libopenvas-config: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/libopenvas-config - from package: openvas-libraries-devel

You may install the required package with command yum install {package}

Error in other languages:
libopenvas-config: bevel nie gevind nie
libopenvas-config: comandă negăsită
libopenvas-config: comando não encontrado
libopenvas-config: commande introuvable
libopenvas-config: command not found
libopenvas-config: käsku ei ole
libopenvas-config: không tìm thấy lệnh
libopenvas-config: komanda nerasta
libopenvas-config: Kommando nicht gefunden.
libopenvas-config: kommandot finns inte
libopenvas-config: komut yok
libopenvas-config: nie znaleziono polecenia
libopenvas-config: níor aimsíodh an t-ordú
libopenvas-config: no se encontró la orden
libopenvas-config: no s'ha trobat l'ordre
libopenvas-config: opdracht niet gevonden
libopenvas-config: parancs nem található
libopenvas-config: perintah tidak ditemukan
libopenvas-config: príkaz nenájdený
libopenvas-config: příkaz nenalezen
libopenvas-config: команда не найдена
libopenvas-config: командата не е открита
libopenvas-config: 命令找不到
libopenvas-config: コマンドが見つかりません