proofserva: 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/proofserva - from package: libroot-static

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

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