network_restart: 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/lib/plainbox-providers-1/checkbox/bin/network_restart - from package: plainbox-provider-checkbox

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

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