New User for CentOS VPS Created Using SSH

Create a New User CentOS Account on a VPS

A tutorial to add a user using SSH to access a CentOS VPS (the method applies to other Linux versions). In summary the steps are:

  1. Use useradd to add the new user.
  2. Use passwd to create the user’s password.
  3. Use visudo to make the user a sudoer.
  4. Login as the new user to test the sudo ability.

What’s Required for This Tutorial

The use of a Virtual Private Server (VPS) to run systems in the Cloud is a core aspect of modern computing (see What is a VPS?). Being able to access a VPS via a secure shell (SSH) is an essential skill. This tutorial shows how to add a new user to a VPS via SSH. It assumes that a VPS is installed and running and that a SSH client is available. It is recommended that a test system is used to become familiar with the process. This example uses a virtual machine (VM) running a minimal install of CentOS. The PuTTY program is used to access the CentOS VM.

To replicate this set up on a Windows machine follow these articles:

It is assumed that the live VPS system has a default operating system (OS) install. If a hosting company is providing the VPS they should have helpful documentation providing an overview of what is installed and how to access, configure and stop and start the VPS. Hopefully the default root superuser login has been given a strong password which was provided when the VPS account was obtained.

Security is a Top Priority

Once a VPS is up and running adding a new user account is one of the first tasks to do. For management purposes the default root user is not used for day-to-day (general administration) operations. This reduces the risk of inadvertent changes. A new user can be set up to do common administration tasks. The new user can temporarily elevate their privileges to perform the admin task. Note that not all users are given this ability. Only those who are trusted and need it for their work role.

Choosing Good User Names and Passwords

Do not use simple user names that are easily guessed, such as useradminguestdemotest etc. A combination of letters and numbers is better. For example someone called John Doe could have JDoe478 where the number part is the employee number, or John478DOE. The user name needs to be both easy to remember (for the user) but not immediately obvious (to help security). Notice the use of mix case to aid with the security.

A good password is a long string of random looking numbers, letters and punctuation. Words that can be found in dictionaries and common passwords such as password, 123456, letmein etc. are very poor. One way to generate a good password is to visualise a phrase that is personal and take the letter of each word of the phrase. For example: My mother lives at number 27 she likes squirrels’ fluffy tails. This produces Mmlan27slsft, which has mixed case and numbers and is of a reasonable length.

 Log in as root to Create the New User CentOS Account

Run a SSH client, here PuTTY is used on a Windows machine. Enter the appropriate IP address and port number for the VPS (on the test configuration it is localhost and 2222, on a live system it will be a valid IP address and likely port 22 for SSH).

If connecting for the first time an alert confirmation message will need to be accepted, select Yes to accept the message. Log in as root. Enter the root password and the prompt will be displayed.

Using PuTTY for SSH New User CentOS

Issue the useradd command with the required user name (the command adduser is a synonym for useradd). Note in this article a hash sigh, #, is used to indicate the end of the prompt line on the terminal. Type everything after the #.

# useradd JDoe478

Create the new users password with the passwd command, typing it twice.

# passwd JDoe478
Changing password for user JDoe478.
New password:
Retype new password:
passwd: all authentication tokens updated successfully

A warning is displayed if the password is considered weak. Run passwd again if required.

(To list users use cat /etc/passwd which shows the user names and other information, such as user id and group. Use cat /etc/passwd | cut -d “:” -f1 to list just the names. System defined users will be in the list.)

Add the New User CentOS Account to the Root Privileges

For the new user to be able to run admin commands, just like root, the sudoers configuration file must be update with the new user’s log in name. This is done with the visudo command.

# visudo

Move the cursor down to MACHINE=COMMANDS section. How the section is commented may vary between operating systems. For the CentOS 6.5 minimal version, used in this example, place the cursor just after:

## Allow root to run any commands anywhere
root    ALL=(ALL)    ALL

Press the a key to enter add (insert) mode. Duplicate the root line for the new user:

JDoe478    ALL=(ALL)    ALL

Thus the MACHINE=COMMANDS section will now have:

## Allow root to run any commands anywhere
root             ALL=(ALL)    ALL
JDoe478    ALL=(ALL)    ALL

Press the Escape key then enter the write and quit command with :wq (colon w q). The new user is now able to perform system administration commands.

