Multiple Mosquitto instances on Debian with Systemd

I have been playing for quite a while MQTT to have my Arduino devices communicate with Node-Red for all kinds of automation. Due to the constraints of the Arduino’s, so far I have not been able to effectively secure this as SSL/TLS is not an option on these devices.

Mosquitto supports multiple listeners out of the box though aside from the listener-specific settings all listeners share the same global (e.g. authentication and plugin) settings. To secure my setup and to work on a more permanent solution I needed different settings per listener for which multiple Mosquitto instances are required (i.e. multiple instances of the mosquitto daemon with their configuration and listeners different IP addresses / ports). This was not difficult on my Debian server but as I did not find much documentation on this I will document the necessary steps in this post.

Continue reading “Multiple Mosquitto instances on Debian with Systemd”

MacOS Server Replacement #2 – Migrating PostgreSQL

As part of the migration of my MacOS Server to Linux the next service to migrate is my PostgreSQL engine. Although PostgreSQL had already been hidden in MacOS Server for some time, it still was included (as internal services like ProfileManager and Calendar and Addressbook Server depend on it.  Despite it being hidden, I had still enabled it (manually) and hosted my PostgreSQL databases on my MacOS Server for ages. Despite migrations sometimes being a pain (i.e. not automatic) this worked well so far, including integrating it with the MacOS Server way of using transaction logs for offline backups. (so I will also have to look for a new way to do this). Continue reading “MacOS Server Replacement #2 – Migrating PostgreSQL”

MacOS Server Replacement #1 – Migrating MySQL to MariaDB

As part of the migration of my MacOS Server to Linux the first service to migrate is my MySQL 5.7 engine. Although MySQL is not part of MacOS Server anymore for a long time (and I had installed it separately), I will cover the migration here as 1) I still had it running on my MacOS Server and 2) the migration wasn’t smooth so decided to share my learnings here. Continue reading “MacOS Server Replacement #1 – Migrating MySQL to MariaDB”

Downgrading grub2 to grub legacy on Debian

Today I attempted to migrate my legacy Linux server to a VM on my ESXi server using VMWare vCenter Converter Standalone. Unfortunately the process failed after about 4 hours of processing with the error message “__FAILED: An error occurred during the conversion.__”… well, that was very helpful!
Fortunately the VMWare Converter allows to save the logs, in which after a bit of digging I found the following error:
[2011-01-01 22:17:14.338 10552 error ‘App’] [task,344] [LRO] Unexpected Exception: converter.fault.CloneFault
[2011-01-01 22:17:14.401 10552 info ‘App’] [task,373] [task-5] — ERROR — Convert: converter.fault.CloneFault
(converter.fault.CloneFault) {
dynamicType = ,
faultCause = (vmodl.MethodFault) null,
description = “GrubInstaller::InstallGrub: /usr/lib/vmware-converter/ failed with return code: 127, and message:
/ line 37: grub: command not found
Error running GRUB
Error running through chroot into /mnt/p2v-src-root
msg = “”,
Apparently it attempted to make the converted VM bootable by executing grub again. This failed because my Debian system (running testing for a long time) had migrated to grub2 ages ago. Since googling didn’t render any hints and it would be a temporary move anyway as I am migrating everything off to other servers, I decided to downgrade grub to the legacy grub version available. Below is a description of the steps to achieve this.

1 Downgrade from grub2 to grub legacy
Before you start make a backup of the current grub2 configuration with:
sudo tar -cvzf /boot/grub2-backout.tar.gz /etc/grub.d /boot/grub
~~Please note that I am using sudo to execute commands as root. If you don’t use sudo, simply login as root and remove the sudo from each command.~~

To get starte with the downgrade, get the list of grub packages installed as you need to remove them all (sounds more dangerous than it is). Get the list and store and show it with the following command:
dpkg -l grub\* | egrep “^ii ” | tee /boot/grub2-backout.list
which on my system gave:
ii grub 0.97-63 GRand Unified Bootloader (dummy package)
ii grub-common 1.98+20100804- GRand Unified Bootloader, version 2 (common
ii grub-doc 0.97-63 Documentation for GRand Unified Bootloader (
ii grub-legacy-do 0.97-63 Documentation for GRUB Legacy
ii grub-pc 1.98+20100804- GRand Unified Bootloader, version 2 (PC/BIOS
With the above 2 pieces of output in /boot/ you should be able to recover and rollback the procedure below in case anything goes wrong. See under Rollback below for the steps to revert this procedure.

