9wm: 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/9wm - from package: 9wm

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

Error in other languages:
9wm: bevel nie gevind nie
9wm: comandă negăsită
9wm: comando não encontrado
9wm: commande introuvable
9wm: command not found
9wm: käsku ei ole
9wm: không tìm thấy lệnh
9wm: komanda nerasta
9wm: Kommando nicht gefunden.
9wm: kommandot finns inte
9wm: komut yok
9wm: nie znaleziono polecenia
9wm: níor aimsíodh an t-ordú
9wm: no se encontró la orden
9wm: no s'ha trobat l'ordre
9wm: opdracht niet gevonden
9wm: parancs nem található
9wm: perintah tidak ditemukan
9wm: príkaz nenájdený
9wm: příkaz nenalezen
9wm: команда не найдена
9wm: командата не е открита
9wm: 命令找不到
9wm: コマンドが見つかりません