ntdbbackup: 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/ntdbbackup - from package: samba4-client

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

On Debian possible default full paths are:

/usr/bin/ntdbbackup - from package: ntdb-tools

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

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