dhis-register-q: 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 Debian possible default full paths are:

/usr/sbin/dhis-register-q - from package: dhis-tools-dns

You may install the required package with command apt-get install {package}

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