dpns-usage-by-vouser: 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/dpns-usage-by-vouser - from package: dpm-contrib-admintools

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

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