The Microsoft Azure landscape is changing drastically and it's doing a good job of moving resource management to a more modern view. Coupled with Microsoft's security initiatives (Intune, Defender, Sentinel, Copilots for Security), Azure ARC is a great way of managing on-prem servers for updates.

Microsoft has a few ways of enrolling on-prem machines into ARC, but it's tedious to do this without bulk enrolment. Currently they support Config Manager, Group Policy or Ansible bulk enrolment. There is a Powershell option, but I guess it's meant as a starting point for devs as it doesn't actually do much. Let's fix it and have it remote install via Powershell to domain joined machines.

Follow the initial steps of creating the subscription, resource group and service principal. Grab the latest "Basic Script" ie Powershell (as the below might be out of date) and wrap it around some Invoke-Command. Replace the values in <> that come from your script that it generates for you. 

# Read machine names from CSV file
$machineNames = Import-Csv -Path "arc_machines.csv" | Select-Object -ExpandProperty MachineName
$credential = (Get-Credential)

# Iterate through each machine
foreach ($machineName in $machineNames) {
    try {
        # Invoke-Command to run commands in an elevated context on the remote machine
        Write-Host "Attempting to install on $machineName"
        Invoke-Command -ComputerName $machineName -Credential $credential -ScriptBlock {
            # Code to execute on the remote machine
            $ServicePrincipalId="";
            $ServicePrincipalClientSecret="";
    
            $env:SUBSCRIPTION_ID = "";
            $env:RESOURCE_GROUP = "";
            $env:TENANT_ID = "";
            $env:LOCATION = "";
            $env:AUTH_TYPE = "principal";
            $env:CORRELATION_ID = "";
            $env:CLOUD = "AzureCloud";

            [Net.ServicePointManager]::SecurityProtocol = [Net.ServicePointManager]::SecurityProtocol -bor 3072;

            # Download the installation package
            Invoke-WebRequest -UseBasicParsing -Uri "https://aka.ms/azcmagent-windows" -TimeoutSec 30 -OutFile "$env:TEMP\install_windows_azcmagent.ps1";

            # Install the hybrid agent
            & "$env:TEMP\install_windows_azcmagent.ps1";
            if ($LASTEXITCODE -ne 0) { exit 1; }

            # Run connect command
            & "$env:ProgramW6432\AzureConnectedMachineAgent\azcmagent.exe" connect --service-principal-id "$ServicePrincipalId" --service-principal-secret "$ServicePrincipalClientSecret" --resource-group "$env:RESOURCE_GROUP" --tenant-id "$env:TENANT_ID" --location "$env:LOCATION" --subscription-id "$env:SUBSCRIPTION_ID" --cloud "$env:CLOUD" --correlation-id "$env:CORRELATION_ID";
        }
    }
    catch {
        Write-Host "Error occurred while connecting to $machineName : $_" -ForegroundColor Red
    }
}

Next create the file arc_machines.csv with one column called MachineName and each row being the DNS/NETBIOS name of the machine you want to remote into. The script will ask for your domain creds when starting which will be used to Invoke-Command into the remote host. It'll then use the Service Principal to enroll the machine into ARC.

Ubiquiti Unifi OS devices now restrict updates to its own platform when it thinks a disk is unhealthy. This is the most pointless and infuriating UX change the Ubiquiti has made (and they've made a few terrible changes in the past).

At-risk disks are flagged:

• Bad sectors being reported on the disk
• Uncorrectable disk errors detected
• Failures reported in the disk’s Self-Monitoring, Analysis and Reporting Technology system (SMART)
• The disk has reached 70% of the manufacturer’s recommended read and write lifespan (SSDs)

To not allow updates to their own platform stagnates feature development, bug fixes and security enhancements. Sure, make the admin aware that they have an at-risk disk, but don't prevent them from getting your latest updates, that's just purposefully punishing your customers over things that are not their fault.

