dpkg-preconfigure: 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-preconfigure - from package: debconf

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

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