opener: 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/opener - from package: nodejs-opener

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

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