In my case, my disk was old, but still healthy. I am not sure whether the power on hours were a flag from SMART or maybe the temperature went over some arbitrary threshold they decided to implement.

I was able to work around this by manually upgrading the platform.

• Enable SSH on the controller
• Use the ubnt-systool and associated FW links as documented here: https://help.ui.com/hc/en-us/articles/204910064-UniFi-Advanced-Updating-Techniques
• Reboot and enjoy

If you don't want to pay for a Proxmox subscription you can still get updates through the no-subscription channel.

cd /etc/apt/sources.list.d
cp pve-enterprise.list pve-no-subscription.list
nano pve-no-subscription.list

Edit the pve-no-subscription.list to the below

deb http://download.proxmox.com/debian/pve bookworm pve-no-subscription

Run updates, but only use dist-upgrade and not regular upgrade as it may break dependencies.

apt-get update
apt-get dist-upgrade

I have a project where I routinely build and rebuild containers between two repos, in which one of the docker build steps pulls the latest compiled code from the others repo. When doing this, the Docker cache gets in the way as it caches the published code. 

For example:

• Project 1 publishes compiled code to blob storage
• Project 2 pulls the compiled code and publishes a built container

Project 2's Dockerfile will look something like:

FROM ubuntu:22.04
RUN wget https://blob.core.windows.net/version-1.zip
RUN unzip /var/www/version-1.zip -d /var/www/

The issue is if I update the content of version-1.zip, Docker will cache this content in its build process and be out of date. 

I came across a great solution on stackoverflow: https://stackoverflow.com/questions/35134713/disable-cache-for-specific-run-commands

This solution doesn't work completely for me, as I am using docker-compose up commands, not docker-compose build. However, after a little trial and error, I have the below workflow working:

FROM ubuntu:22.04
ARG CACHEBUST=1
RUN wget https://blob.core.windows.net/version-1.zip
RUN unzip /var/www/version-1.zip -d /var/www/

Run a build:

docker compose -f "docker-compose.yml" build --build-arg CACHEBUST=someuniquekey

Run an up:

docker compose -f "docker-compose.yml" up -d --build

This way the first run Docker build is cache busted using whatever unique key you want, and the second Docker up uses the newly compiled cache. NOTE: you can omit the last --build to not trigger a new cached build if you like. Now I can selectively bust out of the cache at a particular step, which in a long Dockerfile, can save heaps of time. I guess you could even put multiple args at strategic places along your Dockerfile and be able to trigger a bust where it makes most sense.

du -shc * | sort -rh

WSL is fantastic for allowing devs and engineers to mix and match environments and toolsets. It's saved me many times having to maintain VM's specifically for different environments and versions of software. Microsoft are doing a pretty good job these days at updating it to support new features and bug fixes, however, running WSL and Docker as a permanent part of your workflow it's not without it's flaws.

This post will be added to as I remember optimizations that I have used in the past, however, all of them are specific to running Linux images and containers, not Windows.

Keep the WSL Kernel up to date

Make sure to keep the WSL Kernel up to date to take advantage of all the fixes Microsoft push.

wsl --update

Preventing Docker memory hog

I routinely work from a system with 16GB of RAM and running a few docker images would chew all available memory through the WSL vmmem process which would in turn lock my machine. The best workaround I could find for this was to set an upper limit for WSL memory consumption. You can do this through editing the .wslconfig file in your Users directory.

[wsl2]
memory=3GB   # Limits VM memory in WSL 2 up to 3GB
processors=2 # Makes the WSL 2 VM use two virtual processors

You will need to reboot WSL for this to take effect.

wsl --shutdown

NOTE: half memory sizes don't seem to work, I tried 3.5GB and it just let it run max RAM on the system.

Slow filesystem access rates

When performing any sort of intensive file actions to files hosted in Windows but accessed through WSL you'll notice it's incredibly slow. There are a lot of open cases about this on the WSL GitHub repo, but the underlying issue is how the filesystem is "mounted" between the Windows and WSL. 

