gst-inspect: 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-inspect - 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-inspect - from package: gstreamer-tools

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

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