mwm: 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 CentOS possible default full paths are:

/usr/bin/mwm - from package: lesstif-mwm
/usr/bin/mwm - from package: openmotif

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/mwm - from package: mwm

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

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