GenSubjectAltNameExt: 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/GenSubjectAltNameExt - from package: pki-java-tools

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

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