Do you have a linux desktop computer?
deja-dup is a graphical client/browser for duplicity
EDIT:
Again do not think it is a path to the solution 
download the nethserver-7.5.1804 iso
https://sourceforge.net/projects/nethserver/files/nethserver-7.5.1804-x86_64.iso/download
install it DO NOT UPDATE
cat > /etc/yum.repos.d/CentOS-Base.repo << EOF
[base]
name=CentOS-$releasever - Base
baseurl=https://vault.centos.org/centos/7.5.1804/os/\$basearch/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
[updates]
name=CentOS-$releasever - Updates
baseurl=https://vault.centos.org/centos/7.5.1804/updates/\$basearch/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
[extras]
name=CentOS-$releasever - Extras
baseurl=https://vault.centos.org/centos/7.5.1804/extras/\$basearch/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
[centosplus]
name=CentOS-$releasever - Plus
baseurl=https://vault.centos.org/centos/7.5.1804/centosplus/\$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
EOF
and
cat > /etc/yum.repos.d/NethServer.repo << EOF
[nethserver-base]
name=NethServer-$releasever - Base
baseurl=http://mirror.nethserver.org/nethserver/7.5.1804/base/\$basearch/
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-NethServer-$releasever
enabled=1
enablegroups=0
[nethserver-updates]
name=NethServer-$releasever - Updates
baseurl=http://mirror.nethserver.org/nethserver/7.5.1804/updates/\$basearch/
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-NethServer-$releasever
enabled=1
enablegroups=1
[nethserver-testing]
name=NethServer-$releasever - Testing
baseurl=http://mirror.nethserver.org/nethserver/7.5.1804/testing/\$basearch/
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-NethServer-$releasever
enabled=0
enablegroups=0
EOF
Now you are pretty much locked on 7.5.1804
yum --enablerepo=* clean all
yum makecache
!!NOTE FOR ALL READERS!!
Do Not use this setup in production, it is unsecured and unstable!!!