ext: 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/picolisp/bin/ext - from package: picolisp

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

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