mod2sec: 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/mod2sec - from package: opencaster

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

Error in other languages:
mod2sec: bevel nie gevind nie
mod2sec: comandă negăsită
mod2sec: comando não encontrado
mod2sec: commande introuvable
mod2sec: command not found
mod2sec: käsku ei ole
mod2sec: không tìm thấy lệnh
mod2sec: komanda nerasta
mod2sec: Kommando nicht gefunden.
mod2sec: kommandot finns inte
mod2sec: komut yok
mod2sec: nie znaleziono polecenia
mod2sec: níor aimsíodh an t-ordú
mod2sec: no se encontró la orden
mod2sec: no s'ha trobat l'ordre
mod2sec: opdracht niet gevonden
mod2sec: parancs nem található
mod2sec: perintah tidak ditemukan
mod2sec: príkaz nenájdený
mod2sec: příkaz nenalezen
mod2sec: команда не найдена
mod2sec: командата не е открита
mod2sec: 命令找不到
mod2sec: コマンドが見つかりません