sudo kubeadmin init returns with: [ERROR Swap]: running with swap on is not supported. Please disable swap

Posted on 26 May 2020 by kosmas

Problem

You are trying to set up kubernetes on your local machine but trying to use initialize it with kubeadmin init, returns the following error:

[init] Using Kubernetes version: v1.18.3
[preflight] Running pre-flight checks
error execution phase preflight: [preflight] Some fatal errors occurred:
        [ERROR Swap]: running with swap on is not supported. Please disable swap
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
To see the stack trace of this error execute with --v=5 or higher

				
					
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						[init] Using Kubernetes version: v1.18.3
[preflight] Running pre-flight checks
error execution phase preflight: [preflight] Some fatal errors occurred:
        [ERROR Swap]: running with swap on is not supported. Please disable swap
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
To see the stack trace of this error execute with --v=5 or higher

					

			

Solution

Switch the swap to off (Ubuntu command below) and try again.

sudo swapoff -a

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						sudo swapoff -a

Setting up worldPing with Grafana running in docker

Posted on 15 May 2020 by kosmas

You would like to test worldPing (https://worldping.raintank.io/worldping/) in your local environment for evaluation purposes.

Install Grafana with docker as described here (https://grafana.com/docs/grafana/latest/installation/docker/) and give it a name (ie grafana)
Login to the grafana container and install the worldPing plugin:

$ docker exec -it grafana /bin/bash
bash-5.0$ grafana-cli plugins install raintank-worldping-app

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						$ docker exec -it grafana /bin/bash
bash-5.0$ grafana-cli plugins install raintank-worldping-app

Exit from the container and stop and start it

bash-5.0$ exit
$ docker stop grafana
$ docker start grafana

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						bash-5.0$ exit
$ docker stop grafana
$ docker start grafana

Login to your grafana installation on the browser (localhost:3000) and go to the section for the plugins to find worldPing
To be able to enable it you will need an API key from Grafana Cloud, so create a free account (https://grafana.com/signup/starter/connect-account)
Create an API key (Security – API Keys – Add API Key)
Go back to Grafana web UI and add the API key so you can enable the worldPing. Add an endpoint to check and select the services to check (DNS, Ping, HTTP, HTTPS)
Leave it running for a few minutes and check the dashboards afterwards.
Remember to Disable if you want to go back to it again in the near future, or Destroy the endpoint if you do not need it anymore.

ssh-add, Gitlab CI/CD with alpine image

Posted on 27 April 2020 by kosmas

Problem

Trying to use the usual way of adding Gitlab’s key to the ssh agent, is not working in alpine image (but it works in debian/ubuntu), and you get the following error message:

 - ssh-add <(echo "$GITLABCICD_PRIVATE_KEY")
/bin/sh: syntax error: unexpected "("

Solution

Try to use the following instead:

  - echo "$GITLABCICD_PRIVATE_KEY" | ssh-add -

AWS allowing access to Billing to IAM user

Posted on 17 April 2020 by kosmas

Problem

When you create a new AWS account the access to Billing for IAM users is not enabled by default.

Solution

In order to allow access you have to follow the steps below:

Login to your AWS account with your root user (email and password)
Go to the top right drop down ‘My Account’
Find the section that is called ‘IAM User and Role Access to Billing information’, use ‘Edit’, tick the box ‘Enable access’ and then ‘Update’.

More information can be found in the Amazon’s help page https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/control-access-billing.html#ControllingAccessWebsite-Activate

Get a list of your Route53 subdomains using aws cli docker image

Posted on 13 March 2020 by kosmas

Problem

You would like to have a list of your subdomains for a specific domain (hosted zone), that are hosted in Amazon’s Route 53.

Solution

You can install the aws cli docker image from here https://github.com/cgswong/docker-aws if you don’t want to install the aws cli in your computer.

