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Linux Ubuntu Images

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This page describes the Ubuntu images supported on Semaphore Cloud.

Overview​

The Operating System image defines what OS and software are pre-installed in your agents.

This page describes OS images to run on Linux-based Semaphore Cloud machines. You can add more OS options using self-hosted agents.

Installing packages​

You have full sudo passwordless permissions to install and modify OS packages as needed. Ubuntu package manager is apt.

To install a package, run:

sudo apt-get update
sudo apt-get install -y <package-name>
info

Packages are installed from a package repository located near the machines for more performance.

Disabled repositories​

Due to occasional issues with some of the repositories that break the pipeline during the apt-get update command, the following package sources repositories have been disabled and moved to /etc/apt/sources.list.d/disabled:

  • azure-cli.list
  • devel_kubic_libcontainers_stable.list
  • docker.list
  • firefox.list
  • git.list
  • google-cloud-sdk.list
  • gradle.list
  • helm.list
  • pypy.list
  • python.list
  • yarn.list

If you need any of these package repositories, execute the following command:

sudo mv /etc/apt/sources.list.d/disabled/<package-repository-file.list> /etc/apt/sources.list.d/
sudo apt-get update

Nested virtualization​

Linux-based machines support nested virtualization. You can create virtual machines inside the virtual machine running your agent using [libvirt]

Follow these commands to use nested virtualization:

  1. Check that nested virtualization is supported. The output should be 0 
    grep -cw vmx /proc/cpuinfo
  2. Install the required packages 
    sudo apt-get install -y uvtool sshpass net-tools netcat-openbsd
  3. Download prebuilt Ubuntu cloud image 
    uvt-simplestreams-libvirt --verbose sync --source http://cloud-images.ubuntu.com/daily release=focal arch=amd64
    uvt-simplestreams-libvirt query
  4. Create a new SSH keypair 
    rm -rf ~/.ssh/id_rsa
    echo | ssh-keygen -t rsa  -f ~/.ssh/id_rsa
  5. Create the VM 
    uvt-kvm create vm1 --memory 1024 --cpu 1 --disk 4 --password ubuntu --bridge virbr0
    uvt-kvm list
  6. Wait for the machine to be up and IP to be available 
    IP=""
    while [ -z $IP ];do IP=$(arp -an | grep $(virsh dumpxml vm1| grep "mac address" | cut -d"'" -f2)|cut -d"(" -f2|cut -d")" -f1);done
    echo $IP
    while ! nc -w5 -z $IP 22; do  echo "Sleep while $IP is up";sleep 1; done
  7. Run the commands in the VM using SSH. For example, this runs uname -a 
    sshpass -p "ubuntu" -v  ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no ubuntu@$IP -t 'uname -a'

The predefined default network for nested virtualization is 192.168.123.0/24. The base VM provides virbr0 interface with the IP address: 192.168.123.1.

See also​