derb: 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/bin/derb - from package: icu

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

On Debian possible default full paths are:

/usr/bin/derb - from package: icu-devtools

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

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