Run a new PuTTY session to test the new user. The last character of the command line will be a $ to indicate a standard user.

Super User Do – sudo

Once logged in under the new account use the sudo command to run a privilege command. For example the visudo command was used by root to edit the sudoers configuration. Trying to run visudo under the new user will fail with Permission denied.

$ visudo
visudo: /etc/sudoers: Permission denied

As the new user, with root privileges, run visudo with sudo short for super user do:

$ sudo visudo

The password for the new user (not the root user) is requested. This is used to confirm the action to execute a root level command (and also log the action).

$ sudo visudo
[sudo] password for JDoe478

If you see:

visudo: /etc/sudoers: Permission denied

The password may be entered incorrectly. If a message starting with the user name and continuing with “is not allowed to run sudo on srv” is displayed. Check the above steps to ensure the user and sudoers configuration are set correctly. Sometimes the word ALL in the MACHINE=COMMANDS section is spelt incorrectly with lowercase l instead of uppercase L.

Another sudo example is the shutdown command. Run a restart command without sudo:

$ shutdown -r now
shutdown: Need to be root

And with sudo:

$ sudo shutdown -r now
[sudo] password for JDoe478:

Broadcast message from JDoe478@test.server
The system is going down for reboot NOW!

Remember that executing a root command using sudo requires the user to re-enter their password, ensuring confirmation of the command (and logging it in the system). To finish SSH sessions use logout or exit.

Summary on Configuring a New User in CentOS Via SSH

  • Use a SSH terminal client program to access the VPS.
  • Login as a user with root privileges.
  • Use useradd (or adduser) to add the new user (e.g. useradd JDoe478).
  • Use passwd to set the users password (e.g. passwd JDoe478).
  • Add the new user to the MACHINE=COMMAND section in the sudoers configuration file (e.g. JDoe478    ALL=(ALL)    ALL) with visudo.
  • When logged in under the new user use the sudo command to run root commands (e.g. sudo shutdown -r now).

How Many Websites Are There In The World?

And How Many Websites Are Active?

The Internet is BIG! Very big. However it is dominated by just a few hundred organisations and their websites. So how big is the Internet?

(Note this post first appeared in January 2014 and was updated in January 2015.)

The size of the Internet can be measured in various ways, including totals such as how many websites are there, how many domains are registered, how many websites are being used, what are the most popular web sites, how much storage is required to hold all the web data, how much data is transmitted, etc., etc. The trouble is the Internet is so big that these totals and numbers change all the time. For this brief look at the size of the Internet the total number of active sites is examined. In other words you can type a unique domain name into your browser’s address bar and you will get a response.

So let us look at the latest update on the size of the Internet according to the Netcraft January 2015 Web Server Survey. How many websites are there? There are 876,812,666 websites (over 876 million web sites). This is a slight rise on the number of websites compared to last year. In the Netcraft January 2014 Web Server Survey there were 861,379,152 websites. It is interesting to note that in September 2014 the total number of websites exceeded 1 billion. The number of web sites reached 1,028,932,208 in October before falling back below 900 million. Has the world got enough web sites now?

Those of you that don’t fully understand the workings of the Internet may not realise that this number is just over three times larger than the number of registered domains. Why?

What is the Total Number of Domains in the World?

According to the Verisign Domain Name Industry Brief the total number of registered domain names is 284 million, an increase over the January 2014 figure of 265 million. So 284 million domains support over 876 million websites. But not all registered domains get used. Some are just registered so that no one else can register them. Some are registered and never used.

When this post was first written in January 2014 the ZMap project, a high speed open source network scanner, had scanned the entire Internet and estimated the total number of hosts at 108 million. Then it was likely that the 861 million websites were active on 108 million hosts. This is because a domain can be divided into sub-domains. For example a blogging website, such as Blogger, WordPress or Ghost, will let a user create a website that hangs of the main domain name, e.g. http://googleblog.blogspot.co.uk.

The January 2015 Netcraft Survey reports just over 5 million (5,061,365) web facing computers. So 5 million computers run over 100 million hosts serving up 876 million web sites. Most of these sites are static and hardly change. Netcraft estimates that there are 177 million (177,127,427) active sites (those that get regular changes).

