setkey: 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:

/sbin/setkey - from package: ipsec-tools

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

On Debian possible default full paths are:

/usr/sbin/setkey - from package: ipsec-tools

You may install the required package with command apt-get install {package}

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