gfalFS_umount: 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/gfalFS_umount - from package: gfalFS

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

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