How to Install postgresql-client-11 on Ubuntu 18.04
Install it from PostgreSQL's own apt repository, adapted from these instructions.

sudo apt-get install curl ca-certificates gnupg
curl https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main" &gt; /etc/apt/sources.list.d/pgdg.list'
sudo apt-get update
sudo apt install postgresql-client-11
pg_basebackup -V



  pg_basebackup (PostgreSQL) 11.7 (Ubuntu 11.7-1.pgdg18.04+1)