streamtrack: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/streamtrack - from package: mrtrix

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