smartd: 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/smartd - from package: smartmontools

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

On Debian possible default full paths are:

/usr/sbin/smartd - from package: smartmontools

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

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