userlist: 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/sbin/userlist - from package: cfingerd

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

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