mwdisext: 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/mwdisext - from package: mediawiki-extensions-base

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

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