First purge the current grub installation (please note this __is__ dangerous as it makes your system unbootable) and install the “~~legacy~~” grub package. Please be aware that the following statements will not just remove the packages, but also your all configuration (that’s why you needed the backup).
sudo apt-get remove –purge `dpkg -l grub\* | egrep “^ii ” | cut -d\ -f 3`
sudo apt-get install grub-legacy
The first line above automatically deinstalls all grub packages and their configuration automatically. You can also specify yourself which packages to remove by writing your ~~apt-get remove~~ statement yourself, just make sure you get rid of everything!

Next let grub install itself on your MBR of your primary harddisk ~~/dev/sda~~ in my case with:
sudo grub-install /dev/sda
which should give output like:
Searching for GRUB installation directory … found: /boot/grub
Installation finished. No error reported.
This is the contents of the device map /boot/grub/
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install’.

(hd0) /dev/sda
(hd1) /dev/sdb

If the output is similar (the list of devices is obviously depending on your system’s configuration), you have succesfully installed grub on your harddisk, now it is time to let grub regenerate its configuration with the following command:
sudo update-grub
Which should produc output similar to
Searching for GRUB installation directory … found: /boot/grub
Searching for default file … found: /boot/grub/default
Testing for an existing GRUB menu.lst file …

Generating /boot/grub/menu.lst
Searching for splash image … none found, skipping …
Found kernel: /boot/vmlinuz-2.6.32-trunk-686-bigmem
Found kernel: /boot/vmlinuz-2.6.32-5-686-bigmem
Updating /boot/grub/menu.lst … done
If your output again looks similar (obviously the list of kernels may differ), congratulations! You have successfully downgraded to grub.

Please note that the grub boot menu created has been automatically generated, so any customizations you made to the boot menu are lost. In case you originally had made customizations made in your menu.lst before you upgraded to grub2, you may be able to see those by executing
diff -wu /boot/grub/menu.lst /boot/grub/menu.lst_backup_by_grub2_postinst | more
Putting them back in ~~/boot/grub/menu.lst~~ is unfortunately a manual step, but doable if you have something to start with.

Now it’s time to test the downgrade by rebooting… fingers crossed!

Now I still need to retry to virtualize my legacy Linux server, but that’s something for tomorrow…

1 Rollback
In case anything goes bad during your downgrade, you should be able to roll things back with the following three commands:
sudo apt-get remove –purge `dpkg -l grub\* | egrep “^ii ” | cut -d\ -f 3`
sudo apt-get install `cut -d\ -f 3 < /boot/grub2-backout.list`
sudo tar -xzf /boot/grub2-backout.tar.gz

Configuring IP aliases cleanly on Debian

I like using different IP addresses for different services on my internal network. Thanks to RFC1918 this is no problem at all, as there are several network ranges dedicated for private networks. Using a firewall with that supports NAT (something people didn’t think of yet when writing the RFC) gives a maximum amount of flexibility when moving services around between servers and keeping things simple.

Setting up network interfaces with multiple interfaces is not really supported by Debian’s ifupdown tools. Yes you can do this easily by adding the necessary calls to the ip utility to your network interface definitions, but this is ugly and error-prone. That’s why I came up with the attached script, which adds support for the keyword aliases to your /etc/network/interfaces configuration so you can define additional IP addresses like this:

iface eth0 inet static

Bringing up or down the interface will automatically add or remove the aliases. Please note that aliases added this way should always be on the same network as the primary address of the interface. To have multiple addresses on the same physical interfaces you need to use vlan’s or alias devices.

To install the script on you Debian host, simply save the script attached to this post as a file called aliases in your current directory and execute the following commands as root:

chmod 755 aliases
chown root.root aliases
cp aliases /etc/network/if-up.d
ln -s ../if-up.d/aliases /etc/network/if-down.d

And add your aliases to your devices in /etc/network/interfaces