gmerlin-video-thumbnailer: 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/gmerlin-video-thumbnailer - from package: gmerlin

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

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