arduino-add-groups: 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/bin/arduino-add-groups - from package: arduino

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

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