sha256hmac: 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/bin/sha256hmac - from package: hmaccalc

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

Error in other languages:
sha256hmac: bevel nie gevind nie
sha256hmac: comandă negăsită
sha256hmac: comando não encontrado
sha256hmac: commande introuvable
sha256hmac: command not found
sha256hmac: käsku ei ole
sha256hmac: không tìm thấy lệnh
sha256hmac: komanda nerasta
sha256hmac: Kommando nicht gefunden.
sha256hmac: kommandot finns inte
sha256hmac: komut yok
sha256hmac: nie znaleziono polecenia
sha256hmac: níor aimsíodh an t-ordú
sha256hmac: no se encontró la orden
sha256hmac: no s'ha trobat l'ordre
sha256hmac: opdracht niet gevonden
sha256hmac: parancs nem található
sha256hmac: perintah tidak ditemukan
sha256hmac: príkaz nenájdený
sha256hmac: příkaz nenalezen
sha256hmac: команда не найдена
sha256hmac: командата не е открита
sha256hmac: 命令找不到
sha256hmac: コマンドが見つかりません