The VMWare Clarity Design System documentation is a bit vague about how modal dialogs should be handled. The examples presented are not really appropriate for real-world applications, where dialogs need to be reusable components, usually containing forms. So, here’s a more realistic example of how to use modal dialogs in clarity applications. The code is available as a stackblitz at What we want to achieve is a modal component which can be called from anywhere in the application and which takes a model object as input and returns a modified model as output (i.e. the dialog does nothing with the object except allow the user to edit it – the caller has control over what to do with the[…]

I was looking for a simple  way to use Let’s Encrypt to enable https for a web site and I found a Docker image nmarus/docker-haproxy-certbot which met my needs. Remember, Let’s Encrypt represents a complete break from traditional certificate issuers in that: (a) its free. (b) certificate creation, installation and renewal is fully automated. These are huge advantages relative to working with the previous certificate issuers and anyone who deploys anything to the internet should immediately take advantage of them. Let’s Encrypt’s audacious goal is to improve the whole internet by getting everyone to use https. Let’s Encrypt provides a “certbot” which handles the whole lifecycle of the certificates for you. There’s plenty of Let’s Encrypt documentation on how to install the[…]

We’ve been using the free ESXi ghettoVCB backup utility for the last 5 years to backup about 150 VMs daily without a glitch. ghettoVCB snapshots the VM, copies away the files (with a configurable retention period) and then removes the snapshot. The resulting backup is a snapshot of the VM which means that when you need it, you can directly run the backup copy of the VM with ESXi and start it without having to restore it. ghettoVCB is fast and reliable (it copies sparse disks correctly to an NFS backup share so the resulting backup is as compact as the original VM disks). ghettoVCB has no deduplication capabilities, so its usually not appropriate for offsite backup of VMs. We[…]

Borg backup ( is an open source backup tool which, in addition to the usual backup features like strong client-side encryption and compression, has several important characteristics which make it particularly suitable for handling large offsite backups (like virtual machine backups): Deduplication: this ensures that even if the source files move or change names, that they will not be re-backed up unnecessarily. The backup can be moved. Borg backups are just directories – this means that you can make the first, full backup locally, copy it to the destination via a USB disk and the continue incremental backups over the network. We are currently using borg for several offsite backups, including a weekly offsite backup of VMWare ghettovcb local backups[…]

We’ve been recently running rest APIs on active-active server pairs (docker containers running on pairs of VMs on separate hosts) with postgres-BDR (multi-master bidirectional replication) for fault-tolerant storage and a pair of fault-tolerant HAProxy instances for incoming request routing. This is a robust setup which provides zero downtime during rolling updates or hardware maintenance or failure. However, clustering scheduled jobs (i.e. ensuring that scheduled jobs execute exactly once) becomes a problem in this configuration. Multi-master replicated databases avoid a single point of failure but they are not suitable for use with database-based clustered schedulers like Quartz, so we needed to consider other options. There are complex clustered job schedulers, but we wanted to keep it simple and use Linux crond for scheduling. We finally settled on using keepalived to maintain a single master across the cluster[…]

We live in an old house, on three levels. Its always been a challenge to achieve consistent wifi coverage throughout the house. We neglected to install ethernet cabling when we renovated and have been struggling with wifi issues ever since. We tried power-line networking (Devolo, TP-Link) and, although it worked most of the time, it provided very inconsistent performance and it was impossible to figure out why. We then reverted to a central wireless router and range extenders (Apple, TP-Link). Coverage was pretty bad in many parts of the house. Last weekend, we installed the AmplifiHD mesh networking system from Ubiquiti and we finally have the full performance of our internet provider (40-60Mbps LTE, depending on the time of day) from any or[…]

I’ve been using an i5 Intel NUC at home as a home server. I initially installed ESX on the NUC and ran an ubuntu VM with iptables, DNS, DHCP etc. However, I wanted to put the firewall between the home network and the LTE router, so I needed two network interfaces. The NUC only has one, so I thought I’d use VLANs to split the network.  That turned out to be pretty complicated to manage so I ended up buying a USB3 ethernet adapter (AX88179) for the NUC instead. Getting that to work with ESX was a pain (I tried pass-through, but couldn’t get it to work reliably), so in the end I replaced ESX on the NUC with KVM. Worked great –[…]

We’ve been using Devolo powerline networking at home for years – we have an old house with wifi-proof walls. We’d been having plenty of problems with them, possibly due to overheating of the wifi plugs. After replacing the dLan 500 adapters with the more expensive Devolo dLan Pro adapters without any improvement, I finally decided to try TP-LINK AV500s instead. The TP-LINKs are much cheaper (base plug plus two WLAN repeaters for < EUR 100). They are also compatible with the Devolo dLan 500s, so I’m still using a few of the Devolos (for a printer and in the cellar). Unfortunately they don’t perform better than the Devolos – I still get about 30Mbit throughput (measured with iperf between two devices connected by ethernet to the[…]