mkvinfo-text: 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/mkvinfo-text - from package: mkvtoolnix

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

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