linux – Page 6 – Kev's Development Toolbox

May 16, 2019May 16, 2019

Pause when sudo’ing commands on Ubuntu 18.04

I just installed an Ubuntu 18.04 server and noticed when using sudo for commands, it would pause for about 10 secs then execute the command.

A quick google found this post, mentioning that if you change the hostname during install, you should manually add the same hostname to the /etc/hosts for 127.0.0.1.

I did this and now sudo commands execute instantly as expected.

May 15, 2019May 15, 2019

Installing a desktop on Ubuntu 18.04 server

Ubuntu 18.04 Server does not come with a desktop by default, but any of the normally available desktops can be installed with the tasksel util.

sudo apt-get install tasksel

List available desktop installations (and other installs/collection of packages):

tasksel --list-tasks

Select required desktop from displayed list and install, e.g.:

sudo tasksel install lubuntu-desktop

Wait for install to complete, reboot, done.

December 2, 2018December 3, 2018

Rancher RKE Kubernetes install notes

Rancher’s RKE is a Kubernetes cluster installer – see more here.

Pre-reqs:

Docker must be running on the client machine where you are going to run the rke setup tool
The docs are not obvious, but the rke tool is run on a client machine to provision your cluster, it is not run on any of the target cluster nodes

Notes using Ubuntu 16.04 server.

Remove prior Docker installs:

sudo apt-get remove docker docker-engine docker.io

Create docker group and add user to docker group:

sudo groupadd docker
usermod -aG docker <user_name>

Install per Docker CE install steps here, or use the Rancher provider install script here.

Supported Docker versions for RKE (as of Dec 2018) are: 1.11.x 1.12.x 1.13.x 17.03.x

Configure Docker daemon to listen for incoming requests on 2376, as per steps here.

Using ‘rke config’ with the default/minimal cluster.yml here, and then install/setup with ‘rke up’

If you didn’t change the name of the cluster.yml file, after the install is complete, you’ll have a kube_config_cluster.yml file in the same dir which you can use with kubectl to interact with you cluster, or add it into your existing ~/.kube/config file

November 30, 2018November 30, 2018

Updating Kubernetes master node and worker node config if an ip address changes

I have a test Kubernetes cluster running with a CentOS7 master nodes, and 4 CentOS7 worker nodes, under VMware ESXi. The ip addresses of each of the VMs is from DHCP, and as I hadn’t booted these VMs for a while, when I recently started them up they all got new IP addresses, so the cluster would not start up, and all the .kube/config files were now referring to incorrect IP addresses. Note to self – this is a good reason why you should use DNS names for the nodes in your cluster instead of ip addresses, especially IP addresses that can change.

Anyway, to restore my cluster back to a working state, I reinitialized the master node, and the joined the workers to the new master.

First on the master:

sudo kubeadm reset
sudo kubeadm init --pod-network-cidr=10.244.0.0/16

#take a copy of the kubeadm join command to run on the workers

#copy kube config for local kubectl
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

#apply networking overlay
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.8.0/Documentation/kube-flannel.yml
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.8.0/Documentation/kube-flannel-rbac.yml

#for each of the worker nodes, scp the config file to each node for local kubectl use
scp /etc/kubernetes/admin.conf kev@192.168.1.86:~/.kube/config

On each of the worker nodes:

sudo kubeadm reset

#then run the kubeadm join command shown from the master when you ran kubeadm init