gst-feedback: 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/gst-feedback - from package: gstreamer-tools

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

On Debian possible default full paths are:

/usr/bin/gst-feedback - from package: gstreamer-tools

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

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