fwcheck_psad: 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/fwcheck_psad - from package: psad

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

On Debian possible default full paths are:

/usr/sbin/fwcheck_psad - from package: psad

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

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