Create Linux bridge without losing existing connection

The dillemma: You're accessing your server via SSH through interface eth1.102 with the ip 10.20.0.2/24 and gateway 10.20.0.1. Now you want to add eth1 to a linux bridge so you can hookin VMs on a vlan trunk.

Solution: Create a script which …

Hadoop on demand with Openstack, Cloudinit and Salt

This post will describe the whole process of providing hadoop on demand through Openstack, Cloudinit and Saltstack. We will use Openstack to provision servers on demand, cloudconfig to install salt-master and salt-minion and saltstack to deploy hadoop namenode and datanodes, all fully automated. This makes us able to deploy a …

Neutron Multiple allocation pools single subnet (Solve Fragmented floating ips problem)

In a lab environment in the university I only had access to a list of fragmented public routable IP addresses in a single subnet. For example I got access to the following ips 50.15.15.10, 55.15.15.12-15, 55.15.15.17. But I am not allowed …

Openstack Networking Study Notes

I recommend these links in the following order:

• ScottLowe blog: Using GRE tunnels with OpenvSwitch
• ScottLowe blog: Examining OpenvSwitch traffic patterns
• Hastexto: Neutron Packet Flows (PDF/Presentation)

Docker get private ip address of container

In order to access other containers from a container it's needed to get the private IP address of the other containers. The following command is able to get the private ip address of the container.

$ docker inspect --format="{{.NetworkSettings.IPAddress}}" $CONTAINER_ID_OR_NAME
172.17.0.15

Docker Multiple websites/domains on single ip/host tutorial using a HAproxy as reverse proxy

This post will describe how to expose multiple docker containers running websites on port 80 using HAproxy as a reverse proxy. This makes it possible to run multiple websites on different domains on a single public ip of the host.

The basic setup is to create 1 container for haproxy …

Move first word to end of line (Linux/awk)

Move the first word of a line to the end of line on Linux using AWK. We first store the first column(first word) in the variable t. Then we set the first column to be empty. At last we add a new column after the last column of the …

SSH to server behind a firewall via an SSH tunnel

A server behind a firewall was unaccesible from my home, but another server which is on the same local network had public SSH access from my home. So we can create an SSH tunnel via this public server to the server behind a firewall.

For example the public ssh server …

Recursive karatsuba multiplication in Python

I'm currently taking the class Algorithm: Design and Analysis of Stanford via Coursera and in the class the Karatsuba algorithm got mentioned. I went ahead and implemented it based on the lecture slides.

The Karatsuba algorithm is a fast multiplication algorithm. It's special because it was the first multiplication algorithm …

Using nested tmux over ssh and how to detach a nested tmux

Today I logged in to my laptop at home from work which was already running a tmux session, so thought yea just attach cool can continue with what I was looking at at home. I forgot that the keys would be the same ofcourse, and was unable to use the …