media-ctl: 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/media-ctl - from package: v4l-utils

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

On Debian possible default full paths are:

/usr/bin/media-ctl - from package: v4l-utils

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

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