tcpd: 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/tcpd - from package: tcp_wrappers

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

On Debian possible default full paths are:

/usr/sbin/tcpd - from package: tcpd
/usr/bin/tcpd - from package: tcm

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

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