konwert: command not found

Have You tried accessing the binary with the full path?

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/konwert - from package: konwert

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