jconvolver: 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/jconvolver - from package: jconvolver

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

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