sg_referrals: command not found

Have You tried accessing the binary with the full path?

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/sg_referrals - from package: sg3-utils

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