A Few Hundred Sites Dominate the Internet

Despite there being over 876 million websites only a few hundred dominate the Internet. Less than 1 million, or 0.1%, account for over 50% of web traffic. To get an idea on how much such a small percentage of the total websites dominate look at The Internet Map

The Internet Map shows relative web site sizes

or Icons of the Web.

Web site importance via Icons of the Web

The web site Alexa lists the top 500 websites.

Summary for How Many Websites Are There

As of January 2015:

  • There are 284 million registered domains…
  • on over 108 million hosts provided…
  • by 5 million computers serving…
  • over 876 million websites.

If you publish a web site it is very unlikely it will get noticed unless you are prepared to produce quality content, perform Search Engine Optimisation (SEO) and spend on marketing. Or you may get lucky and be the next big thing, as all the top sites were once.

Free Up Disk Space on Windows 8 with a Disk Cleanup

Disk Cleanup to Solve Low Disk Space Messages

Tips to free up disk space on Windows PCs, these disk cleanup pointers apply to the latest Windows versions, Windows 8.1, Windows 8 and Windows 7, also previous Windows versions, Windows Vista and Windows XP. With the use of Soild State Drives (SSDs) in new computers the amount of free disk space is generally lower than it used to be. This means that low disk space messages are more common. What types of messages will you see?

Low Disk Space and Similar Messages When The PC is Running

One day the PC is running OK, then out of the blue there are warning messages popping up. Sometimes these appear after installing a new program, or downloading a film from iTunes, or after a Windows Update. Sometimes the messages, or low disk space notifications, just start appearing for apparently no reason. Here are some of the typical messages that can be seen (and they usually come with a PC that starts running slower):

  • Low Disk Space.
  • Windows – Out of Virtual Memory.
  • Your system is low on virtual memory.
  • Your computer is low on memory.
  • Not enough storage is available to complete this operation.
  • There is not enough free disk space to run Steam.
  • There is not enough space to install these option(s).
  • There is not enough space on target drive while attempting to copy files.
  • There is not enough space on the disk.
  • There is not enough free disk space to extract the installation data.
  • There is not enough space on the Local Drive.
  • Close programs to prevent information loss.

What they generally mean (though not always) is that the PCs hard disk is nearly full up.If the hard disk gets completely full the computer will slow down and may not boot up correctly on next use. You may need to use a Windows boot disk or recovery disc to boot the system and free up some space.

Perform a Disk Cleanup to Free Up Disk Space

There are several disk cleanup task that can be performed. Once done the hard disk with be OK for a short while. However, a longer term solution will be required. Sometimes just reorganising the layout of the computers files will sort the issue. Sometimes it will be worth adding a new hard disk to reduce the problem in the future.

Accessing Control Panel in Windows 8.1 and Earlier Windows Versions

You will also need to access the computer’s Control Panel. On Windows 8 or Windows 8.1 at the Start screen start typing con and Control Panel will be listed for selection (or use the context menu, usually right click, on the Start flag and select Control Panel, alternatively hole the Windows key and press X then select Control Panel from the menu.) In Windows 7 and earlier access Control Panel via the Start button.

Use the Administrator Account for a Disk Cleanup

Let’s start the disk cleanup, You need to be logged on as a Computer Administrator to perform many of these cleanup tasks. If several users have accounts on the computer log in with one that is set up as a Computer Administrator (usually the first account created when the computer was first set up).

Empty the Recycle Bin

If there are items in the Recycle Bin on the desktop empty it. Look at the Recycle Bin icon on the desktop and if it looks like it has paper in it then it has items in it. Bring up Recycle Bin’s context menu (usually right-click) and select Empty Recycle Bin. A message may be displayed to confirm the permanent deletion. If required open the Recycle Bin (double-click) to check the contents.

Delete the Contents of the Windows Temporary Folder

Computer software, such as installers, apps and other programs will sometimes generate temporary files when running. Once the files are finished with they should be deleted by the software that generated them. Sometimes they don’t get deleted or the software crashes before the temporary files are deleted. If the software generated the files in the correct temporary location, either C:\Windows\Temp or in the logged on users AppData area (\AppData\Local\Temp), then these directories can be emptied.

