modupdate: 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/lib/wims/bin/modupdate - from package: wims

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

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