jack_net_slave: 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/jack_net_slave - from package: jackd2

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

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