(Sometimes the temporary directories are moved. To check their location view the systems environment variables. In Control Panel open System and Security select Advanced system settings. On the Advanced tab select Environment Variables. The location for temporary files is stored in the TEMP and TMP variables for the user and the system. TEMP and TMP normally point to the same place but can be set differently. User and system TEMP/TMP are normally different but again can be set to the same location.)

Close any running programs before cleaning the temporary directories. Using Windows File Explorer go to C:\Windows\Temp (or the location determined by the TEMP/TMP system environment variables). You may need to turn on Hidden items in Explorer using the View menu. Delete the all the contents of C:\Windows\Temp (you may need to give permission to do so). Some files and directories will not delete if programs or services are still using them.

Open the logged on users data folder. Either through C:\Users (e,g, C:\Users\John Doe for a user named John Doe) or the desktop with have a folder icon named after the user. Again with Hidden items enabled in Explorer browse to AppData\Local\Temp (or the location determined by the TEMP/TMP user environment variables). Delete all the contents. Again some may fail to delete because they are still in use.

If the computer has another hard disk with plenty of free space the TEMP and TMP directories can be changed to use the different disk. Change the TEMP/TMP user and system environment variables settings to a location on the other disk. E.g. create a TEMP directory on another hard disk, change the TEMP and TMP variables in Control Panel to point to the new directory. So if created on a D: drive it would be changed to D:\TEMP. Restart the computer for the change to take effect. Programs will use the new location for temporary files.

(Warning: A few programs will still use the default TEMP/TMP locations because of hard coded settings, including some Microsoft installers. So don’t forget to clear the C:\Windows\Temp and the user’s AppData\Local\Temp directories occasionally.)

Clear Web Caches and Move Them to Another Drive

For all the installed web browsers clear their caches. If the PC has another hard drive the cache locations can be moved to the other drive to help prevent low disk space issues in the future. The article Clear Web Cache and Moving Browser Cache Folder shows how to delete the web cache for Internet Explorer, Google Chrome, Mozilla Firefox and Opera.

Remove Unused Programs and Bloatware (Manufacturer Install Software)

Open Control Panel and under Programs select Uninstall Program. For each program no longer, or never, used select it and select Uninstall. Only remove programs you are sure about as some will be needed by the system and some used by other programs. Research the program on line if unsure. If in doubt leave it installed.

Turn Off Windows Features

Again using Programs in Control Panel select Turn Windows features on or off. Uncheck anything not used, however, it is likely that only advanced users will know what features can be turned off. Research on line if unsure and if in doubt don’t change the settings.

Delete Old Folders, Documents, Photos, Videos and Music

Using Windows Media Player, or your chosen media player (e.g. iTunes), to delete any media no longer required. Use Windows File Explorer to view the contents of the logged on users files. Delete any item (folders and files) no longer required.

Clear Out the Offline Email

If you email is stored on the computer and not the server then browse all the items and delete anything not required. Do this in the email program.

Remove Old Users and Their Files

You will need to be logged in as a Computer Administrator to delete other user accounts. Make sure any data stored under old user accounts is no longer required (if so copy it to another account or to offline storage).

In Control Panel under User Accounts and Family Safety select Add or remove user accounts. Select the account to remove. Click Delete the account. When asked if files should be kept select Delete Files to recover the space used by the account. Select Delete Account to confirm. The user account and all its files are removed.

Ensure Windows is Up To Date

Windows is updated regularly to improve security and reliability. This update process uses and creates temporary files. To delete these files first make sure all the latest updates have been installed. Otherwise updates that have been downloaded but not installed may be removed during the clean up process. (If this occurs they will be downloaded again at the next update.)

In Windows 7 use Windows Update via Start and All Programs. In Windows 8 type Settings at the Start screen and select PC Settings, then Update and Recovery. (Or in Control Panel enter Update in the search box and select Windows Update.)

Select Check for updates or Check now to ensure that “No updates are available”. Otherwise Install Updates. The Windows Update may fail if there is not enough space to install the update. Sometimes installing updates one-by-one (oldest first) can overcome update errors. Otherwise finish this list of disk cleanup tips and then try performing Windows Update again.