• https://github.com/microsoft/WSL/issues/4197

This bug is incredibly frustrating when working with containers that host nginx or Apache as page load times are in the multiple seconds irrespective of local or server caching. The best way around this issue is not have filesystem served from Windows, but serve it inside of the WSL distro. This used to be incredibly finicky to achieve but is easy now given the integration of tooling to WSL.

For example, say you have a single container that serves web content through Apache and that your development workflow means you have to modify the web content and see changes in realtime (ie React, Vue, webpack etc). Instead of building the docker container with files sourced from a windows directory, move the files to the WSL Linux filesystem (clone your Repo in Linux if you're working on committed files), then from the Linux commandline issue your build. Through the WSL2/Docker integration, the Docker socket will let you build inside of Linux using the Linux filesystem but run the container natively on your Windows host.

To edit your files inside the container, you can run VS Code from your Linux commandline which through the Code/WSL integration will let you edit your Linux filesystem.

Mounting into Linux FS

Keep in mind that if you do need to mount from Windows into your Linux filesystem for whatever reason you can do it via a private share that is automatically exposed.

\\wsl$

If you have multiple distros installed they will be in their own directory under that root.

Tuning the Docker vhdx

Optimize-VHD -Path $Env:LOCALAPPDATA\Docker\wsl\data\ext4.vhdx -Mode Full

This command didn't do much for me. It took about 10minutes to run and only reduced my vhdx from 71.4GB to 70.2GB.

Error not binding port

I've had this recurring error every so often when restarting Windows and running Docker with WSL2. Every so often Docker compains it can't bind to a port that I need (like MySQL). Hunting down the cause of this is interesting - https://github.com/docker/for-win/issues/3171 - https://github.com/microsoft/WSL/issues/5306

The quick fix to this is:

net stop winnat
net start winnat

Sometimes even in the most organised of worlds, we still manage to miss patching older systems. I found an old HP iLO server running iLO 4 - 1.20 with no way to log into it. Every modern browser and OS has now deprecated old TLS, RC4 and 3DES cyphers for certificates with the most common FF error being thrown: SSL_ERROR_NO_CYPHER_OVERLAP.

Irrespective of what I tried (such as security.tls.version.min, version.fallback-limit, IE compatibility modes) nothing would work. Even an old 2008 server running IE wouldn't work because of Javascript blocking etc. Unfortunately the only way I could work around this was to spin a Win7 machine running original IE to bust into it. Ideally I wouldn't have had to roll a new Win7 VM, but old versions for this reason should be in everyones toolbox.

Once in, it's easy enough to upgrade to a more modern iLO FW which supports modern TLS considering that HP make it readily available https://support.hpe.com/connect/s/softwaredetails?language=en_US&softwareId=MTX_729b6d22f37f4f229dfccbc3a9.

This is the computed list of SSH bruteforce IP’s and commonly used usernames for April 2013.

Top 50 SSH bruteforce offenders IP’s.

Top 50 SSH bruteforce usernames.

I maintain a radius server that proxies requests from publicly accessible SSH servers which, unfortunately must run on port 22.

There are over 140 SSH servers that proxy all requests through this server and due to the logging which is configured I am able to capture all failed attempts including username password and IP address. I frequently scan these logs to find the top offending IP addresses and common usernames so I can add them to a blacklist for the radius server to drop straight away.

There are many public projects that compile sources of such information, however these logs are easy for me to divulge for others to incorporate into similar lists.

I will throw some old stats of interest and work on this to become a monthly release.

October 2012
Failed Attacks: 19,969,074

November 2012
Failed Attacks: 11,335,220

December 2012
Failed Attacks: 5,277,817 <- I guess everyone went quite over the holiday period?

January 2013
Failed Attacks: 6,786,138

February 2013
Failed Attacks: 17,375,929

March 2013
Failed Attacks: 16,437,020

April 2013
Failed Attacks: 5,542,223

May 2013
Failed Attacks To Date: 3,347,659