usertree: 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/fastdnaml/bin/usertree - from package: fastdnaml

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

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