gmm: 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/cmtk/bin/gmm - from package: cmtk

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

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