swanctl: 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/swanctl - from package: strongswan

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

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