gfm: 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/gfm - from package: gfm

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

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