I've had a pihole on my home network for years. I set it up on a pi3b natively and it ticked along doing its thing, until it didn't. The sd card wore out and became read-only. It took me a while to discover that that was the issue, as it still worked, but you couldn't make any changes. Well, you could - everything seemed to work, but nothing was actually being written. Fortunately I had a teleporter backup of the pihole. I quickly spun up a vm with a pihole docker instance and loaded the data from backup. I then pointed all the machines at the new IP ¹. In the mean time, I ordered m2 sata SSDs and USB enclosures, and worked out how to get my two raspberry pi's to boot off a USB attached SSD.²

When I re-setup the pi on the new SSD, I decided that the convenience and ease of the docker setup was ideal. I ran both instances of pihole but kept them separate initially. I eventually found a script to sync the piholes via git. At a later date, I found gravity-sync, which is just brilliant.

I configured all my hosts to use the pi as primary dns, and the pihole vm as secondary. This worked brilliantly until a few months later, I noticed a weird issue where internet access seemed a bit slow. It took a short while to open up an initial connection to a site, but after that things were fine. Investigating, I discovered the pi wasn't responding to ping. The SSD had died. I RMA'd the SSD and ordered a replacement. They're fairly cheap and the RMA process will take a while. In the mean time, I configured everything in the network to point to the pihole vm as primary.

While waiting for the new SSD to arrive, I was thinking about load balancing. Previously, the pi was answering queries from most of the user devices, while the vm was answering queries mostly for my internal servers/services. NGINX could do the load balancing and I was already using a few instances for various things, and I am also using Nginx Proxy Manager to handle just about everything. I figured I could probably use it to do the balancing as well.

You can't use Nginx Proxy Manager to do load balancing. Yet³. Their interface doesn't allow for it.⁴

I set up a new nginx docker instance using the official alpine slim container, as I'm only going to use it for load balancing, I don't need bells and whistles. The image is ~11mb. I created a file called stream.conf and included it in nginx.conf.

stream.conf:

stream {
        upstream dns_servers {
                random;
                server 192.168.0.2:53;
                server 192.168.0.3:53;
        }
        server {
                listen 53;
                proxy_pass dns_servers;
        }
        server {
                listen 53 udp;
                proxy_pass dns_servers;
        }
}

I also made sure to pass port 53 tcp & udp to docker.

I've now configured the load balancer as primary DNS, with one of the pihole instances as secondary ⁵ So far it's working really well. I did notice some delays here and there, but I solved that, see footnote ⁴.

One drawback of this method is that the piholes only see queries coming from the load balancer, they don't see the actual source of the query. This is not a huge issue for me. I've also configured my firewall to capture direct external DNS query attempts and redirect them to the load balancer with some source and destination NAT thrown in.

Photo by Christophe Hautier on Unsplash

Ultimately this is related to setting up MainsailOS for use with my modified 3D printer (Creality CR6-SE).¹

I had a Pi4B 8Gb running Home Assistant OS on an m1 sata SSD in a USB enclosure, which I had no issues with whatsoever, however all my intentions for Home Assistant haven't materialized, so I figured I'd get more use out of it if I switched to running Klipper on it. Ultimately I decided on using Mainsail via their MainSailOS raspberry pi image.

Considering that the Home Assistant OS installation on the SSD was easy enough via Raspberry Pi Imager when I decided to convert from using an SD Card to using an SSD, and since Mainsail OS is available via RPI Imager, I figured it would be easy to just write the image to the SSD and off I go.

It was not to be. ²

After allowing some time for the system to boot and resize the partition, I was still unable to ping the device's IP (set via static DHCP). I connected a screen and keyboard to the pi and restarted it (as it was headless it had not initialized the display). The system started booting, then complained about disk corruption. It also threw a kernel panic. Some boots it would attempt to do the partition resizing but then complain of missing partitions. But it usually ended up with a kernel panic.

I connected the SSD to my desktop, cleared the partitions, created a windows partition then ran a surface scan on it to rule out any issues with the device. It passed with zero issues. I cleared the partitions again and re-wrote the image. The pi booted and had the same issue. I tried the 32bit version of the image with the same result. I then tried the raspberry pi OS lite image. Same issues again.

I wrote the Mainsail OS image to an SD Card, and successfully booted off that. I thought that if it was having an issue booting off the SSD for whatever reason, I could allow the SD Card to boot, the manually copy the data across to the SSD and then try booting it again. After successfully booting off the SD Card, I shutdown the system, put the SD Card in to a USB reader, and connected it and the SSD to another linux box. I successfully copied the data to the SSD, adjusted the UUIDs and tried to boot the pi with the SSD. I got a lot further this time, but still had issues.

I tried re-copying the SD Card to the SSD using rpi-clone however it failed very soon in to the operation saying that the device had disappeared. Syslog message indicated tha the XHCI USB device had disconnected.

After some googling, I determined that the current pi kernel has an issue with certain USB devices and the uas (USB Attached SCSI Mass Storage) driver. It seems it hates the JMicron controller that the USB enclosure uses. The fix was to add a line to /boot/cmdline.txt. I just had to get the vendorID and productID of the device, which is available via the dmesg command.

This article was very helpful.

I added usb-storage.quirks=152d:0578:u to the beginning of /boot/cmdline.txt ³, separating it from the subsequent commands with a space. I rebooted the pi with the new setting.

I cleared the partitions on the SSD and used rpi-clone again, and this time it completed successfully.

