tpm_unloadkey: 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/tpm_unloadkey - from package: tpm-quote-tools

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

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