x509-util: 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/x509-util - from package: x509-util

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

Error in other languages:
x509-util: bevel nie gevind nie
x509-util: comandă negăsită
x509-util: comando não encontrado
x509-util: commande introuvable
x509-util: command not found
x509-util: käsku ei ole
x509-util: không tìm thấy lệnh
x509-util: komanda nerasta
x509-util: Kommando nicht gefunden.
x509-util: kommandot finns inte
x509-util: komut yok
x509-util: nie znaleziono polecenia
x509-util: níor aimsíodh an t-ordú
x509-util: no se encontró la orden
x509-util: no s'ha trobat l'ordre
x509-util: opdracht niet gevonden
x509-util: parancs nem található
x509-util: perintah tidak ditemukan
x509-util: príkaz nenájdený
x509-util: příkaz nenalezen
x509-util: команда не найдена
x509-util: командата не е открита
x509-util: 命令找不到
x509-util: コマンドが見つかりません