Apache Virtual Hosts are great because they let you host multiple websites on the same server. The public IP address can also be re-used - Apache knows, based on the HTTP host header, which website to show.

But have you considered this scenario? website1.com gets compromised and some malicious person has access to the server. What can they do? Most certainly they have access to every other website on the server because, by default, every Virtual Host runs under the same user www-data. Fortunately, there is a module that allows us to use different users for every Apache2 Virtual Host called apache2-mpm-itk.

It is very easy to install:

apt-get install libapache2-mpm-itk

a2enmod mpm_itk

If you face any issues, disable mpm-prefork and try enabling mpm_itk again.

a2dismod mpm_prefork

Now, in the Virtual Host config file, insert these lines (user www-site1 and group www-site1):

<IfModule mpm_itk_module>
AssignUserId www-site1 www-site1
</IfModule>

The user could be added with useradd:

useradd www-site1

Lastly, give owner rights to the new user and no one else.

chown www-site1:www-site1 -R /var/www/site1

Or even better, give the www-site user write rights on the upload folder. Everything else is readable only.

find /var/www/site1/ -type d -exec chmod 0755 {} \; #Change directory permissions rwxr-xr-x

find /var/www/site1/ -type f -exec chmod 0644 {} \; #Change file permissions rwxr-xr-x

chown ajni:ajni -R /var/www/site1/ # Let your useraccount be owner

chown www-site1:www-site1 -R /var/www/site1/uploads/ #Let apache be owner of upload folder

Oh yeah. Don't forget to restart apache:

service apache2 restart

References:

https://cloudkul.com/blog/apache-virtual-hosting-with-different-users/

If you are using Citrix MCS with Azure VMs, you might have noticed that not all the VM SKUs are available to select when creating a new Machine Catalog. With PowerShell, though, you can use any Azure VM SKUs.

If you are using Citrix Cloud, you have to download and install the Citrix Powershell SDK and login with your Citrix credentials. Optionally you could download an API client and authenticate with those credentials.

The secure client can be downloaded under Identity and Access Management > API Access > Create client. The customer id will also be shown on that page.

You authenticate with the API client this way:

Set-XDCredentials -CustomerId "customername" -SecureClientFile "C:\temp\secureclient.csv" -ProfileType CloudAPI

Otherwise, without API credentials, after executing the first command, you will be asked to insert your Citrix credentials:

Now the commands to change the Citrix MCS VM type.

Get-ProvScheme -ProvisioningSchemeName "CatalogName"

Take note of the folder name after XDHYP:\HostingUnits\ under MasterImageVM.

This command will register the virtual drive XDHYP:\ in PowerShell:

Set-HypAdminConnection

Insert that folder name in this command:

Set-ProvScheme –ProvisioningSchemeName "CatalogName" –ServiceOffering "XDHyp:\HostingUnits\Foldername\serviceoffering.folder\Standard_NV4as_v4.serviceoffering"

Delete and re-create the VM. The right VM type will be then used.

Normally, adding an Availability Set after the VM has been deployed is not possible. You would have to delete the VM, leaving the NIC and OS disk intact and then re-creating the VM with the Availability Set. Of course that can be done manually, but there is a PowerShell script that does this all for us.

This can be all done in the Azure Cloud Shell, you do not have to install the PowerShell Module on a Windows Machine.

Install-Module AzureRm.AvailabilitySetManagement

Create an AS before adding the VM to the AS.

New-AzureRmAvailabilitySet -Location "West Europe" -Name "myAs" -ResourceGroupName "myRg" -Sku aligned -PlatformFaultDomainCount 3 -PlatformUpdateDomainCount 5

Now add the VM to the AS:

Add-AzureRmAvSetVmToAvailabilitySet -ResourceGroupName "myRg" -VMName "VM01" -OsType windows -AvailabilitySet "myAs"

This will stop the VM if it is running, delete the VM item (leaving the NIC and OS disk intact) and re-create that with the same VM size inside the newly created Availability Set.

References:

https://pixelrobots.co.uk/2018/02/add-existing-virtual-machine-availability-set-azure/

https://gist.github.com/PixelRobots/3c34027d225c7acb09833840b7258ee9#file-movevmavaset-ps1

A while ago I made a blog post about Differencing Disks in Hyper-V. If you mainly work with Hyper-V, you should check it out: https://www.ajni.it/2019/10/hyper-v-create-a-master-vhdx-to-save-tons-of-space/. VMware Workstation utilizes a similar concept, called Linked Clones.

Linked Clones use a read-only disk as a reference, changes made to the VM are written into a separate writable disk. This technique allows us to save disk space and create a lot of VMs. Changes, at least in the beginning after the OS installation, are very small.

Install Windows 10 or Windows Server along with VMware Tools and then Sysprep your VM.

Now the template can be "cloned"

In VMware, a Differencing Disk is called Linked Clone. Just like in a snapshot, a linked clone uses a base read-only disk and saves changes into second, writable disk.

Now a name for the new VM can be inserted.

After booting up the new VM, we can see that the writable disk only consumes 7MB. 4GB are used for the memory state.

This feature is awesome for home labs. You can create multiple VMs off of that single base disk. In a lab, changes are usually very small, so you can save a ton of space using this method. I would not recommend updating your system through Windows Updates or enabling Bitlocker.

If for some reason the base disk is corrupt or lost though, every VM will be affected.

Server Core Edition is very lightweight, needs less Windows Updates, less disk space, and should be used whenever possible. Basic features like AD DS, DNS, DHCP, or IIS are supported on Server Core. Administering is also very easy once it is a member of the domain because it can be added to Server Manager on a server with GUI. We are installing AD DS in this article.

You can relatively easily change system settings on Server Core with the sconfig cmd tool.

sconfig

First change the server's name (Option 2).

Afterwards set the IP address to a static one along with DNS servers (option 8).

Return to the main menu and perform the Domain Join (option 1).

We don't need to change the computer name. The server will be then rebooted.

From now on, the fastest and simplest approach of administering your Windows Server Core is through Server Manager on a Server with GUI.

Add Roles and Features and promote the server to a Domain Controller. These steps are very straightforward. Some screenshots might be missing. If you want the step by step instructions, check out this post https://www.ajni.it/2019/10/server-2019-installing-your-first-domain-controller-in-a-new-domain/.

You can double check in Active Directory Users and Computers and Active Directory Sites and Services.

NTDS settings might not be created right away. Don't panic, this might take some time. You shouldn't create the entries manually.