pydb: 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/pydb - from package: pydb

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

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