x509watch: 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 CentOS possible default full paths are:

/usr/bin/x509watch - from package: x509watch

You may install the required package with command yum install {package}

Error in other languages:
x509watch: bevel nie gevind nie
x509watch: comandă negăsită
x509watch: comando não encontrado
x509watch: commande introuvable
x509watch: command not found
x509watch: käsku ei ole
x509watch: không tìm thấy lệnh
x509watch: komanda nerasta
x509watch: Kommando nicht gefunden.
x509watch: kommandot finns inte
x509watch: komut yok
x509watch: nie znaleziono polecenia
x509watch: níor aimsíodh an t-ordú
x509watch: no se encontró la orden
x509watch: no s'ha trobat l'ordre
x509watch: opdracht niet gevonden
x509watch: parancs nem található
x509watch: perintah tidak ditemukan
x509watch: príkaz nenájdený
x509watch: příkaz nenalezen
x509watch: команда не найдена
x509watch: командата не е открита
x509watch: 命令找不到
x509watch: コマンドが見つかりません