opensips: 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/opensips - from package: opensips

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

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