Whether you need to build a Kubernets cluster, an openstack instance, a hadoop cluster…etc, Canonical has developed a tool called conjure-up. This tool can build these whole environments for the purpose of development and testing, or small environments in a few minutes.
To install it on Ubuntu Xenial:
sudo snap install conjure-up --classic
To start the interactive deployment CLI, just run
or specify the exact software that you need to deploy (called spells in its terminology):
That’s it, Enjoy!
You add a user to group docker so that you can run docker commands without having to be root or a sudoer.
On an Ubuntu 16.04 server which authenticates against AD using PBIS, I added users to group docker, but wasn’t getting recognized at all and had to use sudo, which defeats the purpose.
All I did was the following:
- Edit /etc/group
- go to the bottom of the file where you will find the docker group
- change the name of the AD group from lower case to upper case characters and save, e.g.:
docker:x:999:hobba\socrat to docker:x:999:HOBBA\socrat
Ansible is an amazing piece of configuration management software. Among its amazing features is that it’s totally agentless and the only 2 packages that it needs on any host are python and an SSH server.
Today we will create a playbook that will do the following:
- Add the stable docker repository to the software sources
- Add the gpg key
- install docker-ce package
It’s assumed that you have already added all required hosts to /etc/ansible/hosts and I’m naming this group “swarm”
- hosts: swarm
- name: add docker repo
repo="deb https://download.docker.com/linux/ubuntu xenial stable"
- name: install repo gpg key
- name: refresh cache and install docker-ce
Sources: Ansible Documentation
For old commands, just edit .bash_history and delete whatever you want from inside.
For commands in the current session, just run this command before you exit:
The $HISTFILE environment variable is the one which holds your commands and will flush to the file once you exit the session.
And it’s FREE! I wouldn’t have written a blog entry for something except if it was such an amazing one:
In brief, sometimes a conflict occurs between some firewalls and the TCP SACK. In my case, the upload was severely affected and reached upload speeds of a few kilobytes over a LAN!
The following command disables TCP SACK and fixes the slow upload on all Ethernet cards:
sudo sysctl -w net.ipv4.tcp_sack=0
To make it permanent, edit /etc/sysctl.conf and add this line
After it is moved to another host, since it is a sparse file, the qcow2 takes the full space, e.g. if it was dynamically set to 100GB, it will take 100GB, even if only 50 GB were actually used.
I could get back more than 20 GB from my Win7 VM (from a 50 GB file) using this:
sudo qemu-img convert -O qcow2 win7.qcow2 win7_small.qcow2