dpkg-reconfigure: 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/sbin/dpkg-reconfigure - from package: debconf

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

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