groupdel: 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/groupdel - from package: shadow-utils

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

On Debian possible default full paths are:

/usr/sbin/groupdel - from package: passwd

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

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