dir2amp: 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/lib/mrtrix/bin/dir2amp - from package: mrtrix

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

Error in other languages:
dir2amp: bevel nie gevind nie
dir2amp: comandă negăsită
dir2amp: comando não encontrado
dir2amp: commande introuvable
dir2amp: command not found
dir2amp: käsku ei ole
dir2amp: không tìm thấy lệnh
dir2amp: komanda nerasta
dir2amp: Kommando nicht gefunden.
dir2amp: kommandot finns inte
dir2amp: komut yok
dir2amp: nie znaleziono polecenia
dir2amp: níor aimsíodh an t-ordú
dir2amp: no se encontró la orden
dir2amp: no s'ha trobat l'ordre
dir2amp: opdracht niet gevonden
dir2amp: parancs nem található
dir2amp: perintah tidak ditemukan
dir2amp: príkaz nenájdený
dir2amp: příkaz nenalezen
dir2amp: команда не найдена
dir2amp: командата не е открита
dir2amp: 命令找不到
dir2amp: コマンドが見つかりません