Run the Disk Cleanup Program

Free Disc Space Using Windows Disk Cleanup Advanced OptionsWindows comes with a Disk Cleanup utility that is automatically run once in a while. However, it can be run to clean up additional system files. Start Disk Cleanup by selecting it via Start, All Programs, Accessories and System Tools. On Window 8 type Disk at the Start screen and select the option that starts Clear Disk Space…

Note that when Disk Cleanup is performing the work it can take some time to complete. You may need to plan to leave it running for quite a while.

Select the drive to clean up, i.e. the one low on space. It will do a scan to determine files to cleanup. When the Disk Cleanup dialog displays select the Clean up system files button. Select the drive again and another scan is performed. Now a More Options tab is available. On the More Options tab select Clean up in the System Restore and Shadow Copies area. Confirm deletion of all but the last restore point by selecting Delete to the displayed question.

Click the OK button to perform the clean up of the items listed on the Disk Cleanup tab.

Sometimes the Disk Cleanup utility can appear to hang. It after a few hours it has not completed restart the computer. Continue with the remainder of these tips and return to Disk Cleanup after the other steps have been completed.

Run a Cleanup Utility

A dedicated third party cleaner, such as Piriform’s CCleaner (Computer Cleaner), will detect other files to clear. Running a utility like CCleaner can help remove unwanted files.

Clear the SoftwareDistribution Download Folder

If Windows Update is complete (see the Ensure Windows is Up to Date section earlier). Some of the files used by Windows Update but no longer required may still be left around. These can be removed to free up disk space. This is covered in the separate article SoftwareDistribution Folder Delete in Windows.

Clear the Prefetch Folder

Every time Windows starts, every time the same program is run, Windows loads the same program files again and again. Knowing this Windows bundles those files together in a cache called the Prefetch Folder. This folder is updated automatically by Windows. However, if disk space is really tight, and you have removed some recently used programs, you may free a little more space by deleting the contents of Prefetch. Windows will recreate the Pretch folder when the computer next runs. The small downside to deleting the contents of the Prefetch folder is that Windows start up and the running of some software will be slower than normal until the new Prefetch files have been automatically recreated.

To delete the contents of the Prefetch folder open up Windows Explorer, click on the Windows directory (normally C:\Windows). Find the Prefetch folder (C:\Windows\Prefetch). Select all the files in the folder (use Ctrl-A) and press delete. Restart the computer. (New prefetch files will be created as the computer is used). Windows automatically manages the Prefetch folder so clearing it is only required if disk space is extremely low.

Delete System Dump Files and Change the Creation Location

Windows can crash because of a hardware or software fault, or loss of power. When this happens Windows can create dump files that may be sent to Microsoft (to help diagnose faults). A dump file is literally a “dump” of the state of computer at the time of the crash. There can be a MEMORY.DMP file in C:\Windows and in C:\Windows\Minidump a series of dump files for each crash that occurs (if Windows got the chance to create the file). Note that depending upon dump settings and the nature of the crash either MEMORY.DMP or the mini-dump files may or may not be created.

If you do not need to analyse the cause of a crash the dump files can be deleted (if not already deleted by Disk Cleanup or a third party cleaning tool). Using Windows Explorer see if MEMORY.DMP is in C:\Windows and if so delete it. Go to C:\Windows\Minidump. and select all the files and press delete.

If required the location that the dump files are created can be changed. If space on the system disk is tight move the location to a disk that has more space. In fact MEMORY.DMP will not be created if the system disk is low on space. If this is the case and the PC is crashing often then change the dump file location. This will give the opportunity for analysis of the dump file at a later date.

Use Control Panel to open System and Security and select System. For the left hand list select Advanced system settings. On the Advanced tab under Start-up and Recovery select the Settings button. On the Start-up and Recovery dialog change the dump file location in the Write debugging information section. E.g. if a D:\TEMP directory existed on a machine (and the D: drive had lots of free space) the Kernel memory dump could be changed from %SystemRoot%\MEMORY.DMP to D:\TEMP\MEMORY.DMP. Restart the computer if changes are made.

Move Personal Folders to Another Drive

The personal folders of the PC’s users are on the same drive as Windows by default. For PCs with multiple drives the personal folders (Documents, Music, Video etc.) can be moved to a hard disk with more room. The process is easily done with Windows Explorer. With Windows Explorer open locate the personal folder for the logged on user (e.g. Documents, Music, Pictures etc.), open the context menu (usually right-click). Select Properties. On the Location tab enter the new location (on a different hard drive with plenty of space) and click OK. Select to confirm creation of the new location and select Yes to confirm moving of the files. Full details on moving personal folders is in the article Move My Documents and Other Personal Folders in Windows 8.1, 8 and 7.

