.ipsec.hmac: 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/.ipsec.hmac - from package: libreswan
/usr/sbin/.ipsec.hmac - from package: openswan

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

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