userlengths: 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/userlengths - from package: fastdnaml

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

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