addgroup: 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/addgroup - from package: adduser

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

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