GlusterFS is already in available in Ubuntu's default apt repository which you can easily install using apt's install command though it's not necessarily the latest version. To install the latest version of GlusterFS via apt you'll need to use the gluster/glusterfs-5's PPA.

Follow these steps to install GlusterFS on Ubuntu:

1. Add GlusterFS ppa to apt (optional).

   $ sudo add-apt-repository ppa:gluster/glusterfs-5
   [sudo] password for user:
    GlusterFS 5
    More info: https://launchpad.net/~gluster/+archive/ubuntu/glusterfs-5
   Press [ENTER] to continue or Ctrl-c to cancel adding it.
   
   Get:1 http://ppa.launchpad.net/gluster/glusterfs-5/ubuntu cosmic InRelease [15.9 kB]
   Hit:2 http://archive.ubuntu.com/ubuntu cosmic InRelease
   Get:3 http://archive.ubuntu.com/ubuntu cosmic-updates InRelease [88.7 kB]
   Get:4 http://ppa.launchpad.net/gluster/glusterfs-5/ubuntu cosmic/main amd64 Packages [2,916 B]
   Get:5 http://archive.ubuntu.com/ubuntu cosmic-backports InRelease [74.6 kB]
   Get:6 http://ppa.launchpad.net/gluster/glusterfs-5/ubuntu cosmic/main Translation-en [772 B]
   Get:7 http://archive.ubuntu.com/ubuntu cosmic-security InRelease [88.7 kB]
   Get:8 http://archive.ubuntu.com/ubuntu cosmic-updates/main amd64 Packages [227 kB]
   Fetched 498 kB in 3s (198 kB/s)
   Reading package lists... Done

2. Update apt's package repository.

   $ sudo apt update

3. Install glusterfs-server package and required dependencies.

   $ sudo apt install -y glusterfs-server
   Reading package lists... Done
   Building dependency tree
   Reading state information... Done
   The following additional packages will be installed:
     attr glusterfs-client glusterfs-common ibverbs-providers keyutils libacl1-dev libaio1
     libattr1-dev libc-dev-bin libc6-dev libibverbs1 libnfsidmap2 libnl-route-3-200 librdmacm1
     libtirpc1 liburcu6 linux-libc-dev manpages-dev nfs-common python3-prettytable rpcbind
   Suggested packages:
     glibc-doc watchdog
   The following NEW packages will be installed:
     attr glusterfs-client glusterfs-common glusterfs-server ibverbs-providers keyutils
     libacl1-dev libaio1 libattr1-dev libc-dev-bin libc6-dev libibverbs1 libnfsidmap2
     libnl-route-3-200 librdmacm1 libtirpc1 liburcu6 linux-libc-dev manpages-dev nfs-common
     python3-prettytable rpcbind
   0 upgraded, 22 newly installed, 0 to remove and 0 not upgraded.
   Need to get 10.7 MB of archives.
     ##### snipped 

4. Configure glusterd to automatically start during system boot.

   $ sudo systemctl enable glusterd
   Created symlink /etc/systemd/system/multi-user.target.wants/glusterd.service → /lib/systemd/system/glusterd.service.

5. Start glusterd service.

   $ sudo systemctl start glusterd

6. Create highly available storage using GlusterFS (optional).

   [DRAFT] Create highly available storage with GlusterFS