You can afterwards start the container with:

docker run -it cgswong/aws:latest

Then configure it by running the following and adding your credentials and zone:

efe9881d4fd:/tmp# aws configure
 AWS Access Key ID [None]: aws_access_key_id
 AWS Secret Access Key [None]: aws_secret_access_key
 Default region name [None]: eu-central-1
 Default output format [None]:

Then run the first command to get a list of the hosted zones and get the id of the hosted zone you want to find the subdomains for:

3efe9881d4fd:/tmp# aws route53 list-hosted-zones
{
    "HostedZones": [
        {
            "ResourceRecordSetCount": 2, 
            "CallerReference": "RISWorkflow-RD:xxxxx", 
            "Config": {
                "Comment": "HostedZone created by Route53 Registrar", 
                "PrivateZone": false
            }, 
            "Id": "/hostedzone/HOSTEDZONEID", 
            "Name": "domain.net."
        },

Then pick the HOSTEDZONEID and run the following to get a list of subdomains for that domain:

3efe9881d4fd:/tmp# aws route53 list-resource-record-sets --hosted-zone="HOSTEDZONEID" | grep "Name" | uniq

   "Name": "alpah.domain.com.",                                                                                                                                                                                                                                             
   "Name": "beta.domain.com.",                                                                                                                                                                                                                                       
   "Name": "lamda.domain.com.",
......

Find devices with their IPs in your local network

Posted on 10 March 2020 by kosmas

Problem

You would like to have a list of IPs or MAC address for the device in your network

Solution

Use the ARP protocol’s command:

$ arp -a

dv1.home (192.168.1.102) at 48:xx:xx:xx:xx:xx [ether] on wlp4s0
dv2.home (192.168.1.127) at a4:xx:xx:xx:xx:xx [ether] on wlp4s0
...

Terraform Cloud – error when trying to initialize

Posted on 24 February 2020 by kosmas

Problem

You would like to start using Terraform Cloud and when trying to initialize it with the new remote backend (app.terraform.io), you get the following error:

Error: Required token could not be found

Make sure you configured a credentials block for app.terraform.io in your CLI
Config File.

Solution

Follow the instructions here https://www.terraform.io/docs/cloud/free/index.html and create a file ~/.terraformrc (in linux) with an API token.

Checking and enabling slow query log in MySQL

Posted on 5 February 2020 by kosmas

Problem

You would like to check and enable the slow query log for MySQL.

Solution

To check if the log is on run the following query

show global variables like '%slow_queries'

To switch it on if the above shows it as OFF, use the following:

set @@GLOBAL.log_slow_queries = 'ON'

Find your public IP address from linux command line

Posted on 13 January 2020 by kosmas

Problem

You would like to find out your public IP from the command line without using an online service

Solution

Use dig like the following line (taken from https://www.cyberciti.biz/faq/how-to-find-my-public-ip-address-from-command-line-on-a-linux/):

dig +short myip.opendns.com @resolver1.opendns.com

you could also add it as an alias:

alias myip=”dig +short myip.opendns.com @resolver1.opendns.com”

Get a list for all crontab jobs in a server

Posted on 6 December 2019 by kosmas

To get a list of all the installed crontab jobs on a server use the following (taken from https://stackoverflow.com/a/134944)

for user in $(cut -f1 -d: /etc/passwd); do echo $user; crontab -u $user -l; done

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sudo kubeadmin init returns with: [ERROR Swap]: running with swap on is not supported. Please disable swap

Problem

Solution

Setting up worldPing with Grafana running in docker

ssh-add, Gitlab CI/CD with alpine image

Problem

Solution

AWS allowing access to Billing to IAM user

Problem

Solution

Get a list of your Route53 subdomains using aws cli docker image

Problem

Solution

Find devices with their IPs in your local network

Problem

Solution

Terraform Cloud – error when trying to initialize

Problem

Solution

Checking and enabling slow query log in MySQL

Solution

Find your public IP address from linux command line

Problem

Solution

Get a list for all crontab jobs in a server