gmtkbabel: command not found

Have You tried accessing the binary with the full path?

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/gmtkbabel - from package: gmtkbabel

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