I shut down the pi, removed the SD Card, and booted with just the SSD connected. SUCCESS! The pi booted quickly this time, with no further errors.

Troubleshooting this issue took much longer than it should have, but that's just the way of it.

I now have a working Mainsail installation. Now to configure it to work with my slightly customised Creality CR6-SE.

Photo by Jainath Ponnala on Unsplash

View all of Pi4b SSD Troubles

If you have a Tello drone - actually this is probably the case for any device that you need to connect to via wifi in order to configure/control from iOS / iPadOS - if you have issues with the app just not detecting the drone even if you're connected to the device's wifi connection, try the following:

1) In the Settings app, scroll down to the particular app settings and check that it has local lan access.

2) Forget your home wifi network so that iOS/iPadOS stops trying to connect to it when it doesn't detect internet access on the drone wifi.

3) Disable Mobile Data. Even if you're connected to the drone wifi and getting an IP address - if Mobile Data is connected, the software will not be able to connect to the drone.

Now it should work. Good luck.

View all of Tello Drone & iOS Wifi Connection Issues

Newer versions of XenServer expect you to use vApps to handle virtual machines auto starting.  This may not be appropriate in some situations.

You can still enable auto-power on via command line on the host [https://support.citrix.com/article/CTX133910], however this just batch starts all VMs at once. You might like a bit more control, particularly if you require the VMs to start up in a particular order.

The method I'm about to explain may not be particularly elegant, but it works for my home lab.

Establish a shell connection to your XenServer / XCP-NG host via SSH or directly on the console. Using PuTTY or some other SSH client that allows you to copy and paste will be really helpful.

You should be in the root user's home directory /root. This should be the default directory you're dropped in to when you first establish your connection

• otherwise just type cd and press enter to go straight there.

Create a new file called vm-autostart.sh with your favourite editor. I like vi as it's usually available.

Paste the following contents and modify the array called vms to suit:

#!/bin/bash

# xe vm-list for name-label, add in start order
vms=("VM1" "VM2" "VM3" "VM4" "VM5" "VM6" "VM7" "VM8" "VM9" "VM10")
wait=42s

# No need to modify below
initwait=2.5m
vmslength=${#vms[@]}
log=/root/vma.log

start_vm () {
   echo -n "[$(date +"%T")] Starting $1 ... " >> ${log}
   /opt/xensource/bin/xe vm-start name-label=$1
   if [ $? -eq 0 ] 
     then 
       echo "Success" >> ${log}
     else 
       echo "FAILED" >> ${log}
   fi

   # Wait if not the last vm
   if [ "$1" != "${vms[${vmslength}-1]}" ]
     then
       echo "Waiting ${wait}" >> ${log}
       sleep ${wait}
   fi
}

echo "[$(date +"%T")] Running autostart script (Waiting ${initwait})" > ${log}
sleep ${initwait}

for vm in ${vms[@]}
do
  start_vm ${vm}
done

echo "[$(date +"%T")] Startup complete." >> ${log}

The vms array takes the list of VM name-label properties. You can see them on the host if you run xe vm-list, or just take a look at your management software for the VM name. If you prefer to use the UUID, just modify the script accordingly.

The wait variable is set at 42 seconds. This is just slightly longer than it takes each of my vms to start up. You may require a bit longer, or you can set it a bit shorter. As my VMs all boot from the hosts local disks, I have the delay set so that there isn't so much contention for disk access. If you're booting from a storage array, then you might not require such a long delay.

The initwait variable is set at 2.5 minutes. This is to allow time for the toolstack to finish starting before trying to start the first VM. If the toolstack hasn't properly started before the first VM attempts to boot, the virtual machine will fail to start and you will have to start it manually. Subsequent machines will usually start, depending on the wait variable.

Save the script and quit the editor when you're happy with it. Remember to set the script to be executable with chmod a+x vm-autostart.sh.

Edit /etc/rc.d/rc.local with your favourite editor.

At the bottom of the file, add a call to your newly create and executable script:

/root/vm-autostart.sh

Save the file and quit the editor.

Make the rc.local script executable:

chmod a+x /etc/rc.d/rc.local

Next time your host restarts, your vms should start automatically. Remember to test the script manually by shutting down all your VMs and then running the script in the shell to see that you didn't inadvertently introduce any errors.

You can track the progress of the script. As soon as your host has rebooted, connect to the shell and either run tail -f /root/vma.log or run less /root/vma.log and press the F key to get the tail (Follow) function.

View all of XenServer / XCP-NG VM AutoStart

In the interest of having this information somewhere handy: Firstly, to successfully install VirtualBox Guest Additions within a server based image:

sudo apt-get install dkms build-essential linux-headers-`uname -r`

I discovered that if you clone an ubuntu server based image, networking stops functioning in the clone. The reason for this is that the new Machine assigns a new MAC address to the NIC. So the Udev rules think it's a new card, and assign it a new device id, like eth1, or eth2, etc.

To prevent this from happening, in your base image, edit /lib/udev/rules.d/75-persistent-net-generator.rules

Search for 'xen', and you'll see a block about ignoring the Xen virtual interfaces. Add the following below it:

 # ignore VirtualBox virtual interfaces
    ATTR{address}=="08:00:27:*", GOTO="persistent_net_generator_end"

Save it, and then remove the file /etc/udev/rules.d/70-persistent-net.rules.

Do the same thing in any cloned images with broken networking, and reboot the VMs.

View all of VirtualBox - Cloning Ubuntu (or Debian) based image issues