deriving: 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/deriving - from package: libderiving-ocaml-dev

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