow the below process to check the owned schema for an user in the database.

• Connect to SQL Server Instance in SSMS.
• Expand the database folder followed by the actual database name in which your user exists or created.
• Expand Security folder inside your target database followed by the Users folder and double click on the target user which you want to drop.
• You can see a section named “Owned Schemas. Here you can see the schemas that are owned by this user.

If you find any schema that is owned by this user in above steps, you need to change the owner from this user to some other user or you can change it to dbo as well. See the below screenshot of the owned schema for a user.

Solution

Now we have identified the schema which is owned by this user. Our Next step is to change is owner of the identified schema and then drop the login.

 --Change DBName with your database name and Schema_Name with your schema name which is owned by this user.
USE [DBName] 
G0 
Alter Authorization ON Schema::[SCHEMA_NAME] TO [dbo] 
Go

Once above command will execute, next step is to drop the user again. Run below command to drop the user.

--Change DBName with your database name where user exists and USERNAME with user name which you want to drop.
USE [DBName] 
Go 
DROP USER USERNAME 
Go

This time it will work and user will drop from the database. You can also delete this user from SSMS by right click on the user and choose the delete option. SSMS way is given below:

• Connect to target SQL Server Instance.
• Expand Database folder in which user exists.
• Expand the Security folder and then Users folder to get the target user name.
• Right click and choose delete on the identified user which needs to be deleted.
• Click on Ok button of the user deletion window.

There are many reasons which causes to fail the user or login deletion. You can find many errors and their solutions in given links. Learn to fix:

• Error Code 15174: Login Owns one or more databases(s). Change the owner of database(s) before dropping the login.
• Error Code 15173: Revoke the permission(s) before dropping the login.

Microsoft SQL Server Error 3729

We have seen how to drop an user who was owner of a schema in above section. Now we will understand how to drop a schema that is referenced by an object. If you try to run DROP Schema statement and that particular schema is referenced to some object you will get below error. The details of SQL Server error 3729 is given below.

In order to fix this issue, we will change the schema of table “Locations” to remove the reference. We will use sp_changeobjectowner system stored procedure to change schema from abc to dbo. Run below command to change the schema of the table “Locations” from abc to dbo.

--Change DBName with your database name where user/schema/table exists
--Change the abc to your schema name.
USE DBName
GO
sp_changeobjectowner 'abc.Locations','dbo'

Now go ahead and drop the schema post executing above command. This time it will drop without an error.

--Change DBName with your database name where user/schema/table exists
--Change the abc to your schema name which you want to delete.
USE [DBName]
GO
DROP SCHEMA [abc]
GO

You can also drop the same using SSMS as well. Go to schema folder inside the security folder of your database. Right click on identified schema and choose delete option.  it will delete your schema.

Learn to fix below errors as well:

• Error Code 15174: Login Owns one or more databases(s). Change the owner of database(s) before dropping the login.
• Error Code 15173: Revoke the permission(s) before dropping the login.

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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