cleanup_ANTS_warp: 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/cleanup_ANTS_warp - from package: mrtrix

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

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