pgrphack: 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/pgrphack - from package: daemontools

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

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