opensipsctl: 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/sbin/opensipsctl - from package: opensips

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

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