get-cert: 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/get-cert - from package: isync

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

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