tcptrack: 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 Debian possible default full paths are:

/usr/bin/tcptrack - from package: tcptrack

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

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