miwm-session: 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/bin/miwm-session - from package: miwm

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

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