Below is an overview of one proven method to install and configure GVM (formerly OpenVAS) on Ubuntu 20.04. There are two common approaches:

1. Package-Based Installation
   Ubuntu 20.04 provides a “gvm” metapackage. In a simple scenario you can run:

   sudo apt update && sudo apt upgrade -y
   sudo apt install gvm
   sudo gvm-setup
   sudo gvm-check-setup
   

   This method installs the prebuilt components and runs some basic configuration (such as creating an admin user and updating feeds). However, note that sometimes the Ubuntu packages may be incomplete (for example, missing the Greenbone Security Assistant – GSA) so you might need to build or adjust further settings.
   
   

2. Building from Source
   This method (detailed in guides like the HowtoForge tutorial) gives you more control and the latest features. The high-level steps are as follows:

   a. Prepare Your System and Install Dependencies:
   Update your system and install required packages:

   sudo apt update && sudo apt upgrade -y
   sudo apt install software-properties-common build-essential cmake pkg-config libglib2.0-dev libgpgme-dev libgnutls28-dev uuid-dev libssh-gcrypt-dev libldap2-dev doxygen graphviz libradcli-dev libhiredis-dev libpcap-dev bison libksba-dev libsnmp-dev nmap curl wget git texlive-latex-extra texlive-fonts-recommended -y
   

   Also install Yarn (used during build steps):

   curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
   echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
   sudo apt update
   sudo apt install yarn -y
   

   And install PostgreSQL (which is used by GVM):

   sudo apt install postgresql postgresql-contrib postgresql-server-dev-all -y
   

   Then configure the PostgreSQL database:

   sudo -u postgres createuser -DRS gvm
   sudo -u postgres createdb -O gvm gvmd
   sudo -u postgres psql gvmd -c "create role dba with superuser noinherit;"
   sudo -u postgres psql gvmd -c "grant dba to gvm;"
   sudo -u postgres psql gvmd -c "create extension "uuid-ossp";"
   sudo -u postgres psql gvmd -c "create extension "pgcrypto";"

   b. Create a Dedicated GVM User and Set Up Environment:

   sudo adduser --disabled-password --home /opt/gvm --gecos "GVM User" gvm
   sudo mkdir /opt/gvm
   sudo chown gvm:gvm /opt/gvm
   echo 'export PATH="$PATH:/opt/gvm/bin:/opt/gvm/sbin:/opt/gvm/.local/bin"' | sudo tee /etc/profile.d/gvm.sh
   sudo chmod 0755 /etc/profile.d/gvm.sh
   source /etc/profile.d/gvm.sh
   echo "/opt/gvm/lib" | sudo tee /etc/ld.so.conf.d/gvm.conf
   sudo ldconfig
   

   c. Download the Source Code:
   Switch to the gvm user and clone the repositories:

   sudo -u gvm -H mkdir -p /opt/gvm/src && cd /opt/gvm/src
   sudo -u gvm -H git clone -b gvm-libs-20.08 --single-branch https://github.com/greenbone/gvm-libs.git
   sudo -u gvm -H git clone -b openvas-20.08 --single-branch https://github.com/greenbone/openvas.git
   sudo -u gvm -H git clone -b gvmd-20.08 --single-branch https://github.com/greenbone/gvmd.git
   sudo -u gvm -H git clone -b gsa-20.08 --single-branch https://github.com/greenbone/gsa.git
   sudo -u gvm -H git clone -b ospd-openvas-20.08 --single-branch https://github.com/greenbone/ospd-openvas.git

   d. Build and Install the Components:
   For each component, create a build directory, run CMake, and install. For example, for gvm-libs:

   cd gvm-libs
   mkdir build && cd build
   cmake -DCMAKE_INSTALL_PREFIX=/opt/gvm ..
   make
   sudo make install
   

   Repeat similar steps for OpenVAS, gvmd, and finally GSA. Don’t forget to install ospd-openvas and adjust the scanner settings:

   sudo gvmd --create-user=admin --password=admin
   gvmd --get-scanners  # then modify the default scanner if needed:
   sudo gvmd --modify-scanner= --scanner-host=/var/run/ospd/ospd.sock

   e. Update Vulnerability Feeds and Generate Certificates:
   Update the NVTs, CERT, and SCAP feeds:

   sudo -u gvm greenbone-nvt-sync
   sudo -u gvm greenbone-feed-sync --type CERT
   sudo -u gvm greenbone-feed-sync --type SCAP
   

   Generate certificates:

   sudo gvm-manage-certs -a

   f. Configure and Start Services:
   Create and enable systemd service files for gvmd, gsad (the web interface), and ospd-openvas. Once services are set up and started (or use the provided script), you can verify that gvmd, gsad, and the scanner are running.

   Finally, access the GVM web interface (typically via HTTPS on port 443 or 9392) and log in using the admin credentials you set.

   Detailed instructions and sample systemd files are provided in guides like the HowtoForge tutorial.
   
   

In Summary:

• The package-based approach (using apt install gvm) is the quickest but might require tweaks if components like GSA are missing.
• The source build approach gives you the latest GVM 20.x components (or higher, if available) with full control over configuration.

Choose the method that best suits your experience and requirements. For more in-depth instructions and troubleshooting tips, refer to tutorials like the one on HowtoForge and discussions on the Greenbone Community Forum.