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Wednesday, 21 December, 2016

Wifi christmas tree coding

Since the last posting I connected the christmas tree to an esp8266. I used a Wemos D1 mini for this, which is a very nice and complete board to develop with.

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Monday, 19 December, 2016

Wifi christmastree

While browsing through the Kwantum folder, I found an intresting, small and cheap christmastree.

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Thursday, 24 March, 2016

Proxmox 4.1 lxcfs

Since Proxmox 4.1 I've had a number of issue's on my servers.

The first (and smallest) issue has to do with my Thinlinc installations. The agent component can hang after running a specific cronjob. A "ps" process starts to hang. The only way to resolv this is to restart the zone. This behaviour seems to be related to the lxcfs package on version 0.13-pve3. Later versions seem to resolve this.

The second issue was much more of a problem. This manifests itself as a server with very high load (>12), lots of processes (normally 1400, now > 10.000) but otherwise responding fine. Everything that is running in the lxc containers seems to hang on IO. While checking the processlist further (before rebooting the server, as this seems the only way out), the output of pstree shows something intresting.

| |-systemd-journal
| `-systemd-logind
|-lxcfs-+-lxcfs---lxcfs
| `-671*[{lxcfs}]
|-ntpd
|-pmxcfs-+-{cfs_loop}
| |-8*[{pmxcfs}]

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Wednesday, 30 December, 2015

Proxmox 4 migration issues

With the introduction of Proxmox 4 a rather large change was introduced. The combination of KVM and OpenVZ was changed to KVM and LXC. The big upside of this is a recent kernel, changing up from 2.6.36 (released 2010) to 4.2 (currently).

But with the change from OpenVZ to LXC come some changes which make a migration less trivial (depending of the amount of features that are in use with OpenVZ).

The Proxmox Wiki has some good information on migrating from Proxmox 3 to Proxmox 4. I have a couple of issue's I ran into during a couple of migrations that I will share here. Maybe it is of use to someone else. Keep in mind I only run Debian containers, so other distributions might have other issue's.

Inotify

When running a larger amount of containers, it is quite possible you're going to run out of inotify instances. Default this is set to 128 (at least it was on my system). After the first migration I started to get into issues after restoring a couple of containers. The errors pointed to this setting. After increasing the value the problems went away:

sysctl -w fs.inotify.max_user_instances=8192

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Monday, 19 October, 2015

Thinlinc reverse proxy

I ran into this program a while ago when I wanted to run the HTML5 ThinLinc client behind a reverse proxy. The HTML5 client has a number of references in it (and a redirect) that refers to the root of the webserver. So serving the client from a url like

https://portal.external.com/thinlinc

just doesn't work.

But we have nginx and with some pointers from the excellent people at Cendio I got it working :)

To make the setup a little bit more clear, I wanted to do this:

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Saturday, 18 July, 2015

Veeam Jaguar fix

The other day there arrived a package for me at work from Veeam. Having ordered nothing and having to do nothing to do with VMWare I was confused.

Unpacking the parcel showed a Jaguar remote controlled car with the Veeam logo on its roof.

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Sunday, 12 July, 2015

Beveiliging banken websites

Toen ik vanmorgen een transactie uitvoerde via mijn bank (ASNBank) zag ik dat deze netjes een score van 10 aangaf in ssleuth. Deze add-on is overigens erg handig om een idee te krijgen of de verbinding tussen je webbrowser en de webserver van het website een beetje veilig is. Uiteraard zegt dit niets over de veiligheid van de applicatie bij de bank.

Ik vroeg me daarna af hoe de websites van de verschilende banken zich verhouden, zetten ze allemaal een veilige verbinding op met de webbrowser?

Ik heb de volgende banken even snel gescanned:

  • ABN/AMRO Bank
  • ASN Bank
  • ING Bank
  • KNAB
  • Rabobank
  • SNS Bank
De test is vrij simpel, SSLabs heeft een handige tool die makkelijk en snel inzicht geeft in de beveilinging van de verbinding tussen de webbrowser en de webserver. SSLlabs geeft ook een waardering aan een website, varierend van een F (slecht) tot A+ (uitmuntend). Alhoewel dat een indruk geeft is het zeker niet het hele verhaal.

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Tuesday, 14 April, 2015

MendelMax 2.5 Z axis support

One of the problems I have with the MendelMax 2.5 is the Z axis. The binding of the axis was and issue and the threads that were delivered with the kit had a huge wobble.

I already started to modify the axis by using the "floating" setup, where the lead screws are detached from the X axis. I used this setup:

Ohmeye z axis isolation

This wasn't enough and I ended up reengineering the whole Z axis setup. The last part was a support for the lead screws, so they were no longer hanging from the stepper motors. The idea is that we put bearings below the lead screws so they are supported, can rotate freely and have no side to side movement.

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