Move the Page File

A powerful PC may have 8GB or 16GB or RAM (memory). Less powerful computers may use a disk file call the Page File to simulate more memory, known as virtual memory. The page file (pagefile.sys) is on the system drive by default. If the computer has another drive (and if it is a faster drive) the page file can be moved to another drive. This can save space on the system drive. To change the page file location use the Advanced systems settings (in Control Panel open System and Security and select System. For the left hand list select Advanced system settings.) On the Advanced tab under Performance select the Settings button. Select the Advanced tab on the Performance Options dialogIn the Virtual Memory section select the Change button.

On the Virtual Memory dialog select a hard drive with free space, ideally the fastest drive in the system. (Uncheck the Automatically manage paging file size for all drives.) With the required drive selected choose the System managed size option (Windows sizes the page file as required). Click OK to close the dialog boxes, a system reboot will be required.

Move Installed Programs

If programs are no longer required they can be removed. For programs that are still used, and the install media is still available (or can be obtain via an Internet download), they can be re-installed. When re-installed instead of selecting the normal install location of C:\Program Files or C:\Program Files (x86) choose a drive with plenty of space and create a programs directory on it. E.g. D:\Programs. When a software installer runs some of them allow the install location to be selected (sometimes directly or via a Customize button). Change the install directory to a sub-directory in the new Programs directory (you may have chosen a different name for the alternative programs directory).

Run a Cleanup Utility Again

After performing the above clean up tips run a third party clean up tool again. It may find other items that can be deleted (e.g. files left over when a program is moved to a new drive).

Defragment the Drive (Does not Apply to Solid State Drives)

A hard drive is made of many thousands of sectors. When files are saved to a hard drive they are saved into the sectors. Sometimes the free sectors are next to each other. Some times they are spread out. This means a file can also be spread out. A sector may not be fully used up by a file as well. This means a drive may have lots of sectors with parts of files and lots of sectors partially filled with parts of files. This is known as fragmentation. A defragmentation utility will rearrange files and parts of files to use the sectors more efficiently. This can free some disk space. This does not apply to Solid State Drives (SSDs) as they use a different technology to store data.

On Windows defragmentation is done automatically at regular intervals. However, sometimes it needs to be run manually. In Windows 8 from the Start screen start typing defrag then select the Defragment and optimise your drives option. In Windows 7 from the Start button select All Programs then Accessories and the System Tools. Select the Disk Defragmenter utility.

Use a Third Party Defragmentation Utility

There are different defragmentation algorithms. Therefore a different defragmentation utility may free up a little more space. Try one if necessary, such as the Piriform Defraggler.

Install a New Disk

If a lot of the above steps could not be completed, because there is only one disk drive in the machine, consider adding a new hard disk. There are lots of tutorials on line showing how to add a hard disk to a computer, alternative someone you know can probably help or knows of someone to help you install a new disk. Adding another hard disk is reasonably easy. Once another disk has been added run through the above list again.

Turn of Windows Hibernation and Delete the Hibernation File

Windows supports a hibernation mode, the system can restart quicker from a power off state if hibernated. To do so the running configuration is stored in a file C:\hiberfil.sys. This can be almost as large as the amount of memory the machine has (e.g. 8 GB). If all the clean up options have been tried and space is still needed turning off hibernation and removing the hiberfil.sys file can free up desperately needed space. This is done via an administrators command prompt with powercfg.exe -h off. See the article hiberfil.sys Windows 8.1 Delete to Free Up SSD Space for full details.

Reformat the Hard Drive and Re-install the Operating System

This is probably the last resort step. Before resetting the PC with a fresh install of the operating system make sure any pictures, files or documents that must be kept have been copied to another location. An on line drive such as SkyDrive, Google Drive or Dropbox helps in this situation. Again if not sure how to do this find someone who can help or research on line.

Running low or running out of disk space can cause a PC to grind to a halt. However, by performing a disc clean up to free up disk space normal service can be resumed. This article has provided a few tips on how to achieve that.