tcpflow: 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/tcpflow - from package: tcpflow-nox
/usr/bin/tcpflow - from package: tcpflow

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

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