Upgrade Ubuntu to version 20.04

Pre-requisite: Services of Motadata and clickhouse should be stopped before starting the upgrade

This is an online upgrade of Ubuntu. Make sure you have an active internet connection. These steps are common for upgrading Motadata master server and Motadata RPE server.

-- command to check ubuntu version:
lsb_release -a

Use the below commands only in Master/Datanode where clickhouse is installed:

apt-mark hold clickhouse-client clickhouse-common-dbg clickhouse-server-base clickhouse-server-common

Install the important updates using below commands:

apt-get update ; apt-get -f install -y ; apt-get upgrade -y ; apt-get dist-upgrade -y ;

Reboot the server:
```
reboot
```

Use the below command if the upgrade 16 to 18:

if [[ $(lsb_release -rs) == 16.04 ]]; then do-release-upgrade; else echo -e "\n*******\nYour current version is not ubuntu 16.04 Pls run this command only in Ubuntu 16.04\n*******\n"; fi

After successful upgrade to 18 it will ask for reboot

Use the below command if the upgrade 18 to 20:

if [[ $(lsb_release -rs) == 18.04 ]]; then do-release-upgrade; else echo -e "\n*******\nYour current version is not ubuntu 18.04 Pls run this command only in Ubuntu 18.04\n*******\n"; fi

After successful upgrade to 20 it will ask for reboot

Download the file -‘ubuntu20-post-upgrade.tar’ from the delieverables of Release 7.6.7 (https://motadata2016.s3.ap-south-1.amazonaws.com/Motadata/7.6.700/Deliverables/Deliverables.zip). Now, move it to the first level of Motadata.
Extract tar ubuntu20-post-upgrade.tar.gz using below command:
```
tar -xvf ubuntu20-post-upgrade.tar.gz
```
Now, run ubuntu20-post-upgrade.sh script using below command:
```
sudo ./ubuntu20-post-upgrade.sh
```
Reboot the Server:
```
reboot
```