luserdel: 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 CentOS possible default full paths are:

/usr/sbin/luserdel - from package: libuser

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/luserdel - from package: libuser

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

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