gr_filter_design: 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/gr_filter_design - from package: gnuradio

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

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